Katherine Springer Amey
Environmental Science, Physical Science, Geology, Physical Geography
Material Type:
College / Upper Division
  • Environmental Geology Textbook
  • Modern Science
  • Practical Applications
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    MODERN ENVIRONMENTAL GEOLOGY A Practical Textbook for the Modern Environmental Geologist

    MODERN ENVIRONMENTAL GEOLOGY A Practical Textbook for the Modern Environmental Geologist


    This textbook covers modern topics that environmental geologists encounter, including environmental laws, disasters, and climate change. 



    1. Introduction




    The environment includes the earth processes within the atmosphere, biosphere, hydrosphere, lithosphere and magnetosphere. Environmental geology is the study of the interaction between these earth processes and humans. Humans are both the agent of environmental impact by anthropogenic influence such as pollution and consumption, and the recipient of the earth’s forces such as natural disasters like flooding and earthquakes.


    The geologic environments differ across the planet, and there are varied interactions depending on the local geology and earth’s activities. The role of the environmental geologist is crucial in consulting, environmental remediation firms, research, industry, and local, state, and federal government agencies among others. Expertise is needed in the impacts of oil and mining, mineral and water resources, energy and soil and water pollution, and natural disasters such as earthquakes and volcanoes, floods, mass wasting and soil erosion. 


    From traditional environmental geology, long-associated with all facets of geology, rose the study of modern environmental geology in the mid 1970-80’s. The modern environmental geologist began to rise to the forefront of the profession in the United States dealing with issues of pollution, water quality and resources. The hydrogeologist is a relatively new facet of the environmental geologist as our understanding of groundwater increases. The national environmental movement was an impetus for a large portion of the focus of the modern environmental geologist.


    This environmental movement was initiated by a national consciousness that pollution was overcoming most of our earth's natural systems and something needed to be done. Many of the modern environmental geologist roles coincided with the formation of the U.S. Environmental Protection Agency (USEPA) in December 1970. Across the globe, environmental geologists are needed to solve complex environmental problems.

    The Origins of the Environmental Protection Agency (EPA) 


    Administrator William Ruckelshaus was the first federal administrator and  confirmed by the Senate on December 2, 1970, which is the traditional date we use as the birth of the agency. 

    Five months earlier, in July 1970, President Nixon had signed Reorganization Plan No. 3 calling for the establishment of EPA in July 1970.

    Two days after his confirmation, on December 4, Ruckelshaus took the oath of office and the initial organization of the agency was drawn up in EPA Order 1110.2.

    In the 1960s, the American national consciousness about environmental issues began to take hold. Rachel Carson wrote Silent Spring, in 1962 about the widespread and indiscriminate use of pesticides. After many disasters such as the Cuyahoga River starting on fire many times, oil spills, litter and pollution, concern about clean air and water was in the forefront. In 1970, under public pressure, President Richard Nixon presented the House and Senate a groundbreaking 37-point message on the environment.  

    Among these points included those especially relevant to the environmental geologist:

    • requesting four billion dollars for the improvement of water treatment facilities;

    • ordering a clean-up of federal facilities that had fouled air and water;

    • seeking legislation to end the dumping of wastes into the Great Lakes;

    • proposing a tax on lead additives in gasoline;

    • forwarding to Congress a plan to tighten safeguards on the seaborne transportation of oil; and

    • approving a National Contingency Plan for the treatment of oil spills.

    President Nixon also created a council to implement these points and organize the federal government to deal with this vast array of goals. The federal government was responsible for implementing these points, under the brand new Environmental Protection Agency.  The agency could address environmental problems now by researching important pollutants, monitor the environment and its impact on organisms and the physical environment, establish baselines to assess the success of pollution abatement, and in tandem with the states begin to enforce standards for air and water quality of individual pollutants, and industry would begin to have solutions for waste disposal. The federal agency would support the state agencies with financial, technical and training assistance.




    One of our biggest environmental problems facing the world today with far reaching effects is population growth. As more and more humans occupy our planet, the more demand for limited resources and the more demand for renewable energy and recycling. Without an endless supply of mineral resources and fossil fuels, we need to eventually face the dwindling supply, and manage our renewable resources.

    Not only is there a strain on valuable resources such as clean air and water but the growing population is increasing in areas of natural disasters, increasing the catastrophic impacts to life and the economy in those ever increasing urban centers.



    The US Census Bureau's world population clock in December 2022 estimates that the global population is 8,005,430,912  people. The world's population continues to increase every day with births outweighing deaths in most countries. On the averag globally, overall deaths per day being half of births per day.

    USA Trade Online (trade data).


    Overall, however, the rate of population growth has been slowing for several decades. This slowdown is expected to continue until the rate of population growth reaches zero (an equal number of births and deaths) around 2080-2100, at a population of approximately 10.4 billion people. After this time, the population growth rate is expected to turn negative, resulting in global population decline.


    December 2022 Most Populous Countries (Source: U.S. Census Bureau, International Database (demographic data) 


    Countries with more than 1 billion people

    China is currently the most populous country in the world, with a population estimated at more than 1.41 billion as of December 2022. India is not far behind, with a population is estimated to be 1.41 billion people, expected to replace China by 2030.


    Countries with more than 100 million people

    Another 12 countries each have populations that exceeded 100 million people as of December 2022:


    Country Population Country Population

    United States 338,653,036 Russia  144,704,502

    Indonesia 275,908,026 Mexico             127,724,673

    Pakistan 236,882,454 Japan             123,801,638

    Nigeria             219,741,895 Ethiopia 124,095,535

    Brazil             215,538,160             Philippines 115,969,226

    Bangladesh 171,594,827 Egypt             111,384,124


    A majority of countries in the world have less than 100 million people, but the world’s population continues to grow. The United Nations predicts global population will grow to 8.5 billion by 2030, 9.7 billion by 2050 and 10.4 by 2080. (World Population Prospects report)


    While the population growth rate is slowing, it will continue to rise until 2100, since global life expectancy has improved. The older population putting a strain on the economy. This imbalance can put considerable strain on a country's economy and infrastructure, as it can lead to a shortage of working-age individuals entering the workforce to take the place of those who are retiring. 


    Humans degrade and impact the physical environment in overpopulation, with increase in pollution, their carbon footprint, and deforestation. These changes are ever increasing climate change, loss of soil, water resource depletion and water quality degredation. In the United States, the demand for fast foods and decline of agriculture has impacted the environment in far reaching ways.





    Minerals are the building blocks of resources. Minerals are composed of elements and elements are composed of atoms(Figure 2-1).

    A mineral has requirements that it must meet to be classified a mineral.

    1. is a naturally occurring 

    2. inorganic element or compound 

    3. orderly internal structure  

    4. characteristic chemical composition, 

    5. crystalline structure

    6. physical properties. 


    Both metals and non-metals are used as resources in our daily lives.




    Atoms are made up of protons and neutrons and are surrounded by electrons. The atoms themselves are bonded together to make up the elements. More on atoms looking at unstable isotopes (different number of neutrons) in the periodic table.



    Periodic Table of Elements 

    USGS data (




    1. COLOR


    Mineral identification is completed through a series of characteristics of that mineral. Color is the least valuable when it comes to identification in a majority of minerals. Some minerals have characteristic colors, such as malachite (green) and azurite (blue), but minerals such as quarts come in a huge variety of colors.



    Specific gravity is the weight of the mineral when held in your hand. Mineralogists get quite good at identifying minerals by this property, or the ratio of a material's density with that of water at 4 °C.


    1. STREAK

    Streak is the color of minerals that is made on an unglazed porcelain surface. The streak color is characteristic of that mineral and the powder color made when brought along the surface, no matter the outside color. 


    1. LUSTER

    Luster is the overall shine or reflected light of its surface – it may be catagorized as metal, or non-metal. Examples of luster is that it looks “pearly”,  “glassy or vitreous” or “dull and earthy”.



    Cleavage is the tendency to break along planar surfaces of weakness. The description is usually given with a number of planes of cleavage and the angle. Fracture is when a mineral breaks with no apparent planar surface.


    A good example of cleavage is mica, which has one direction of cleavage and calcite with three directions of cleavage at 60 degrees and 120 degrees.


    A good example of fracture is quartz, which when broken does not break into any pattern. It does show a certain type of fracturing like conchoidal, but does not exhibit cleavage.



    The Mohs Hardness Scale is used to guage a mineral's hardness. Hardness is the ability to resist scratching on another substance listed on the Moh’s Hardness Scale:





    Additional properties such as magnetism, fluorescence, “The acid test” Yellow bubbles forming from the hydrochloric acid indicate that this sample is indeed carbonate. 


    How do we extract minerals?


    The USGS outlines the primary methods used to extract minerals from the ground are: 


    • Underground mining

    • Surface (open pit) mining

    • Placer mining 


    Many factors are pertinent to select which method of extraction to use. Where is it? What is the strength of the surrounding rock? Size? Cost? Ore grade (is it worth it?).


    More expensive underground methods are often used for ore bodies and higher-grade metallic ores found in veins deep under the Earth’s surface.  can be profitably mined using underground methods, which tend to be more expensive.  The rock is brought up to the surface and needs to be separated from the surrounding rock. 


    Surface mining methods are typically less expensive means to retrieve lower grade metal ores. Many industrial minerals are usually lower cost and are mined at the the Earth’s surface. Drilling and blasting is still used for minerals at the surface.


    Placer mining is a method of gathering  valuable minerals from sediments from river stream channels, beach sands, or ancient stream deposits. The mined material is washed and rinsed  to concentrate the heavier minerals.


    Common minerals include quartz, feldspar, mica, amphibole, olivine, and calcite. The USGS defines “critical minerals” as those that are significant to our energy needs and economy. The Department of the Interior updates and reviews the list.

    The Energy Act of 2020 defines a “critical mineral” as a non-fuel mineral or mineral material essential to the economic or national security of the U.S. and which has a supply chain vulnerable to disruption. Critical minerals are needed in manufacturing and essential day to day functioning.

    The current 2022 list of critical minerals via USGS includes the following — click a mineral’s name to find relevant statistics and publications:

    • Aluminum, used in almost all sectors of the economy

    • Antimony, used in lead-acid batteries and flame retardants

    • Arsenic, used in semi-conductors

    • Barite, used in hydrocarbon production.

    • Beryllium, used as an alloying agent in aerospace and defense industries

    • Bismuth, used in medical and atomic research

    • Cerium, used in catalytic converters, ceramics, glass, metallurgy, and polishing compounds

    • Cesium, used in research and development

    • Chromium, used primarily in stainless steel and other alloys

    • Cobalt, used in rechargeable batteries and superalloys

    • Dysprosium, used in permanent magnets, data storage devices, and lasers

    • Erbium, used in fiber optics, optical amplifiers, lasers, and glass colorants

    • Europium, used in phosphors and nuclear control rods

    • Fluorspar, used in the manufacture of aluminum, cement, steel, gasoline, and fluorine chemicals

    • Gadolinium, used in medical imaging, permanent magnets, and steelmaking

    • Gallium, used for integrated circuits and optical devices like LEDs

    • Germanium, used for fiber optics and night vision applications

    • Graphite , used for lubricants, batteries, and fuel cells

    • Hafnium, used for nuclear control rods, alloys, and high-temperature ceramics

    • Holmium, used in permanent magnets, nuclear control rods, and lasers

    • Indium, used in liquid crystal display screens

    • Iridium, used as coating of anodes for electrochemical processes and as a chemical catalyst

    • Lanthanum, used to produce catalysts, ceramics, glass, polishing compounds, metallurgy, and batteries

    • Lithium, used for rechargeable batteries

    • Lutetium, used in scintillators for medical imaging, electronics, and some cancer therapies

    • Magnesium, used as an alloy and for reducing metals

    • Manganese, used in steelmaking and batteries

    • Neodymium, used in permanent magnets, rubber catalysts, and in medical and industrial lasers

    • Nickel, used to make stainless steel, superalloys, and rechargeable batteries

    • Niobium, used mostly in steel and superalloys

    • Palladium, used in catalytic converters and as a catalyst agent

    • Platinum, used in catalytic converters

    • Praseodymium, used in permanent magnets, batteries, aerospace alloys, ceramics, and colorants

    • Rhodium, used in catalytic converters, electrical components, and as a catalyst

    • Rubidium, used for research and development in electronics

    • Ruthenium, used as catalysts, as well as electrical contacts and chip resistors in computers

    • Samarium, used in permanent magnets, as an absorber in nuclear reactors, and in cancer treatments

    • Scandium, used for alloys, ceramics, and fuel cells

    • Tantalum, used in electronic components, mostly capacitors and in superalloys

    • Tellurium, used in solar cells, thermoelectric devices, and as alloying additive

    • Terbium, used in permanent magnets, fiber optics, lasers, and solid-state devices

    • Thulium, used in various metal alloys and in lasers

    • Tin, used as protective coatings and alloys for steel

    • Titanium, used as a white pigment or metal alloys

    • Tungsten, primarily used to make wear-resistant metals

    • Vanadium, primarily used as alloying agent for iron and steel

    • Ytterbium, used for catalysts, scintillometers, lasers, and metallurgy

    • Yttrium, used for ceramic, catalysts, lasers, metallurgy, and phosphors

    • Zinc, primarily used in metallurgy to produce galvanized steel

    • Zirconium, used in the high-temperature ceramics and corrosion-resistant alloys.

    Global Mineral Sources

    Globally, mineral resources are found on every continent. USGS has interactive global maps to locate mineral resources known and mined.





    How much is needed?

    Of interest to us in the United States are how much is a supply of minerals needed for the average person during their lifetime? 

    According to the USGS, at today's level of consumption, the average newborn infant will need a lifetime supply of: 

    • 871 pounds of lead 

    • 502 pounds of zinc 

    • 950 pounds of copper 

    • 2,692 pounds of aluminum 

    • 21,645 pounds of iron ore 

    • 11,614 pounds of clays 

    • 30,091 pounds of salt 

    • 1,420,000 pounds of stone, sand, gravel, and cement 



    A rock is made from one or more minerals, or a body of undifferentiated mineral matter. 

    Common rocks include igneous, metamorphic and sedimentary.


    What are igneous rocks?

    Igneous rocks (Ignis=latin for fire) form when hot, molten rock crystallizes and solidifies, either at or below the surface.  Igneous rocks are divided into two main groups, intrusive or extrusive:

    Intrusive Igneous Rocks:


    Intrusive, or plutonic, igneous rock forms when molten “magma” is cooled below the surface. This cooling may take many thousands or millions of years until it solidifies. Slow cooling means the individual mineral grains have a very long time to grow, so they grow to a relatively large size and are considered course grained texture.

    Extrusive Igneous Rocks:

    Extrusive, or volcanic, igneous rock is produced when magma exits as lava and cools above (or very near) the Earth's surface. This cooling and solidifying takes place rapidly due to the large difference in atmospheric temperatures.  Think of a glass blower! These rocks are very fine-grained or even have a glassy texture. 

    Composition also differs with felsic and mafic textures. In general, felsic are the lighter in color and higher in silica (common exception is basalt that is felsic but black). Mafic igneous rocks are higher in metals and lower in silica.


    What are metamorphic rocks?

    Metamorphic rocks are changed rocks. They began as a protolith of another type of rock, either igneous, metamorphic or sedimentary, but changed. 


    Metamorphic rocks form from high temperature, pressure, or fluids or all three! The rocks are changed but not melted but by different processes 


    The process of metamorphism does not melt the rocks, but instead transforms and changes them them into denser, more compact rocks. There are two main types of metamorphic rocks, either foliated or unfoliated.


    Foliated Metamorphic Rocks:

    Foliation is a texture that forms from pressure making a parallel arrangement of mineral grains that align. These rocks exhibit orientation perpendicular to the force of pressure. Elongated minerals develop a platy or sheet-like structure in the new rock.


    Non-Foliated Metamorphic Rocks:

    Non-foliated metamorphic rocks are made from equant minerals that do not align. Often there is very high temperature changing the rock, especially exhibited in contact metamorphism, where the rocks surrounding a magma chamber are changed and baked. This mineral structure is changed with lower pressure.


    Close up of Garnet Schist


    What are sedimentary rocks?

    Image: Sandstone Detail

    Sedimentary rocks form near the earth’s surface and are classified as clastic, made from the weathering of other rocks, are non-clastic chemical formed by sediments “glued” by chemical means, or  from fossils biologic or organic from once living organisms. Sedimentary rocks have bedding or are typically laid in water in layers.


    Clastic Sedimentary Rocks:


    Clastic sedimentary rocks are made up of clasts of rocks that have been set in motion by weathering and erosion, transportation and lithification. Lithification involves deposition, then compaction and cementation. Clastic sedimentary rocks are classified based on their clasts and grain size. The smallest grains are called clay, then silt, then sand. Grains larger than 2 millimeters are called pebbles. 


    Chemical Sedimentary Rocks

    Chemical sedimentary rocks are formed out of a solution of water, ions, and sediment and are formed by processes like evaporation of water or  the precipitation of ions.


    Organic Sedimentary Rocks

    Organic sedimentary rocks are formed from organic matter that has been compressed over time such as coal, which is from compressed plant matter.


    Biologic Sedimentary Rocks:

    Biologic sedimentary rocks form when large numbers of living things die. They are made of biologic materials from living organisms like coquina, which is made up of shells.





    A primary source of energy is by the combustion of fossil fuels like oil, coal and natural gas. Additional sources of energy to a lower extent include nuclear energy (nuclear fission)  and renewable energy like wind, solar, geothermal and hydropower. 


    These primary sources are converted to electricity and can be locality dependant.


    Fossil energy sources


    These fossil energy sources including oil, coal and natural gas, are non-renewable resources. The organic matter was buried in the past as plants and animals and the rich carbon source developed over millions of years. 


    According to the DOE, nearly three-fourths of emissions is from the burning of fossil fuels in the past 20 years.


    The Energy Department is responsible to develop oil and gas sources,  maintains emergency petroleum reserves, and regulates the industry..


    Coal is the largest domestically produced source of energy in America and is used to generate a significant amount of our nation’s electricity. The Department is also investing in development of carbon capture, utilization and storage (CCUS) technologies, also referred to as carbon capture, utilization and sequestration.


    Oil-Oil is used for heating and transportation -- a majority for gas-powered vehicles. America’s dependence on foreign oil has declined in recent years, but oil prices have increased.


    The Energy Department supports research and policy options to increase our domestic supply of oil while ensuring environmentally sustainable supplies domestically and abroad, and is investing in research, technology and processes to make oil drilling cleaner and more efficient -- including enhanced oil recovery and improved offshore drilling practices.



    Natural gas is an abundant resource across the United States, making us the world’s leader in natural gas producing. Shale gas development has increased with fracking and extraction of natural gas. 

    Methane hydrates have been used to develop natural gas, but methane is a very efficient greenhouse gas.  Natural gas-powered alternative fuel vehicles have been investigated.


    Nuclear Power

    Nuclear Energy (Photo Amey)


    20% of energy in the United States is generated from nuclear power. The U.S. has used nuclear power for greater than 60 years. It is completed by nuclear fission and it is considered a “clean energy source” although there is concern with both the consequences of nuclear accidents as well as nuclear waste.


    Renewable Energy Resources


    The U.S. renewable energy sector is growing and the country would greatly benefit from expanding these sources of energy. The energy resources include solar, wind, water, geothermal, & bioenergy. 


    Solar energy converts sunlight into electrical energy either through photovoltaic (PV) panels or through mirrors that concentrate solar radiation. The Solar Energy Technologies Office (SETO) funds research and development across the solar energy spectrum to drive innovation, lower costs, and support the transition to a decarbonized power sector by 2035 and a decarbonized economy by 2050. Costs for these continue to come down and are becoming more common among businesses and residences.


    Wind energy is growing in the United States and is one of the largest and fastest-growing wind markets in the world.

    The Block Island Wind Farm is one of the first U.S. offshore wind farms, and generates an enormous amount of energy. Coastal cities have a large potential for wind energy.


    Coal is the largest domestically produced source of energy in America and is used to generate a significant amount of our nation’s electricity.

    Water and geothermal energy are beneficial sources of renewable energy; however are highly location dependant. Hydropower can cause problems for spawning migration and other wildlife, and is increasingly focused on new sources such emerging technologies to advance marine tidal energy  and river current as well as next generation hydropower and pumped storage systems for a flexible, reliable grid. Geothermal energy must be in a tectonically active environment.


    Bioenergy or Biomass is an organic renewable energy source that includes materials such as agriculture and forest residues, energy crops, and algae. Ways to convert biomass into biofuels have been introduced and have not as yet replaced fossil fuels like gasoline, diesel, and jet fuel.





    The earth is divided into several separate lithospheric plates of crusts and the upper mantle. Plates were originally postulated by Alfred Wegener, a Scientist who saw that the continents at one time fit together like a jigsaw puzzle. In addition across continents there were matching rock units, mountains and fossils. There was also climatic evidence that showed the similarities in climate across continents. He could not determine a mechanism for this theory, which he termed “continental drift”.


    Scientists now have a fairly good understanding of how the plates move and how such movements relate to earthquake activity. Most movement occurs along narrow zones between plates where the results of plate-tectonic forces are most evident.


    There are four types of plate boundaries:


    1. Divergent boundaries -- where new crust is generated as the plates pull away from each other.

    2. Convergent boundaries -- where crust is destroyed as one plate dives under another.

    3. Transform boundaries -- where crust is neither produced nor destroyed as the plates slide horizontally past each other.


    Artist's cross section illustrating the main types of plate boundaries (see text); East African Rift Zone is a good example of a continental rift zone. (Cross section by José F. Vigil from This Dynamic Planet -- a wall map produced jointly by the U.S. Geological Survey, the Smithsonian Institution, and the U.S. Naval Research Laboratory.)


    1. Divergent boundaries

    Divergent boundaries occur along spreading centers where lithospherric plates are spreading apart and new crust is being formed by magma pushing up from the mantle. Away from the ridge on either side the crust is pushed away from the center ridge. These are called mid ocean ridges (MOR), and often the ridge is named for the ocean that contains the ridge, For example, a well known MOR in the Atlantic is the Mid-Atlantic Ridge.The underwater volcano ridge starts at the Arctic Ocean and reaches down to Africa.


    The rate of spreading along the Mid-Atlantic Ridge averages about 2.5 centimeters per year (cm/yr), or 25 km in a million years. This rate may seem slow by human standards, but because this process has been going on for millions of years, it has resulted in plate movement of thousands of kilometers. Seafloor spreading over the past 100 to 200 million years has caused the Atlantic Ocean to grow from a tiny inlet of water between the continents of Europe, Africa, and the Americas into the vast ocean that exists today.

    Mid-Atlantic Ridge gif

    Mid-Atlantic Ridge (USGS)


    The Azores and the volcanic country of Iceland, straddle the Mid-Atlantic Ridge, The plates move apart and diverge from either side of the ridge.

    Map showing the Mid-Atlantic Ridge splitting Iceland and separating the North American and Eurasian Plates. The map also shows Reykjavik, the capital of Iceland, the Thingvellir area, and the locations of some of Iceland's active volcanoes (red triangles), including Krafla. You can walk through this area if you go to Iceland! (USGS)

    The plate divide near the Reykjanes Peninsula in Icleand (Katherine Amey)


    The consequences of plate movement are easy to see around Krafla Volcano, in the northeastern part of Iceland. Here, existing ground cracks have widened and new ones appear every few months. From 1975 to 1984, numerous episodes of rifting (surface cracking) took place along the Krafla fissure zone. Some of these rifting events were accompanied by volcanic activity; the ground would gradually rise 1-2 m before abruptly dropping, signalling an impending eruption. Between 1975 and 1984, the displacements caused by rifting totalled about 7 m.

    Lava Fountains, Krafla Volcano (USGS)

    Thingvellir fissure zone gif

    Thingvellir fissure zone gif Thingvellir Fissure Zone, Iceland USGS)


    In East Africa, spreading processes have already torn Saudi Arabia away from the rest of the African continent, forming the Red Sea. The actively splitting African Plate and the Arabian Plate meet in what geologists call a triple junction, where the Red Sea meets the Gulf of Aden. 


    When Plate boundaries on land spread apart they are called a rift valley. A new spreading center may be developing under Africa along the East African Rift Zone. When the continental crust stretches beyond its limits, tension cracks begin to appear on the Earth's surface. Magma rises and squeezes through the widening cracks, sometimes to erupt and form volcanoes. The rising magma, whether or not it erupts, puts more pressure on the crust to produce additional fractures and, ultimately, the rift zone.

    East Africa volcanoes gif Historically Active Volcanoes, East Africa (USGS)


    East Africa may be ta new ocean in the future. By studying this area, geologists can study how the Atlantic began to form about 200 million years ago. Geologists believe that, if spreading continues, the three plates that meet at the edge of the present-day African continent will separate completely, allowing the Indian Ocean to flood the area and making the easternmost corner of Africa (the Horn of Africa) a large island.

    Erta Ale gif

     Summit Crater of 'Erta 'Ale (USGS)

    Oldoinyo Lengai gif

    Oldoinyo erupts gif Oldoinyo Lengai, East African Rift Zone (USGS)


    1. Convergent boundaries

    Convergent boundaries are considered destruction (recycling) of crust where plates are moving toward each other, and sometimes one plate sinks is subducted or sinks under another. The location where sinking of a plate occurs is called a subduction zone. The oceanic plate, due to being very dense always sinks below the lighter continental crust.


    Convergence can occur between:


    An oceanic and a continental plate O-C

    Two oceanic plates O-O

    Two continental plates. C-C


    Oceanic-continental convergence O-C

    Off the coast of South America, the oceanic Nazca Plate is being subducted under the continental part of the South American Plate. In turn, the overriding South American Plate is being lifted up, creating the towering Andes mountains, the backbone of the continent. Strong, destructive earthquakes and the rapid uplift of mountain ranges are common in this region. Even though the Nazca Plate as a whole is sinking smoothly and continuously into the trench, the deepest part of the subducting plate breaks into smaller pieces that become locked in place for long periods of time before suddenly moving to generate large earthquakes. Such earthquakes are often accompanied by uplift of the land by as much as a few meters.

    Nazca-SoAm plates gif

    Nazca-SoAm gif Convergence of the Nazca and South American Plates (USGS)


    On 9 June 1994, a magnitude-8.3 earthquake struck about 320 km northeast of La Paz, Bolivia, at a depth of 636 km. This earthquake, within the subduction zone between the Nazca Plate and the South American Plate, was one of deepest and largest subduction earthquakes recorded in South America. Fortunately, even though this powerful earthquake was felt as far away as Minnesota and Toronto, Canada, it caused no major damage because of its great depth.


    In addition the subduction zones generate volcano activity parallel to the boundary. So much so on the Pacific Boundary it is called the Ring of Fire like the Andes and the Cascade Range in the Pacific Northwest

     Ring of Fire (USGS)

    Oceanic-oceanic convergence O-O

    As with oceanic-continental convergence, when two oceanic plates converge, one is usually subducted under the other, and in the process a deep trench is formed. The Marianas Trench (paralleling the Mariana Islands), for example, marks where the fast-moving Pacific Plate converges against the slower moving Philippine Plate. The Challenger Deep, at the southern end of the Marianas Trench, plunges deeper into the Earth's interior (nearly 11,000 m) than Mount Everest, the world's tallest mountain, rises above sea level (about 8,854 m).



    Subduction processes in oceanic-oceanic plate convergence also result in the formation of volcanoes along in a curved chain called an island arc. Over millions of years, the erupted lava and volcanic debris pile up on the ocean floor until a submarine volcano rises above sea level to form an island volcano. 


    The trenches are the key to understanding how island arcs such as the Marianas and the Aleutian Islands have formed and why they experience numerous strong earthquakes. 

    Magmas that form island arcs are produced by the partial melting of the descending plate and/or the overlying oceanic lithosphere. The descending plate also provides a source of stress as the two plates interact, leading to frequent moderate to strong earthquakes.


    Continental-continental convergence C-C

    When two lighter continental plates meet they tend to collide and are pushed upward or sideways. The collision of India into Asia 50 million years ago caused the Indian and Eurasian Plates to crumple up along the collision zone. The Himalayan mountain range shows one of the most recent amazing collisions.


    After the collision, the slow continuous convergence of these two plates over millions of years pushed up the Himalayas and the Tibetan Plateau to their present heights. Most of this growth occurred during the past 10 million years. The Himalayas, towering as high as 8,854 m above sea level, form the highest continental mountains in the world. Moreover, the neighboring Tibetan Plateau, at an average elevation of about 4,600 m, is higher than all the peaks in the Alps except for Mont Blanc and Monte Rosa, and is well above the summits of most mountains in the United States.




    Above: The collision between the Indian and Eurasian plates has pushed up the Himalayas and the Tibetan Plateau. Below: Cartoon cross sections showing the meeting of these two plates before and after their collision. The reference points (small squares) show the amount of uplift of an imaginary point in the Earth's crust during this mountain-building process (USGS).




     The Himalayas: Two Continents Collide (USGS)


    1. Transform boundaries

    The zone between two plates sliding horizontally past one another is called a transform-fault boundary, or simply a transform boundary. Most transform faults are found on the ocean floor. They commonly offset the active spreading ridges, producing zig-zag plate margins, and are generally defined by shallow earthquakes. 


    However, a few occur on land, for example the large San Andreas fault zone in California is also a transform plate boundary. This transform fault connects the East Pacific Rise, a divergent boundary to the south, with the South Gorda -- Juan de Fuca -- Explorer Ridge, another divergent boundary to the north.

    The Blanco, Mendocino, Murray, and Molokai fracture zones are some of the many fracture zones (transform faults) that scar the ocean floor and offset ridges (see text). The San Andreas is one of the few transform faults exposed on land (USGS).


    The San Andreas fault zone, which is about 1,300 km long and in places tens of kilometers wide, slices through two thirds of the length of California. Along it, the Pacific Plate has been grinding horizontally past the North American Plate for 10 million years, at an average rate of about 5 cm/yr. Land on the west side of the fault zone (on the Pacific Plate) is moving in a northwesterly direction relative to the land on the east side of the fault zone (on the North American Plate).

    San Andreas fault gif

    San Andreas gif San Andreas fault (USGS)


    Oceanic fracture zones are ocean-floor valleys that horizontally offset spreading ridges; some of these zones are hundreds to thousands of kilometers long and as much as 8 km deep. Examples of these large scars include the Clarion, Molokai, and Pioneer fracture zones in the Northeast Pacific off the coast of California and Mexico. These zones are presently inactive, but the offsets of the patterns of magnetic striping provide evidence of their previous transform-fault activity.


    Rates of motion

    We can measure how fast tectonic plates are moving today, but how do scientists know what the rates of plate movement have been over geologic time? The oceans hold one of the key pieces to the puzzle. Because the ocean-floor magnetic striping records the flip-flops in the Earth's magnetic field, scientists, knowing the approximate duration of the reversal, can calculate the average rate of plate movement during a given time span. These average rates of plate separations can range widely. The Arctic Ridge has the slowest rate (less than 2.5 cm/yr), and the East Pacific Rise near Easter Island, in the South Pacific about 3,400 km west of Chile, has the fastest rate (more than 15 cm/yr).

    monolith gif

    monolith gif Easter Island monolith (USGS)


    Evidence of past rates of plate movement also can be obtained from geologic mapping studies. If a rock formation of known age -- with distinctive composition, structure, or fossils -- mapped on one side of a plate boundary can be matched with the same formation on the other side of the boundary, then measuring the distance that the formation has been offset can give an estimate of the average rate of plate motion. This simple but effective technique has been used to determine the rates of plate motion at divergent boundaries, for example the Mid-Atlantic Ridge, and transform boundaries, such as the San Andreas Fault.

    GPS satellite gif

    GPS satellite gif GPS Satellite and Ground Receiver (USGS)


    Plate movement are tracked by ground methods but they are currently measured by satellite-based methods. The three most commonly used space-geodetic techniques -- very long baseline interferometry (VLBI), satellite laser ranging (SLR), and the Global Positioning System (GPS) -- are based on technologies developed for military and aerospace research, notably radio astronomy and satellite tracking. GPS tracking has been widely used for tracking the earth’s plate movements. 21 satellites 20,000 km above the earth;s surface transmit data on a continuous basis. The rates and directions of plate movements have been confirmed and geologists are hoping this information will help to learn more about activity especially in the ring of fire, and the chain of events leading to the eruption of volcanoes and movement before earthquakes.



    What is a volcano?

    Volcanoes are vents where lava, tephra (small rocks), and steam erupt onto the Earth's surface. Volcanic eruptions can last days, months, or even years.  

     Redoubt volcano with minor ash eruption. Photograph taken during observation and gas data collection flight by AVO staff March 30, 2009 (USGS)


    Volcanoes shape the landscape depending on the type of eruption they have. As the lava erupts it accumulates and solidifies to a characteristic shape. The volcano erupts until it is no longer stable and can collapse and have landslides.


    How do volcanoes erupt?

    Illustration of the basic process of magma formation, movement to the surface, and eruption through a volcanic vent (USGS)


    Molten rock below the surface of the Earth that rises in volcanic vents is known as magma, but after it erupts from a volcano it is called lava. Magma is made of molten rock, crystals, and dissolved gas— The molten rock is made of melted magma of different composition, depending on the source rock and temperature. After cooling, liquid magma may form crystals of various minerals until it becomes completely solid and forms an igneous or magmatic rock.


    From the mantle, the less dense magma rises to the surface by buoyancy, it is lighter than the surrounding rock, and gas within has pressure to force upward and may reach the surface as an eruption. 

    HVO geologist carries a freshly quenched lava sample from the 2011 Kamoamoa fissure eruption on Kīlauea Volcano. Molten lava is quickly placed in a bucket of water to "freeze" the growth of minerals for chemical and microscopic analyses (USGS).


    Lava may erupt in many different ways. It may be explosive or effusive in its eruption. 


    if it has a magma that is more felsic, or high silica, it will be more viscous and have high gasses in the magma, thus it will be more explosive. The explosion may include more pyroclastic debris and have a dense cloud of ash and gasses that are taken up and travel in the atmosphere.


    The more effusive eruption is found with the more mafic magma, that is hotter, less silica, and the gasses have escapted. 





















    How many volcanoes are there?


    USGS scientists monitor over 160 active and potentially active volcanoes in the United States. Most of these volcanoes are located in the western Pacific, in the "Ring of Fire." The state with the greatest activity is mainly Alaska, a state where eruptions occur almost every year. Hawaii Kīlauea volcano on the Island of Hawai‘i is one of the most active volcanoes on Earth. It has been erupting almost nonstop since 1983!

    There are about 1,350 potentially active volcanoes worldwide, and less than half of these have erupted in the past 100 years. In the U.S., volcanoes along the west coast and in Alaska (Aleutian volcanic chain) are part of the Ring of Fire, while Yellowstone and Hawaiian volcanoes form over a "hot spot."


    What are the main types of volcanoes?


    Cinder Cone

    SP Crater and lava flow (dark area to right of cinder cone) in the northern part of San Francisco Volcanic Field, Arizona. (USGS).


    Cinder cones are from a single volcano eruption of small pieces of cinder, or solid lava. A  powerful blast throws molten rocks, ash, and gas into the air. The rocks cool quickly in the air and fall to the earth to break into small pieces of bubbly cinder that pile up around the vent. 


    Composite Volcano (Stratovolcano)


    East Summit is on the left skyline, and North Summit, to its right, is topped by an ice-filled crater from which a blocky dacite lava flow extends 1 km toward the camera. Central summit, the highest point on the mountain at just over 7,100 ft (2,165 m) rises on the background skyline, 7 km southwest of North Summit. Alaska Volcano Observatory photo (USGS)


    Composite volcanoes are also called stratovolcanoe because they are made from layers of ash, debris and lava over time. These volcanos are typically in the shape of a cone that you normally think of with the term volcano.. Some composite volcanoes rise over 8,000 feet above sea level.. Ojos del Salado in Chile is the tallest composite volcano on Earth with a summit elevation of 22,615 feet; the tallest in the U.S. is Mount Rainier in Washington State with a summit elevation of 14,410 feet. 


    Shield Volcano

    Shield-volcano Mauna Kea viewed from the northern slope of Mauna Loa (cinder cones in the foreground) shows off its broad shield shape. The bumps on its profile are large cinder cones


    Shield volcanoes are formed from fast flowing effusive lava. The lava flows fast and far and with each eruption layers overlap to make a shape like an upside down shield. The volcano has a shallow slope due to the nature of the lava and forms a massive volcano.


    In northern California and Oregon, many shield volcanoes are up to 3 or 4 miles wide and as tall as 1,500 to 2,000 feet. The Hawaiian Islands are made of a chain of shield volcanoes including Kīlauea and the world's largest active volcano, Mauna Loa.


    Lava Dome

    A lava dome is an  eruption phenomenon that builds when lava is too thick to flow away from the vent. Some domes form pointy spines, while others appear as a giant muffin, as opening flower petals, or as steep-sided stubby flows or tongues. Lava domes often grow within craters or upon the flanks of large steep-sided composite volcanoes. Lava domes can be dangerous. They grow largely by expansion from within. As fresh magma fills the inside, the cooler and harder outer surface shatters and spills hot rock and gases down the mountainside.




    What is an earthquake? 

    An earthquake is what happens when two blocks of the earth that have been “stuck”  suddenly slip past one another. The surface where they slip is called the fault or fault plane. The location below the earth’s surface where the earthquake starts is called the hypocenter, and the location directly above it on the surface of the earth is called the epicenter.

    cartoon of two blocks of offset earth crust at an angle

    A normal (dip-slip) fault is an inclined fracture where the rock mass above an inclined fault moves down (USGS).

    Sometimes an earthquake has foreshocks and aftershocks. These are smaller earthquakes that happen before and after the earthquake respectively in the same place as the larger earthquake (mainshock). Aftershocks can continue for weeks, months, and even years after the mainshock!



    What causes earthquakes and where do they happen?

    cartoon of cutout wedge of earth

    A simplified cartoon of the crust (brown), mantle (orange), and core (liquid in light gray, solid in dark gray) of the earth. (USGS)

    The core of the earth was the first internal structural element to be identified. In 1906 R.D. Oldham discovered it from his studies of earthquake records. The inner core is solid, and the outer core is liquid and so does not transmit the shear wave energy released during an earthquake. 

    The earth has four major layers: the inner core, outer core, mantle and crust. The crust and the upper mantle make up the lithosphere that is what the tectonic plates are made of. The plate boundaries are made up of many faults, and most of the earthquakes around the world occur on these faults, although they often occur intraplate as well. The tectonic movement instigates activity between tectonic plates and often strikes earthquakes.

    The majority of the earthquakes and volcanic eruptions occur along plate boundaries such as the boundary between the Pacific Plate and the North American plate. One of the most active plate boundaries where earthquakes and eruptions are frequent, for example, is around the massive Pacific Plate commonly referred to as the Pacific Ring of Fire.

    map of Earth in puzzle pieces

    The tectonic plates divide the Earth's crust into distinct "plates" that are always slowly moving. Earthquakes are concentrated along these plate boundaries. (USGS)


    Why does the earth shake when there is an earthquake?

    While there are seismic gaps in earthquakes, or times when they don’t occur for a long time. When the blocks are stuck together energy is stored and when the force of friction is overcome and it is “unstuck” an enormous amount of energy is released in seismic waves. 

    The seismic waves shake the earth as body waves move through it, and surface waves shake the ground and any infrastructure.

    When the earthquakes happen and stress is applied,  sometimes there is a rebound to the original state. When it goes past the elastic limit it will sometimes show strain and deformation.

    Think of a rubber band, the stretch the earth’s surface, they shake the ground and anything on it, like our houses and us!past he elastic limit.


    How are earthquakes recorded?

    Cartoon sketch of seismograph

    The cartoon sketch of the seismograph shows how the insrument shakes with the earth below it, but the recording device remains stationary (instead of the other way around). (USGS)

    Seismographs record earthquakes and they record a seismogram. Shaking is detected and seismograms show the arrival of the two main types of seismic waves, body waves and surface waves.

    Body waves that go through the earth: 

    The first body wave to arrive is a P wave or primary wave and the P wave travels the fastest through both solids and liquids. The waves move in a compression wave in the direction of travel and alternately compresses and expands.

    The second body wave is an S wave or shear wave. The S wave only travels through solids. It oscillates up and down (vertically)  in the direction of the wave.

    cartoon of two cross-sections of crust

    P Waves alternately compress and stretch the crustal material parallel to the direction they are propagating. S Waves cause the crustal material to move back and forth perpendicular to the direction they are travelling. (USGS)

    Surface waves on the surface of the earth

    The third wave to arrive that travels along the surface is referred to as the L wave or love wave. It travels side to side like a snake 

    The fourth wave and most damaging is the R wave or Rayleigh Wave, which have a rolling motion-and up and down.




    How do scientists measure the size of earthquakes?

    squiggly line

    An example of a seismic wave with the P wave and S wave labeled. (USGS)

    The size of an earthquake depends on the size of the fault and the amount of slip on the fault recorded on the seismogram. Ultimately the amplitude of the wave may be used with the larger amplitude indicating a larger earthquake, but you begin with the difference in the arrival time  the P and S wave called the lag time. This information is required from at least three seismic stations to assure triangulation for determining the location of the earthquake. The closer distance the seismic station, the faster the P wave will arrive, and if you are farther away the more time for the P wave to arrive and the lag between the arrival of the P and S wave.

    The information shows how far away it was but not where the epicenter was. If you draw a circle around the station where the radius of the circle is determined to be the distance to the earthquake. Triangulation is  used to pinpoint where the  intersection of the three circles, or the epicenter!

    map of U.S. with dots and circles

    Triangulation can be used to locate an earthquake. The seismometers are shown as green dots. The calculated distance from each seismometer to the earthquake is shown as a circle. The location where all the circles intersect is the location of the earthquake epicenter. (USGS)

    Earthquake Predictability

    There are signs of an earthquake by looking at past areas of activity and location, but overall they are unpredictable. Weather may change and affect earthquake occurrence, and some animals or people can tell when an earthquake is coming, but more research is needed to determine the correlations.

    There are different scales of measurement for earthquakes. The Richter scale is the most widely recognized scale, but scientists use the Moment Magnitude scale to distinguish between larger earthquakes. 


    The Mercalli Index is a scale that is a Roman numeral scale based on the amount of damage an earthquake causes.

    The largest recorded earthquake in the United States was a magnitude 9.2 that struck Prince William Sound, Alaska on Good Friday, March 28, 1964 UTC. Alaska is the most earthquake-prone state and one of the most seismically active regions in the world. Alaska experiences a magnitude 7 earthquake almost every year, and a magnitude 8 or greater earthquake on average every 14 years.

    Peter Haeussler measuring offset snowpack caused by the M7.9 Denali, Alaska earthquake on November 3, 2002.

    Peter Haeussler prepares to measure the offset of a crevasse on the Canwell Glacier, Alaska, USA. Photo by Peter Haeussler, USGS, November 9, 2002 (Public domain.)


    The largest recorded earthquake in the world was a magnitude 9.5 (Mw) in Chile on May 22, 1960. 

    map of Pacific Ocean with areas around the perimeter shaded

    Volcanic arcs and oceanic trenches partly encircling the Pacific Basin form the so-called Ring of Fire, a zone of frequent earthquakes and volcanic eruptions. The trenches are shown in blue-green. The volcanic island arcs, although not labelled, are parallel to, and always landward of, the trenches. For example, the island arc associated with the Aleutian Trench is represented by the long chain of volcanoes that make up the Aleutian Islands. (USGS). 

    The “Ring of Fire” also called the Circum-Pacific belt, is the zone of earthquakes surrounding the Pacific Ocean — about 90% of the world’s earthquakes occur there. The next most seismic region (5-6% of earthquakes) is the Alpide belt (extends from Mediterranean region, eastward through Turkey, Iran, and northern India.




     Active faults of the segmented Wasatch fault zone are next to the largest and growing population centers of central Utah.

    Active faults of the segmented Wasatch fault zone are next to the largest and growing population centers of central Utah. Structural fault segment boundaries play an unknown role in limiting large earthquakes (USGS).


    The Wasatch Range, with its outstanding ski areas, runs North-South through Utah, and like all mountain ranges it was produced by a series of earthquakes. The 386 km (240-mile)-long Wasatch Fault is made up of several segments, each capable of producing up to a M7.5 earthquake. During the past 6,000 years, there has been a M6.5+ about once every 350 years, and it has been about 350 years since the last powerful earthquake, which was on the Nephi segment.

    Earthquakes also occur in concentrated areas in the central portion of the United States. Some very powerful earthquakes occurred along the New Madrid fault in the Mississippi Valley in 1811-1812. Because of the crustal structure in the Central US which efficiently propagates seismic energy, shaking from earthquakes in this part of the country are felt at a much greater distance from the epicenters than similar size quakes in the Western US.

    The world’s deadliest recorded earthquake occurred in 1556 in central China. It struck a region where most people lived in caves carved from soft rock. These dwellings collapsed during the earthquake, killing an estimated 830,000 people. In 1976 another deadly earthquake struck in Tangshan, China, where more than 250,000 people were killed.

    Depth of Earthquakes

    Plate boundaries have a bearing on the depth of earthquakes. A majority of earthquakes globally are shallow earthquakes. The deepest earthquakes typically occur at plate boundaries where the Earth”s crust is being subducted into the Earth’s mantle. These occur as deep as 750 km (400 miles) below the surface.





    San Andreas Fault

    horizontal colored lines highlight different layers of sediment in exposure of the San Andreas fault in a trench

    Exposure of the San Andreas Fault in a trench. The horizontal colored lines highlight different layers of sediment. The red line is traced on a fault that offsets the layers. (Public domain.)

     yellow map of California showing San Andreas Fault and offset of Pinnacles

    Pinnacles, California Offset by San Andreas Fault. The present-day location of The Pinnacles is 195 mi (314 km) from the volcano that the San Andreas sliced it from. We know these volcanic rocks are 23 million years old. That means the San Andreas fault has moved 0.59 in/yr (1.5 cm/yr) over the last 23 million years. (USGS).


    The present-day location of The Pinnacles is 195 mi (314 km) northwest from the volcano that the San Andreas sliced it from. We know these volcanic rocks are 23 million years old. That means the San Andreas fault has moved 0.59 in/yr (1.5 cm/yr) over the last 23 million years. 

    Tsunami Facts

    • Tsunamis are triggered by earthquakes, volcanic eruptions, submarine landslides, and by onshore landslides in which large volumes of debris fall into the water. All of these triggers can occur in the United States.

    • If a tsunami-causing disturbance occurs close to the coastline, a resulting tsunami can reach coastal communities within minutes.

    • Although many people think of a tsunami as a single, breaking wave, it typically consists of multiple waves that rush ashore like a fast-rising tide with powerful currents. Tsunamis can travel much farther inland than normal waves.

    Life of a Tsunami


    Earthquakes are commonly associated with ground shaking that is a result of elastic waves traveling through the solid earth. As an earthquake or disturbance occurs at the ocean floor, the rebound generates a wave of water.

    Illustration shows a cross-section of a coastline and the beginnings of a tsunami wave that is caused by an earthquake.

    Note: In this figure, the waves are greatly exaggerated compared to water depth. In the open ocean, the waves are at most several meters high spread over many tens to hundreds of kilometers in length (USGS).

    During submarine earthquakes, when the seafloor is uplifted and rebounds, the entire water column may be pushed up and down. The potential energy that results from pushing water above mean sea level is then transferred to horizontal propagation of the tsunami wave (kinetic energy). For the case shown above, the earthquake rupture occurred at the base of the continental slope in relatively deep water. Situations can also arise where the earthquake rupture occurs beneath the continental shelf in much shallower water.

    2. SPLIT

    Illustration shows a cross-section of a coastline and how a tsunami wave changes through time.

    Within several minutes of the earthquake, the initial tsunami (Panel 1) is split into a tsunami that travels out to the deep ocean (distant tsunami) and another tsunami that travels towards the nearby coast (local tsunami). The height above mean sea level of the two oppositely traveling tsunamis is approximately half that of the original tsunami (Panel 1). (This is somewhat modified in three dimensions, but the same idea holds.) The speed at which both tsunamis travel varies as the square root of the water depth. Therefore, the deep-ocean tsunami travels faster than the local tsunami near shore.





    Illustration shows a cross-section of a coastline and how a tsunami wave changes through time.

    Several things happen as the local tsunami travels over the continental slope and approaches shallow water. The amplitude increases and the wavelength decreases resulting in steepening of the leading wave — an important control of wave runup at the coast (next panel). 

    Note that the first part of the wave reaching the local shore is a trough, which will appear as the sea recedes far from shore. This is a common natural warning sign for tsunamis. Note also that the deep ocean tsunami has traveled much farther than the local tsunami because of the higher propagation speed. As the deep ocean tsunami approaches a distant shore and shallowing waters, amplification and shortening of the wave will occur, just as with the local tsunami shown.

    4. RUNUP

    Tsunami runup occurs when a peak in the tsunami wave travels from the near-shore region onto shore. Runup is a measurement of the height of the water onshore observed above a reference sea level.

    Illustration shows a cross-section of a coastline and how a tsunami wave changes through time.

    Except for the largest tsunamis, such as the 2004 Indian Ocean event, most tsunamis do not result in giant breaking waves (like normal surf waves at the beach that curl over as they approach shore). Rather, they come in much like very strong and fast-moving tides (i.e., strong surges and rapid changes in sea level). Much of the damage inflicted by tsunamis is caused by strong currents and floating debris. The small number of tsunamis that do break often form vertical walls of turbulent water called bores. Tsunamis will often travel much farther inland than normal waves.

    Do tsunamis stop once on land? No! After runup, part of the tsunami energy is reflected back to the open ocean and scattered by sharp variations in the coastline. In addition, a tsunami can generate a particular type of coastal trapped wave called edge waves that travel back-and forth, parallel to shore. These effects result in many arrivals of the tsunami at a particular point on the coast rather than a single wave as suggested by Panel 3. Because of the complicated behavior of tsunami waves near the coast, the first runup of a tsunami is often not the largest, emphasizing the importance of not returning to a beach many hours after a tsunami first hits.

    This information is from USGS Fact Sheet 2006-3023 (February 2006)



     A Real Risk for the United States

    The 2004 Indian Ocean tsunami reached heights of 65 to 100 feet in Sumatra, caused more than 200,000 deaths from Indonesia to East Africa, and registered on tide gauges throughout the world. This tsunami killed more than 200,000 people in 11 countries around the Indian Ocean, the United States was reminded of its own tsunami risks.

    In fact, devastating tsunamis have struck North America before and are sure to strike again.

    Especially vulnerable are the five Pacific States — Hawaii, Alaska, Washington, Oregon, and California — and the U.S. Caribbean islands.

    In the wake of the Indian Ocean disaster, the United States is redoubling its efforts to assess the Nation's tsunami hazards, provide tsunami education, and improve its system for tsunami warning.

    The U.S. Geological Survey (USGS) is helping to meet these needs, in partnership with the National Oceanic and Atmospheric Administration (NOAA) and with coastal States and counties.

    The west coast of the U.S. has experienced tsunami impacts in the past (USGS)


    This map shows seven earthquake-generated tsunami events in the United States from the years 900 to 1964. The earthquakes that caused these tsunamis are: Prince William Sound, Alaska, 1964, magnitude 9.2; The Alaska tsunami led to 110 deaths, some as far away as Crescent City, Calif.

     Chile, 1960, magnitude 9.5; Alaska, 1946, magnitude 7.3-7.5; Puerto Rico/Mona Rift, 1918, an earthquake and tsunami killed 118 people in Puerto Rico. Several such events have struck this region in historic times.

    Virgin Islands, 1867, magnitude undetermined; Cascadia, 1700, magnitude 9; and Puget Sound, 900, magnitude 7.5. This tsunami that originated along the Washington, Oregon, and California coasts in 1700 overran Native American fishing camps and caused damage in Japan.


    Mass wasting is a general term for movement of rock, sediment or soils downslope under the force of gravity. This movement is started once the mass overcomes the force of friction, depending on factors such as rock type, amount of moisture, slope and strength. The most common type of mass wasting is a landslide.

    Landslide Types and Processes


    Landslides occur in the United States in all 50 States, but primarily they occur (and have the highest potential) at coastal and mountainous areas of California, Oregon, and Washington, the States comprising the intermountain west, and the mountainous and hilly regions of the Eastern United States. Alaska and Hawaii also experience all types of landslides.

    Landslides in the United States cause approximately $3.5 billion (year 2001 dollars) in damage, and kill between 25 and 50 people annually. Casualties in the United States are primarily caused by rockfalls, rock slides, and debris flows. Worldwide, landslides occur and cause thousands of casualties and billions in monetary losses annually.

    La Conchita, coastal area of southern California. This landslide and earthflow occurred in the spring of 1995. People were evacuated and the houses nearest the slide were completely destroyed. This is a typical type of landslide. Photo by R.L. Schuster, U.S. Geological Survey.


    An idealized slump-earth flow showing commonly used nomenclature for labeling the parts of a landslide (USGS)



    The term "landslide" describes a wide variety of processes that result in the downward and outward movement of slope-forming materials including rock, soil, artificial fill, or a combination of these. The materials may move by falling, toppling, sliding, spreading, or flowing. The various types of landslides can be differentiated by the kinds of material involved and the mode of movement. 




    A classification system based on these parameters is shown in figure 2. Other classification systems incorporate additional variables, such as the rate of movement and the water, air, or ice content of the landslide material.


    Figure 2. Table

    Figure 2. Types of landslides. Abbreviated version of Varnes' classification of slope movements (Varnes, 1978).


    Although landslides are primarily associated with mountainous regions, they can also occur in areas of generally low relief. In low-relief areas, landslides occur as cut-and-fill failures (roadway and building excavations), river bluff failures, lateral spreading landslides, collapse of mine-waste piles (especially coal), and a wide variety of slope failures associated with quarries and open-pit mines. The most common types of landslides are described as follows and are illustrated in figure 3.

    Figure 3. These schematics illustrate the major types of landslide movement 





    SLIDES: Although many types of mass movements are included in the general term "landslide," the more restrictive use of the term refers only to mass movements, where there is a distinct zone of weakness that separates the slide material from more stable underlying material. 

    The two major types of slides are 

    Rotational slide: This is a slide in which the surface of rupture is curved concavely upward and the slide movement is roughly rotational about an axis that is parallel to the ground surface and transverse across the slide (fig. 3A). 

    Translational slide: In this type of slide, the landslide mass moves along a roughly planar surface with little rotation or backward tilting (fig. 3B). A block slide is a translational slide in which the moving mass consists of a single unit or a few closely related units that move downslope as a relatively coherent mass (fig. 3C).

    FALLS: Falls are abrupt movements of masses of geologic materials, such as rocks and boulders, that become detached from steep slopes or cliffs (fig. 3D). Separation occurs along discontinuities such as fractures, joints, and bedding planes, and movement occurs by free-fall, bouncing, and rolling. Falls are strongly influenced by gravity, mechanical weathering, and the presence of interstitial water.

    TOPPLES: Toppling failures are distinguished by the forward rotation of a unit or units about some pivotal point, below or low in the unit, under the actions of gravity and forces exerted by adjacent units or by fluids in cracks (fig. 3E).

    FLOWS: There are five basic categories of flows that differ from one another in fundamental ways.

    a. Debris flow: A debris flow is a form of rapid mass movement in which a combination of loose soil, rock, organic matter, air, and water mobilize as a slurry that flows downslope (fig. 3F). Debris flows include <50% fines. Debris flows are commonly caused by intense surface-water flow, due to heavy precipitation or rapid snowmelt, that erodes and mobilizes loose soil or rock on steep slopes. Debris flows also commonly mobilize from other types of landslides that occur on steep slopes, are nearly saturated, and consist of a large proportion of silt- and sand-sized material. Debris-flow source areas are often associated with steep gullies, and debris-flow deposits are usually indicated by the presence of debris fans at the mouths of gullies. Fires that denude slopes of vegetation intensify the susceptibility of slopes to debris flows.

    b. Debris avalanche: This is a variety of very rapid to extremely rapid debris flow (fig. 3G).

    c. Earthflow: Earthflows have a characteristic "hourglass" shape (fig. 3H). The slope material liquefies and runs out, forming a bowl or depression at the head. The flow itself is elongate and usually occurs in fine-grained materials or clay-bearing rocks on moderate slopes and under saturated conditions. However, dry flows of granular material are also possible.

    d. Mudflow: A mudflow is an earthflow consisting of material that is wet enough to flow rapidly and that contains at least 50 percent sand-, silt-, and clay-sized particles. In some instances, for example in many newspaper reports, mudflows and debris flows are commonly referred to as "mudslides."

    e. Creep: Creep is the imperceptibly slow, steady, downward movement of slope-forming soil or rock. Movement is caused by shear stress sufficient to produce permanent deformation, but too small to produce shear failure. There are generally three types of creep: (1) seasonal, where movement is within the depth of soil affected by seasonal changes in soil moisture and soil temperature; (2) continuous, where shear stress continuously exceeds the strength of the material; and (3) progressive, where slopes are reaching the point of failure as other types of mass movements. Creep is indicated by curved tree trunks, bent fences or retaining walls, tilted poles or fences, and small soil ripples or ridges (fig. 3I).

    LATERAL SPREADS: Lateral spreads are distinctive because they usually occur on very gentle slopes or flat terrain (fig. 3J). The dominant mode of movement is lateral extension accompanied by shear or tensile fractures. 

    The failure is caused by liquefaction, the process whereby saturated, loose, cohesionless sediments (usually sands and silts) are transformed from a solid into a liquefied state. Failure is usually triggered by rapid ground motion, such as that experienced during an earthquake, but can also be artificially induced. When coherent material, either bedrock or soil, rests on materials that liquefy, the upper units may undergo fracturing and extension and may then subside, translate, rotate, disintegrate, or liquefy and flow. Lateral spreading in fine-grained materials on shallow slopes is usually progressive. The failure starts suddenly in a small area and spreads rapidly. Often the initial failure is a slump, but in some materials movement occurs for no apparent reason. Combination of two or more of the above types is known as a complex landslide.


    1. Geological causes

    a. Weak or sensitive materials

    b. Weathered materials

    c. Sheared, jointed, or fissured materials

    d. Adversely oriented discontinuity (bedding, schistosity, fault, unconformity, contact, and so forth)

    e. Contrast in permeability and/or stiffness of materials

    2. Morphological causes

    a. Tectonic or volcanic uplift

    b. Glacial rebound

    c. Fluvial, wave, or glacial erosion of slope toe or lateral margins

    d. Subterranean erosion (solution, piping)

    e. Deposition loading slope or its crest

    f. Vegetation removal (by fire, drought)

    g. Thawing

    h. Freeze-and-thaw weathering

    i. Shrink-and-swell weathering

    3. Human causes

    a. Excavation of slope or its toe

    b. Loading of slope or its crest

    c. Drawdown (of reservoirs)

    d. Deforestation

    e. Irrigation

    f. Mining

    g. Artificial vibration

    h. Water leakage from utilities


    Although there are multiple types of causes of landslides, the three that cause most of the damaging landslides around the world are these:

    Landslides and Water

    Slope saturation by water is a primary cause of landslides. This effect can occur in the form of intense rainfall, snowmelt, changes in ground-water levels, and water-level changes along coastlines, earth dams, and the banks of lakes, reservoirs, canals, and rivers.

    Landsliding and flooding are closely allied because both are related to precipitation, runoff, and the saturation of ground by water. In addition, debris flows and mudflows usually occur in small, steep stream channels and often are mistaken for floods; in fact, these two events often occur simultaneously in the same area.

    Landslides can cause flooding by forming landslide dams that block valleys and stream channels, allowing large amounts of water to back up. This causes backwater flooding and, if the dam fails, subsequent downstream flooding. Also, solid landslide debris can "bulk" or add volume and density to otherwise normal streamflow or cause channel blockages and diversions creating flood conditions or localized erosion. Landslides can also cause overtopping of reservoirs and/or reduced capacity of reservoirs to store water.

    Landslides and Seismic Activity

    Many mountainous areas that are vulnerable to landslides have also experienced at least moderate rates of earthquake occurrence in recorded times. The occurrence of earthquakes in steep landslide-prone areas greatly increases the likelihood that landslides will occur, due to ground shaking alone or shaking-caused dilation of soil materials, which allows rapid infiltration of water. The 1964 Great Alaska Earthquake caused widespread landsliding and other ground failure, which caused most of the monetary loss due to the earthquake. Other areas of the United States, such as California and the Puget Sound region in Washington, have experienced slides, lateral spreading, and other types of ground failure due to moderate to large earthquakes. Widespread rockfalls also are caused by loosening of rocks as a result of ground shaking. Worldwide, landslides caused by earthquakes kill people and damage structures at higher rates than in the United States.

    Landslides and Volcanic Activity

    Landslides due to volcanic activity are some of the most devastating types. Volcanic lava may melt snow at a rapid rate, causing a deluge of rock, soil, ash, and water that accelerates rapidly on the steep slopes of volcanoes, devastating anything in its path. These volcanic debris flows known as lahars of ash and mud reach great distances, once they leave the flanks of the volcano, and can damage structures in flat areas surrounding the volcanoes. The 1980 eruption of Mount St. Helens, in Washington triggered a massive landslide on the north flank of the volcano, the largest landslide in recorded times.

    Landslide Mitigation—How to Reduce the Effects of Landslides

    Vulnerability to landslide hazards is a function of location, type of human activity, use, and frequency of landslide events. The effects of landslides on people and structures can be lessened by total avoidance of landslide hazard areas or by restricting, prohibiting, or imposing conditions on hazard-zone activity. Local governments can reduce landslide effects through land-use policies and regulations. Individuals can reduce their exposure to hazards by educating themselves on the past hazard history of a site and by making inquiries to planning and engineering departments of local governments. They can also obtain the professional services of an engineering geologist, a geotechnical engineer, or a civil engineer, who can properly evaluate the hazard potential of a site, built or unbuilt.

    The hazard from landslides can be reduced by avoiding construction on steep slopes and existing landslides, or by stabilizing the slopes. Stability increases when ground water is prevented from rising in the landslide mass by (1) covering the landslide with an impermeable membrane, (2) directing surface water away from the landslide, (3) draining ground water away from the landslide, and (4) minimizing surface irrigation. Slope stability is also increased when a retaining structure and/or the weight of a soil/rock berm are placed at the toe of the landslide or when mass is removed from the top of the slope.

    8 NATURAL DISASTERS WATER RESOURCES Flooding, Drought, Pollution

    Flooding, Drought, Pollution


    Our water resources are currently monitored by many agencies. 


    The USGS works with partners to monitor, assess, conduct targeted research, and deliver information on a wide range of water resources and conditions including streamflow, groundwater, water quality, and water use and availability.


    The USEPA and other federal agencies face a number of challenges in ensuring that the nation has access to safe and clean water. Under the Safe Drinking Water Act (SDWA), EPA establishes legally enforceable standards that limit the levels of specific contaminants in drinking water.


    An agency within the Department of the Interior, the National Park Service, manages nearly 400 natural, cultural and recreational sites around the country. Part of the USDA, the NRCS helps private land owners conserve their soil, water, and other natural resources.


    The U.S. Army Corps of Engineers (USACE) Institute for Water Resources (IWR) was established to provide forward-looking analysis, cutting-edge methodologies, and innovative tools to aid USACE’s Civil Works program. IWR strives to improve the performance of the USACE water resources program through analysis of emerging water resources trends and issues; development, distribution, and training in the use of state-of-the-art methods and models in the areas of planning, operations, and civil engineering; and national data management of results-oriented program and project information across Civil Works business lines. In addition to implementing this vision throughout core mission areas, IWR oversees seven Centers that provide targeted technical expertise and support.




    Our water resources are widely protected and monitored. The following links are provided to explore the many agencies involved in water resources:







    Before understanding the many areas of environmental geology that encompass water, we must first understand the water cycle and how water moves through the earth.


    The water cycle describes where water is on Earth and how it moves. Human water use, land use, and climate change all impact the water cycle. By understanding these impacts, we can work toward using water sustainably. 

    What is the water cycle? 

    Earth, the water planet

    Credit: NASA

    Viewed from space, the most striking feature of our planet is the water. In both liquid and frozen form, it covers 75% of the Earth's surface. It fills the sky with clouds. Water is practically everywhere on Earth, from inside the planet's rocky crust to inside the cells of the human body (NASA). What's important to keep in mind is that all of this water is in constant motion across our planet.

    The water cycle describes where water is on Earth and how it moves. Water is stored in the atmosphere, on the land surface, and below the ground. It can be a liquid, a solid, or a gas. Liquid water can be fresh or saline (salty). Water moves between the places it is stored. Water moves at large scales, through watersheds, the atmosphere, and below the Earth's surface. Water moves at very small scales too. It is in us, plants, and other organisms. Human activities impact the water cycle, affecting where water is stored, how it moves, and how clean it is.


    Pools store water 

    96% of all water on Earth is in the ocean as saline. The remaining 4% of water on Earth is fresh water. 

    Fresh water is stored in liquid form in:

    Surface Water-Fresh water lakes, Artificial reservoirs, Rivers and Wetlands

    Groundwater-underground liquid water is stored in aquifers. Water in groundwater aquifers is found within cracks and pores in the rock. 

    Ice -Water is stored in solid, frozen form in ice sheets, glaciers, snowpack either at the poles or at high elevation

    Water vapor-Water in gaseous form stored as atmospheric moisture over the ocean and land.

    Soil-In the soil, frozen water is stored as permafrost and liquid water is stored as soil moisture.  

    As it moves, water can change form between liquid, solid, and gas. Circulation mixes water in the oceans and transports water vapor in the atmosphere. Water moves between the atmosphere and the surface through evaporation, evapotranspiration, condensation and precipitation. Water moves across the surface through snowmelt, runoff, and streamflow. Water moves into the ground through infiltration and groundwater recharge. Underground, groundwater flows within aquifers. Groundwater can return to the surface through natural discharge into rivers, the ocean, and from springs. 

    Conceição é uma freguesia portuguesa do município da Ribeira Grande showing fresh water and water vapor. (Photo Amey)

    What drives the water cycle? 

    Water moves naturally and because of human actions. Energy from the sun and the force of gravity drive the continual movement of water between pools. The sun’s energy causes liquid water to evaporate into water vapor. 

    Evapotranspiration is the main way water moves into the atmosphere from the land surface and oceans. Gravity causes water to flow downward on land. It causes rain, snow, and hail to fall from clouds.  



    Humans alter the water cycle 

    In addition to natural processes, the anthropogenic force on water greatly affects where water is stored and how water moves. We redirect rivers. We build dams to store water. We drain water from wetlands for development. We use water from rivers, lakes, reservoirs, and groundwater aquifers. We use that water to supply our homes and communities. We use it for agricultural irrigation and grazing livestock. We use it in industrial activities like thermoelectric power generation, mining, and aquaculture. 

    We also affect water quality. In agricultural and urban areas, irrigation and precipitation wash fertilizers and pesticides into rivers and groundwater. Power plants and factories return heated and contaminated water to rivers. Runoff carries chemicals, sediment, and sewage into rivers and lakes. Downstream from these sources, contaminated water can cause harmful algal blooms, spread diseases, and harm habitats for wildlife. 


    The water cycle and climate change 

    Climate change is an important impact on the water cycle in water quantity and timing. Climate change is discussed in more detail in Chapter 13. Precipitation patterns are changing. The frequency, intensity, and length of extreme weather events, like floods or droughts, are also changing. Ocean sea levels are rising, leading to coastal flooding. Climate change is also impacting water quality. It is causing ocean acidification which damages the shells and skeletons of many marine organisms. Climate change increases the likelihood and intensity of wildfires, which introduces unwanted pollutants from soot and ash into nearby lakes and streams. 



    What determines water availability? 

    Humans and other organisms rely on water for life. The amount of water that is available depends on how much water there is in each pool (water quantity). Water availability also depends on when and how fast water moves (water timing) through the water cycle. Finally, water availability depends on how clean the water is (water quality). By understanding human impacts on the water cycle, we can work toward using water sustainably.  

    The USGS monitors daily surface water levels on local basis with stream guages and has data on water resources across the US.





    What is flooding?

    According to The National Oceanic and Atmospheric Administration (NOAA), flooding is an overflowing of water onto land that is normally dry. Floods can happen during heavy rains, when ocean waves come on shore, when snow melts quickly, or when dams or levees break. Damaging flooding may happen with only a few inches of water, or it may cover a house to the rooftop. Floods can occur within minutes or over a long period, and may last days, weeks, or longer. Floods are the most common and widespread of all weather-related natural disasters.

    Flash floods are the most dangerous kind of floods, because they combine the destructive power of a flood with incredible speed. Flash floods occur when heavy rainfall exceeds the ability of the ground to absorb it. They also occur when water fills normally dry creeks or streams or enough water accumulates for streams to overtop their banks, causing rapid rises of water in a short amount of time. They can happen within minutes of the causative rainfall, limiting the time available to warn and protect the public.

    Where and when do floods occur?

    Flooding occurs in every U.S. state and territory, and is a threat experienced anywhere in the world that receives rain. In the U.S. floods kill more people each year than tornadoes, hurricanes or lightning.

    What areas are at risk from flash floods?

    Densely populated areas are at a high risk for flash floods. The construction of buildings, highways, driveways, and parking lots increases runoff by reducing the amount of rain absorbed by the ground. This runoff increases the flash flood potential.


    Sometimes, streams through cities and towns are routed underground into storm drains. During heavy rain, the storm drains can become overwhelmed or plugged by debris and flood the roads and buildings nearby. Low spots, such as underpasses, underground parking garages, basements, and low water crossings can become death traps.


    Areas near rivers are at risk from floods. Embankments, known as levees, are often built along rivers and are used to prevent high water from flooding bordering land. In 1993, many levees failed along the Mississippi River, resulting in devastating floods. The city of New Orleans experienced massive devastating flooding days after Hurricane Katrina came onshore in 2005 due to the failure of levees designed to protect the city.


    Dam failures can send a sudden destructive surge of water downstream. In 1889 a dam break upstream from Johnstown, Pennsylvania, released a 30-40 foot wall of water that killed 2200 people within minutes.


    Mountains and steep hills produce rapid runoff, which causes streams to rise quickly. Rocks and shallow, clayey soils do not allow much water to infiltrate into the ground. Saturated soils can also lead to rapid flash flooding. Camping or recreating along streams or rivers can be a risk if there are thunderstorms in the area. A creek only 6 inches deep in mountainous areas can swell to a 10-foot deep raging river in less than an hour if a thunderstorm lingers over an area for an extended period of time. Sometimes the thunderstorms that produce the heavy rainfall may happen well upstream from the impacted area, making it harder to recognize a dangerous situation.


    Very intense rainfall can produce flooding even on dry soil. In the West, most canyons, small streams and dry arroyos are not easily recognizable as a source of danger. The causative rainfall can occur upstream of the canyon, and hikers can be trapped by rapidly rising water. Floodwaters can carry fast-moving debris that pose significant risks to life.


    Additional high-risk locations include recent burn areas in mountains, and urban areas from pavement and roofs which enhance runoff.


    Ice jams and snowmelt can help cause flash floods. A deep snowpack increases runoff produced by melting snow. Heavy spring rains falling on melting snowpack can produce flash flooding. Melting snowpack may also contribute to floods produced by ice jams on creeks and rivers. Thick layers of ice often form on streams and rivers during the winter. Melting snow and/or warm rain running into the streams may lift and break this ice, allowing large chunks of ice to jam against bridges or other structures. This causes the water to rapidly rise behind the ice jam. If the water is suddenly released, serious flash flooding could occur downstream. Huge chunks of ice can be pushed onto the shore and through houses and buildings.

    Turn around, don’t drown! Most fatalities in the US from flash flooding are from vehicles driving into flooded roadways.

    NOAA and USGS monitor flooding on a large and local scale across the United States in real time. 






    The Federal Emergency Management Agency (FEMA) employs more than 20,000 people nationwide. Headquartered in Washington, D.C., we have 10 regional offices located across the country. We leverage a tremendous capacity to coordinate within the federal government to make sure America is equipped to prepare for and respond to disasters.

    FEMA’s mission is helping people before, during and after disasters, and our core values and goals help us achieve it.

    According to FEMA, A general and temporary condition of partial or complete inundation of 2 or more acres of normally dry land area or of 2 or more properties (at least 1 of which is the policyholder's property) from:

    1. Overflow of inland or tidal waters; or

    2. Unusual and rapid accumulation or runoff of surface waters from any source; or

    3. Mudslides (i.e., mudflows) which are proximately caused by flooding and are akin to a river of liquid and flowing mud on the surfaces of normally dry land areas, as when earth is carried by a current of water and deposited along the path of the current.; or

    4. Collapse or subsidence of land along the shore of a lake or similar body of water as a result of erosion or undermining caused by waves or currents of water exceeding anticipated cyclical levels that result in a flood as defined above.

    A flood inundates a floodplain. 

    Most floods fall into three major categories: riverine flooding, coastal flooding, and shallow flooding. Alluvial fan flooding is another type of flooding more common in the mountainous western states.



    A drought is a period of drier-than-normal conditions that results in water-related problems. When rainfall is less than normal for several weeks, months, or years, the flow of streams and rivers declines, water levels in lakes and reservoirs fall, and the depth to water in wells increases. If dry weather persists and water-supply problems develop, the dry period can become a drought. Add to natural means, the impacts are intensified with increased agricultural usage such as irrigation and rerouting to simple overuse in areas of very low rainfall.

    The term "drought" can have different meanings to different people, depending on how a water deficiency affects them. Droughts have been classified into different types such as:

    • meteorological drought - lack of precipitation

    • agricultural drought - lack of soil moisture, or

    • hydrologic drought -reduced streamflow or groundwater levels

    It is not unusual for a given period of water deficiency to represent a more severe drought of one type than another type. For example, a prolonged dry period during the summer may substantially lower the yield of crops due to a shortage of soil moisture in the plant root zone but have little effect on groundwater storage replenished the previous spring.

    The USGS closely monitors the effects of drought through data collection and research, and is studying the current drought in the context of long-term hydrologic, climatic, and environmental changes. These studies support successful planning and science-based decision-making by water managers who must address complex issues and competing interests in times of drought. They also and help decision-makers prepare for climate change and possible future drought.

    What are the impacts of drought?


    During times of drought, vegetation is visibly dry, stream and river flows decline, water levels in lakes and reservoirs fall, and the depth to water in wells increases. As drought persists, longer-term impacts can emerge, such as land subsidence, seawater intrusion, and damage to ecosystems. Unlike the immediate impacts of drought, however, long-term impacts can be harder to see, but more costly to manage in the future.

    Short-Term Drought Impacts

    During drought, declines in surface water are seen that are often devastating to water supplies for agriculture and cities, hydropower production, navigation, recreation, and habitat for aquatic and riparian species. 

    For example, several California Water Science Center streamgages have recently recorded streamflows that are below all-time record lows for specific days of the year. Annual runoff, which is calculated from this streamflow data, supplies many of our needs for water, and recent runoff estimates for California show measurements on par with 1930's and late 1970's droughts.

    Unlike the effects of a drought on streamflows, groundwater levels in wells may not reflect a shortage of rainfall for a year or more after a drought begins. Despite reduced availability, reliance upon groundwater often increases during drought throughincreased groundwater pumping to meet water demands. If water is pumped at a faster rate than an aquifer is recharged by precipitation or other sources, water levels can drop, resulting in decreased water availability and deterioration of groundwater quality.

    Ultimately, the surface water and groundwater form one interconnected hydrologic system. Nearly all surface water features - streams, lakes, reservoirs, wetlands, and estuaries - interact with groundwater. In addition to being a major source of water to lakes and wetlands, groundwater plays a crucial role in sustaining streamflow between precipitation events - especially during protracted dry periods. Although the contribution of groundwater to total streamflow varies widely among streams, hydrologists estimate the average contribution is somewhere between 40 and 50 percent.





    The USEPA supports efforts under the Clean Water Act and Safe Drinking Water Act. Water pollution and water quality has become a large field of study for the environmental geologist.  Hydrologists that study surface water and hydrogeologists are needed for When the water in our rivers, lakes, and oceans becomes polluted; it can endanger wildlife, make our drinking water unsafe, and threaten the waters where we swim and fish. 


    The USEPA has turned over the implementation of drinking water and watershed protection to the states. There needs to be an understanding of general water basics.


    United States enjoys one of the world's most reliable and safest supplies of drinking water. Congress passed the Safe Drinking Water Act (SDWA) in 1974 to protect public health, including by regulating public water systems. 


    The Safe Drinking Water Act (SDWA) requires EPA to establish and enforce standards that public drinking water systems must follow. EPA delegates primary enforcement responsibility (also called primacy) for public water systems to states and Indian Tribes if they meet certain requirements.


    Approximately 150,000 public water systems provide drinking water to most Americans. Customers that are served by a public water system can contact their local water supplier and ask for information on contaminants in their drinking water, and are encouraged to request a copy of their Consumer Confidence Report. This report lists the levels of contaminants that have been detected in the water, including those by EPA, and whether the system meets state and EPA drinking water standards.


    About 10 percent of people in the United States rely on water from private wells. Private wells are not regulated under the SDWA, typically the health department may oversee private wells.


    What is a Watershed?

    A watershed – the land area that drains to one stream, lake or river – affects the water quality in the water body that it surrounds. Like water bodies (e.g., lakes, rivers, and streams), individual watersheds share similarities but also differ in many ways. Every inch of the United States is part of a watershed – in other words, all land drains into a lake, river, stream or other water body and directly affects its quality. Because we all live on the land, we all live in a watershed — thus watershed condition is important to everyone.


    Watersheds exist at different geographic scales, too. The Mississippi River has a huge watershed that covers all or parts of 33 states. You might live in that watershed, but at the same time you live in a watershed of a smaller, local stream or river that flows eventually into the Mississippi. EPA’s healthy watersheds activities mainly focus on these smaller watersheds.(USEPA)


    This map shows one set of watershed boundaries in the continental United States; these are known as National hydrologic units (watersheds) (USGS)

    What is a Healthy Watershed?

    A healthy watershed is one in which natural land cover supports:

    • dynamic hydrologic and geomorphologic processes within their natural range of variation

    • habitat of sufficient size and connectivity to support native aquatic and riparian species

    • physical and chemical water quality conditions able to support healthy biological communities.

    • Natural vegetative cover in the landscape, including the riparian zone, helps maintain the natural flow regime and fluctuations in water levels in lakes and wetlands. A stream’s flow regime refers to its characteristic pattern of flow magnitude, timing, frequency, duration, and rate of change. The flow regime plays a central role in shaping aquatic ecosystems and the health of biological communities. Alteration of natural flow regimes (e.g., more frequent floods) can reduce the quantity and quality of aquatic habitat, degrade aquatic life, and result in the loss of ecosystem services.

    This, in turn, helps maintain natural geomorphic processes, such as sediment storage and deposition, that form the basis of aquatic habitats. Connectivity of aquatic and riparian habitats in the longitudinal, lateral, vertical, and temporal dimensions helps ensure the flow of chemical and physical materials and movement of biota among habitats.


    A healthy watershed has the structure and function in place to support healthy aquatic ecosystems. 


    Key components of a healthy watershed include:

    intact and functioning headwater streams


    riparian corridors

    biotic refugia

    instream habitat

    biotic communities

    natural vegetation in the landscape


    sediment transport

    fluvial geomorphology

    disturbance regimes expected for its location.


    Are Healthy Watersheds Very Common?

    Unfortunately not. Healthy watersheds are uncommon, particularly in the eastern U.S. as well as in most other parts of the nation that are urbanized, farmed, or mined. Large tracts of protected wildlands, mostly in the western U.S., are where most healthy watersheds can be found. However, some healthy watersheds exist in many regions of the country where water pollution has been prevented or well controlled, and where communities maintain the benefits of their clean waterways.


    How Might Healthy Watersheds Affect Me?

    You may potentially benefit from healthy watersheds in numerous ways, generally unseen and unrecognized by the average citizen: Healthy watersheds are necessary for virtually any high quality outdoor recreation sites involving the use of lakes, rivers, or streams. Great fishing opportunities are usually due to healthy watersheds that surround the waters that people love to fish.


    Your drinking water, if it comes from a surface water source, might be substantially less expensive to treat, if a healthy watershed around the water source filters pollution for free.

    Your property values may be higher, if you are fortunate enough to reside near healthy rather than impaired waters.


    You and your community’s quality of life may be better in these and other ways due to healthy watersheds; now, imagine how unhealthy watersheds might affect you as well.


    Why Do Watersheds Need to Be Protected?

    Healthy watersheds not only affect water quality in a good way, but also provide greater benefits to the communities of people and wildlife that live there.


    A watershed – the land area that drains to a stream, lake or river – affects the water quality in the water body that it surrounds. Healthy watersheds not only help protect water quality, but also provide greater benefits than degraded watersheds to the people and wildlife that live there. We all live in a watershed, and watershed condition is important to everyone and everything that uses and needs water. 


    Healthy watersheds provide critical services, such as clean drinking water, productive fisheries, and outdoor recreation, that support our economies, environment and quality of life. The health of clean waters is heavily influenced by the condition of their surrounding watersheds, mainly because pollutants can wash off from the land to the water and cause substantial harm. 


    Streams, lakes, rivers and other waters are interconnected with the landscape and all its activities through their watersheds. They are influenced by naturally varying lake levels, water movement to and from groundwater, and amount of stream flow. Other factors, such as forest fires, stormwater runoff patterns, and the location and amount of pollution sources, also influence the health of our waters.


    These dynamics between the land and the water largely determine the health of our waterways and the types of aquatic life found in a particular area. Effective protection of aquatic ecosystems recognizes their connectivity with each other and with their surrounding watersheds. Unfortunately, human activities have greatly altered many waters and their watersheds.

    Why is EPA Concerned with Healthy Watersheds?

    One of EPA’s most important jobs is to work with states and others to achieve the Clean Water Act’s primary goal – restore and maintain the integrity of the nation’s waters. Despite this law’s many pollution control successes, tens of thousands of streams, rivers and lakes have been reported as still impaired. The great majority of these involve pollution sources in their watersheds – the land area that surrounds and drains into these waters. Knowing the conditions in watersheds is crucial for restoring areas with degraded water quality, as well as protecting healthy waters from emerging problems before expensive damages occur.


    Achieving the Clean Water Act’s main goal depends on having good information about watersheds – their environmental conditions, possible pollution sources, and factors that may influence restoration and protection of water quality. EPA is investing in developing scientifically sound and consistent data sources, and making this information public and easily accessible to the wide variety of our partners working toward clean and healthy waters. 


    What is Being Done to Protect Healthy Watersheds?

    A very wide range of activities could be called healthy watersheds protection. These may include regulatory and non-regulatory approaches. EPA’s healthy watersheds protection activities are nonregulatory. Approaches used at state and local level could be either. The private sector is also actively involved in many forms of protection. 


    After decades of focusing almost exclusively on restoring impaired waters, EPA created the Healthy Watersheds Program (HWP) to bring more emphasis to proactively protecting high quality waters, following the Clean Water Act (CWA)'s objective “…to restore and maintain the chemical, physical, and biological integrity of the Nation’s waters.” The HWP takes a non-regulatory, collaborative approach to maintaining clean waters by supporting EPA and its partners in their efforts to identify, assess and protect watershed health through Clean Water Act programs. 

    This approach is essential for addressing future threats such as:

    emerging water quality problems,

    loss and fragmentation of aquatic habitat,

    altered water flow and availability,

    invasive species, and

    climate change.


    How is a Healthy Watershed Identified?

    There are literally hundreds of watershed characteristics (such as environmental traits, sources of degradation, and community factors) that may influence environmental health and quality of life, for better or worse. Identifying and comparing these characteristics is known as watershed assessment. This process is the main way to compare watershed condition across large areas such as states, and find the healthy watersheds among the rest.


    What is Evaluated in a Healthy Watersheds Assessment?

    EPA’s process for assessing healthy watersheds looks at small scale watersheds – either catchments (which average about one square mile in area) or HUC12 watersheds (which average about 35 square miles in area). The factors for describing and comparing watersheds, called indicators, are selected specifically for the area of the country being studied. Although custom selections of indicators are made to suit the study area, all assessments develop a comparative index of watershed health and index of watershed vulnerability. These complementary indices help states and other users find out where the healthiest watersheds are, and also what their level of vulnerability might be.


    How Much Healthy Watersheds Assessment has been Done in the U.S.?

    Several states have developed statewide assessments of their healthy watersheds on their own over the past decade. EPA has partnered with states and watershed groups in several additional locales to generate more statewide watershed assessments. However, in many states, there are still no completed studies to identify the healthy watersheds or their vulnerabilities. EPA is currently working to provide these states with preliminary healthy watersheds assessments.

    Research, Monitoring and Assessment


    NOAA’s Mussel Watch Program monitors the level of chemicals in oysters, mussels and sediments.

    NOAA’s Mussel Watch Program monitors the level of chemicals in oysters, mussels, and sediments.

    Because nonpoint source pollution poses many threats to environmental and human health, scientists are working hard to effectively manage this problem. Research, monitoring and assessments of the environment are increasing their knowledge of the causes and effects of nonpoint source pollution, and leading to the development of strategies to reduce and control it.


    Computer modeling is one technique that scientists are using to better understand how nonpoint source pollution affects waterbodies. A model, or simulation, is a computer program that allows scientists to predict how an environmental "system" like a river, lake, or coastal waterbody may change as a result of varying physical or chemical conditions. Models can also predict the progression and severity of such conditions. With this knowledge, scientists can develop techniques to prevent harmful environmental conditions before they occur.

    To develop models, scientists may concentrate on variables that are the most obvious indicators of nonpoint source pollution and potential eutrophication. For example: In a waterbody, nitrate-nitrogen levels above 1 part per million (ppm) and total phosphorus levels above 0.1 ppm can contribute to increased plant growth and eutrophication. Similarly, levels of dissolved oxygen below 1 or 2 ppm may indicate a that a waterbody is experiencing eutrophic conditions. At these low levels of oxygen, aquatic organisms may be starved for oxygen and die.

    Scientists will create a model that simulates these conditions, and can then forecast the potential effects of eutrophication, as well as where it might occur.


    Research and the use of models provides scientists with important information that they can use to develop long-term monitoring programs. The data gathered from these monitoring efforts is then used to improve the accuracy of the original models.

    NOAA's Mussel Watch Project is one example of a monitoring program. It is designed to watch the levels of chemicals in oysters, mussels, and sediments. The project aims to predict trends in pollution across the country and determine which areas are at the greatest risk for contamination. Samples of mussels and oysters are collected every two years, and sediments are sampled once a decade to test for chemical contamination.

    Collecting and analyzing river sediment data across the country

    Scientists at NOAA, and other agencies, such as the U.S. Geological Survey (USGS) and the U.S. Environmental Protection Agency, sample sediments through various long-term monitoring programs. One program, the USGS National Water Quality Assessment program, has been collecting and analyzing river sediment data across the country since 1991. Scientists test for nutrients and pesticides that are used in nearby agricultural, urban and suburban areas.

    The U.S. Geological Survey's National Water Quality Assessment (NAWQA) program is another example of a long-term monitoring project. Since 1991, NAWQA has been collecting and analyzing data at river basins and aquifers (layers of rock or soil that contain large amounts of water) across the country. Scientists monitor for nutrients (nitrogen, phosphorus, etc.) and pesticides that are frequently used in agricultural operations and suburban areas.

    NOAA's National Estuarine Eutrophication Survey compiled data gathered from 138 estuaries in the United States. The data revealed that more than 90 percent of U.S. estuaries exhibited eutrophic symptoms. More than half of the estuaries exhibited moderate to high levels of at least one eutrophic symptom, such as low oxygen levels, loss of submerged aquatic vegetation (SAV), or the presence of harmful algal blooms (HABs). Estuaries along the Gulf of Mexico and the Mid-Atlantic Coast showed the highest levels of eutrophic symptoms. These areas suffer the most intense agricultural use and urban runoff.


    Research using computer models combined with long-term monitoring allows scientists to assess conditions, determine the relationships between nonpoint source pollution and its impacts, and recommend standards and strategies to control pollution.

    Assessments are used to help plan control strategies. In 1998, the U.S. Environmental Protection Agency (EPA) published the National Strategy for the Development of Regional Nutrient Criteria. The strategy is an effort to develop specific criteria for nutrient levels in waterbodies, which will help states implement sound water quality standards.

    Other control strategies include state coastal nonpoint pollution control programs, which are mandated under the Coastal Zone Act Reauthorization Amendments (CZARA) of 1990. The CZARA requires coastal states and territories to develop and implement specific pollution control programs.


    Research, Monitoring and Assessment

    NOAA’s Mussel Watch Program monitors the level of chemicals in oysters, mussels and sediments.

    NOAA’s Mussel Watch Program monitors the level of chemicals in oysters, mussels, and sediments.

    Because nonpoint source pollution poses many threats to environmental and human health, scientists are working hard to effectively manage this problem. Research, monitoring and assessments of the environment are increasing their knowledge of the causes and effects of nonpoint source pollution, and leading to the development of strategies to reduce and control it.


    Computer modeling is one technique that scientists are using to better understand how nonpoint source pollution affects waterbodies. A model, or simulation, is a computer program that allows scientists to predict how an environmental "system" like a river, lake, or coastal waterbody may change as a result of varying physical or chemical conditions. Models can also predict the progression and severity of such conditions. With this knowledge, scientists can develop techniques to prevent harmful environmental conditions before they occur.

    To develop models, scientists may concentrate on variables that are the most obvious indicators of nonpoint source pollution and potential eutrophication. For example: In a waterbody, nitrate-nitrogen levels above 1 part per million (ppm) and total phosphorus levels above 0.1 ppm can contribute to increased plant growth and eutrophication. Similarly, levels of dissolved oxygen below 1 or 2 ppm may indicate a that a waterbody is experiencing eutrophic conditions. At these low levels of oxygen, aquatic organisms may be starved for oxygen and die.

    Scientists will create a model that simulates these conditions, and can then forecast the potential effects of eutrophication, as well as where it might occur.


    Research and the use of models provides scientists with important information that they can use to develop long-term monitoring programs. The data gathered from these monitoring efforts is then used to improve the accuracy of the original models.

    NOAA's Mussel Watch Project is one example of a monitoring program. It is designed to watch the levels of chemicals in oysters, mussels, and sediments. The project aims to predict trends in pollution across the country and determine which areas are at the greatest risk for contamination. Samples of mussels and oysters are collected every two years, and sediments are sampled once a decade to test for chemical contamination.

    Collecting and analyzing river sediment data across the country

    Scientists at NOAA, and other agencies, such as the U.S. Geological Survey (USGS) and the U.S. Environmental Protection Agency, sample sediments through various long-term monitoring programs. One program, the USGS National Water Quality Assessment program, has been collecting and analyzing river sediment data across the country since 1991. Scientists test for nutrients and pesticides that are used in nearby agricultural, urban and suburban areas.

    The U.S. Geological Survey's National Water Quality Assessment (NAWQA) program is another example of a long-term monitoring project. Since 1991, NAWQA has been collecting and analyzing data at river basins and aquifers (layers of rock or soil that contain large amounts of water) across the country. Scientists monitor for nutrients (nitrogen, phosphorus, etc.) and pesticides that are frequently used in agricultural operations and suburban areas.

    NOAA's National Estuarine Eutrophication Survey compiled data gathered from 138 estuaries in the United States. The data revealed that more than 90 percent of U.S. estuaries exhibited eutrophic symptoms. More than half of the estuaries exhibited moderate to high levels of at least one eutrophic symptom, such as low oxygen levels, loss of submerged aquatic vegetation (SAV), or the presence of harmful algal blooms (HABs). Estuaries along the Gulf of Mexico and the Mid-Atlantic Coast showed the highest levels of eutrophic symptoms. These areas suffer the most intense agricultural use and urban runoff.


    Research using computer models combined with long-term monitoring allows scientists to assess conditions, determine the relationships between nonpoint source pollution and its impacts, and recommend standards and strategies to control pollution.

    Assessments are used to help plan control strategies. In 1998, the U.S. Environmental Protection Agency (EPA) published the National Strategy for the Development of Regional Nutrient Criteria. The strategy is an effort to develop specific criteria for nutrient levels in waterbodies, which will help states implement sound water quality standards.

    Other control strategies include state coastal nonpoint pollution control programs, which are mandated under the Coastal Zone Act Reauthorization Amendments (CZARA) of 1990. The CZARA requires coastal states and territories to develop and implement specific pollution control programs.


    Groundwater Quality 

    Groundwater: Child about to get water from a groundwater well.

    Groundwater usually looks crystal clear, but before drinking it, care must be taken to make sure it doesn't contain dissolved chemicals that could be harmful (USGS)

    Just because you have a well that yields plenty of water doesn't mean you can go ahead and just take a drink. Because water is such an excellent solvent it can contain lots of dissolved chemicals. And since groundwater moves through rocks and subsurface soil, it has a lot of opportunity to dissolve substances as it moves. For that reason, groundwater will often have more dissolved substances than surface water will.

    Even though the ground is an excellent mechanism for filtering out particulate matter, such as leaves, soil, and bugs, dissolved chemicals and gases can still occur in large enough concentrations in groundwater to cause problems. Underground water can get contaminated from industrial, domestic, and agricultural chemicals from the surface. This includes chemicals such as pesticides and herbicides that many homeowners apply to their lawns.

    Contamination of groundwater by road salt is of major concern in northern areas of the United States. Salt is spread on roads to melt ice, and, with salt being so soluble in water, excess sodium and chloride is easily transported into the subsurface groundwater. The most common water-quality problem in rural water supplies is bacterial contamination from septic tanks, which are often used in rural areas that don't have a sewage-treatment system. Effluent (overflow and leakage) from a septic tank can percolate (seep) down to the water table and maybe into a homeowner's own well. Just as with urban water supplies, chlorination may be necessary to kill the dangerous bacteria.




    Diagram showing groundwater contamination from a waste disposal site.

    The U.S. Geological Survey (USGS) is involved in monitoring the Nation's groundwater supplies. A national network of observation wells exists to measure regularly the water levels in wells and to investigate water quality.

    Contaminants can be natural or human-induced

    Naturally occurring contaminants are present in the rocks and sediments. As groundwater flows through sediments, metals such as iron and manganese are dissolved and may later be found in high concentrations in the water. Industrial discharges, urban activities, agriculture, groundwater pumpage, and disposal of waste all can affect groundwater quality. Contaminants from leaking fuel tanks or fuel or toxic chemical spills may enter the groundwater and contaminate the aquifer. Pesticides and fertilizers applied to lawns and crops can accumulate and migrate to the water table.


    Map of the U.S. showing areas of high risk for nitrogen contamination of groundwater.


    One USGS model, based on nationwide data, was developed to estimate the risk of nitrate contamination to shallow ground water across the United States. The model integrates nitrogen inputs and aquifer vulnerability by use of Geographic Information System (GIS) technology. Nitrogen inputs include commercial fertilizer and manure application rates, atmospheric contributions, and population densities (the latter representing residential and urban nitrogen sources, such as septic systems, fertilizers, and domestic animal waste). Aquifer vulnerability is represented by soil-drainage characteristics—the ease with which water and chemicals can seep to ground water—and the extent to which woodlands are interspersed with cropland.

    Groundwater can contain hydrogen sulfide or other naturally occurring chemicals. Groundwater also may contain petroleum, organic compounds, or other chemicals introduced by humans' activities. Contaminated groundwater can occur if the well is located near land that is used for farming where certain kinds of chemicals are applied to crops, or near a gas station that has a leaking storage tank. Leakage from septic tanks and/or waste-disposal sites also can contaminate groundwater. A septic tank can introduce bacteria to the water, and pesticides and fertilizers that seep into farmed soil can eventually end up in water drawn from a well. Or, a well might have been placed in land that was once used for something like a garbage or chemical dump site. In any case, it is wise to have your well water tested for contaminates.

    The physical properties of an aquifer, such as thickness, rock or sediment type, and location, play a large part in determining whether contaminants from the land surface will reach the groundwater. The risk of contamination is greater for unconfined (water-table) aquifers than for confined aquifers because they usually are nearer to land surface and lack an overlying confining layer to impede the movement of contaminants. Because groundwater moves slowly in the subsurface and many contaminants sorb to the sediments, restoration of a contaminated aquifer is difficult and may require years, decades, centuries, or even millennia.

    Many Americans drink groundwater from their own wells

    If you drive on a rural highway almost anywhere in the Nation you might see some small "doghouse-looking" enclosures or some metal pipes and tubing in the side yard of many homes and trailer parks. These are small wells that supply water to individual and small groups of families.

    If you ask them if the possible contamination of groundwater is of interest to them, they would have to say "yes". This is the case with tens of millions of people across the country.







    The map below shows the percentage of each State's population that relies on their own well water for home use. Percentages range from 1 percent in Puerto Rico to 44 percent in Maine, with the National average being 14 percent. You can view this and other maps and the corresponding data from the USGS publication "Estimated Use of Water in the United States, 2015".

    Map of U.S., by state, showing percentage of state's population using self-supplied water

    USGS publication "Estimated Use of Water in the United States, 2015".






    Photo: Amey

    Coastal erosion is the process by which local sea level rise, strong wave action, and coastal flooding wear down or carry away rocks, soils, and/or sands along the coast. All coastlines are affected by storms and other natural events that cause erosion; the combination of storm surge at high tide with additional effects from strong waves—conditions commonly associated with landfalling tropical storms—creates the most damaging conditions. The extent and severity of the problem is worsening with global sea level rise, but it differs in different parts of the country, so there is no one-size-fits-all solution.

    Beach Erosion from a Storm in New York

    A November nor'easter caused severe beach erosion and damage on Long Island's South Shore.

    In the United States, coastal erosion is responsible for roughly $500 million per year in coastal property loss, including damage to structures and loss of land. To mitigate coastal erosion, the federal government spends an average of $150 million every year on beach nourishment and other shoreline erosion control measures.1 In addition to beach erosion, more than 80,000 acres of coastal wetlands are lost annually—the equivalent of seven football fields disappearing every hour of every day.2 The aggregate result is that the United States lost an area of wetlands larger than the state of Rhode Island between 1998 and 2009.3

    House on top of a crumbling cliff above ocean waves

    Cliff erosion is a common storm-induced hazard along the West Coast.

    While coastal erosion affects all regions of the United States, erosion rates and potential impacts are highly localized. Average coastline recession rates of 25 feet per year are not uncommon on some barrier islands in the Southeast, and rates of 50 feet per year have occurred along the Great Lakes. Severe storms can remove wide beaches, along with substantial dunes, in a single event. In undeveloped areas, these high recession rates are not likely to cause significant concern, but in heavily populated locations, one or two feet of coastal erosion may be considered catastrophic.

    Sea level rise will cause an increase in coastal erosion and the human response will be critical. If we choose to build hard structures in an attempt to keep the shoreline position stable, we will lose beach area due to scour. If we let the shoreline migrate naturally, we can expect to see erosion rates increase, especially in regions of the coast that are already dealing with starved sediment budgets and rapid shoreline migration. Increases in storm frequency and intensity in the future will also cause increased coastal erosion.


    Coastal Landforms

    Rocky Coast Landforms

    A wave crashes into the rocks at Ship Harbor.A wave crashes into the rocks at Ship Harbor in Acadia National Park, Maine.(NPS)

    The pounding surf and breaking waves found on rocky coasts have inspired ocean lovers for generations. Erosion characterizes these high-energy environments, which are typically located on active margins with narrow continental shelves (on account of subduction). Rocky coasts may be composed of any rock type (i.e., sedimentary, igneous, or metamorphic) and are usually the site of complex tectonic landforms such as faults, folds, and igneous intrusions and extrusions. Bedrock composition, climate, and wave patterns dictate the profile of rocky coasts. Resistant bedrock combined with high-energy wind and wave activity will create a steep profile, whereas easily erodible rocks in low-energy environments will create a more gradual profile, for example, the high cliffs of Kalaupapa National Historical Park (Hawaii) versus the gently sloping rocky coastline of Dry Tortugas National Park (Florida). In addition, glacial activity may produce steep, rocky coasts through the production of fjords and talus slopes. Carbonate coasts, dominated by skeletal and shelly materials, may form eolianite dunes—calcium carbonate beach dune deposits that are lithified and may be eroded to form steep cliffs and bluffs.

    Geologic Features of Rocky Coasts

    Rocky coastlines have many spectacular features. Waves cut arches and sea stacks that jut into the water. Bluffs, cliffs, and terraces form as rock is eroded. Fjords are made when glacial valleys are filled with water when sea level rises.


    Between 1.8 million to 10,000 years ago, Pleistocene glaciers carved steep valleys that were eventually drowned by rising sea levels. The inundated valleys created by glacier movement are called fjords. Kenai Fjords National Park in Alaska provides excellent examples of rocky coasts along fjords. 

    Headlands, Pocket Beaches, and Wave Refraction

    Headlands and pocket beaches of Channel Islands National Park in California are distinctively shown in aerial photographs. Waves are refracted around the headlands, increasing erosion at seaward positions on the islands in the park. The protected embayments, where wave action is subdued between headlands, are often transformed into sandy pocket beaches. In lower-energy pocket beaches, sediment transport is not able to carry sediment downshore except during increased wave, wind, and storm activity. Pocket beaches may be ephemeral and change seasonally, or even disappear, on account of increased energy events.

    Sea Caves

    The headlands on rocky coasts are exposed to intense wave, wind, and storm action. Eventually sea caves may form in less resistant, easily erodible bedrock located on promontories. These caves are distinctive environments that are particularly suited for bryozoans, sponges, barnacles, tubeworms, and some species of shade-tolerant red algae. Sea caves are popular with recreational boaters and divers. 

    Sea Arches and Sea Stacks

    The constant erosion of rocky headlands may produce a variety of particular geomorphic structures, including sea arches and sea stacks. These isolated remnants of the headland have been detached from the mainland. With prolonged erosion, sea arches may collapse to form sea stacks—steep pillars of rock a short distance from the mainland. Both sea stacks and sea arches are impermanent features that will eventually disappear with continued erosion. Hundreds of these beautiful features have been observed along the coastline of Olympic National Park, Washington.

    Sea Cliffs

    The shape and appearance of sea cliffs depends on the stratigraphy, geologic structures, angle of deposition, and lithology of the bedrock material in which the cliffs are formed. Massive rocks, such as granite, will normally erode in a uniform manner, whereas layered sedimentary rocks may erode in a step-wise fashion. Because of increased wave activity found in the midlatitudes, numerous steep cliff slopes exist there, as compared to the high and low latitudes. Na Pali—“sea cliffs”—rise thousands of feet above the peninsula and ocean within Kalaupapa National Historical Park in Hawaii. Recognized as a significant remaining example of sea cliffs in our nation’s natural heritage, this area was designated as the North Shore Cliffs National Natural Landmark in 1972.

    Tidewater Glaciers

    Tidewater or tidal glaciers terminate at the sea or within a fjord. These glaciers are some of the best-studied glaciers because of easy access to their termini or snouts. Depending on climate, topography, and amount of snowfall over time, tidewater glaciers may periodically experience rapid retreat, creating many large icebergs. If icebergs drift into nearby shipping lanes—especially those containing oil tankers, for example, in Alaska—such recession can be catastrophic. Tidewater glaciers are usually bright whitish-blue due to ice density and the tendency of calving (breaking into the sea). Glacier Bay National Park and Preserve in Alaska hosts many tidewater glaciers.




    Sandy Coast Landforms

    sandy beach with rippled pattern and dune grasses

    Windswept beach, Fire Island National Seashore, New York (2015).NPS Photo


    Sandy beaches are highly dynamic environments subject to rapid, extreme changes. Typically located on passive margins, in areas characterized by low-wave energy, a wide continental shelf, and high offshore sediment influence, sandy beaches are found in wave-dominated, depositional settings such as the Atlantic Ocean and Gulf of Mexico coasts. Many of our favorite beaches are found on sandy coasts: Cape Cod National Seashore in Massachusetts, Cumberland Island National Seashore in Georgia, Assateague Island National Seashore in Maryland and Virginia, Padre Island National Seashore in Texas, and Gulf Islands National Seashore in Florida and Mississippi.


    Sandy beaches may be found in other tectonic settings or depositional environments, such as pocket beaches at Channel Islands National Park and beaches near the mouth of San Francisco Bay at Golden Gate National Recreation Area in California.


    Depositional settings along sandy coasts produce barrier structures such as bay barriers, barrier spits, and barrier islands. Coastal barriers are highly complex and dynamic landforms that experience constant change and movement. These narrow strips of sand serve as obstacles to wave activity, protecting fragile environments that lay further inland, for example, marshes, tidal flats, and lagoons.

    Geologic Features of Sandy Coasts

    Depositional processes along coastlines, such as sediment transport, form sandy beaches and create highly complex landforms that experience constant change and movement. Features such as spits, barrier islands, tombolos, and dunes are classic forms in sandy beach environments.

    Barrier Islands

    Barrier islands are one of the most common and distinguishable features of the Atlantic coast. These important environments protect the mainland from storm events and wave action, while providing a vital ecosystem for many species. Features such as sand dunes, maritime forests, inlets, lagoons, back-barrier marshes, and vegetation constitute these fragile coastal systems. Without intervention, barrier islands maintain a state of dynamic equilibrium between sediment exchange, wave energy, and sea level rise. Human activities may interfere with this balance, causing costly damage, both economically and environmentally.

    Barrier Spits

    Barrier spits are made up of sediments that have been suspended by waves and transported by currents. A barrier spit is the landform resulting from the deposition of sediments in long ridges extending out from coasts. Barrier spits may partially block the mouths of bays. If a spit grows long enough, it can completely cut off a bay from the ocean, forming a lagoon. The spit is then called a bay barrier or a bay-mouth bar. Cape Cod (Massachusetts) is a famous cape that terminates at Provincetown spit.


    Although varying in length, width, sand composition, and permanence, beaches are the most well-known coastal feature. A beach is defined as the location along a shoreline where the sediment is in motion, being moved by waves, tides, and currents. The beach is often bounded on the upland side by a cliff, dune, or vegetation. Beaches are very dynamic environments, with coastlines that can change daily, making them challenging places to manage.


    Dunes are critical to the health and sustainability of sandy beaches. The primary dune ridge (foredunes) lies adjacent to the shoreline. Secondary dune fields may lie further inland. Dunes may form anywhere that eolian processes (wind transportation) occur. Dunes provide much-needed protection to back-barrier environments (including human development) against severe wave, wind, and storm events. In addition, these geomorphic features provide critical habitat to a variety of migratory birds and mammals. Dune vegetation is very important for the formation and stabilization of dune complexes on barrier islands. Both the root system and exposed vegetation restrict sand movement around plants, helping to build and secure the dune.


    A tombolo is created when sediment connects an offshore landform—such as an island or a sea stack—with the mainland. The tombolo forms because the island or sea stack refracts the waves, causing a zone of slow moving water behind the island. Whenever water carrying sediment slows down, sediment is deposited. The sediments that form tombolos often form in ridges along an underwater wave-cut terrace.

    Tropical Coast Landforms

    lagoon with patch reefs

    The same physical processes act on tropical coastlines—to produce either rocky headlands or long, flat sandy shorelines—as in other latitudes. However, in warm tropical waters, colonies of corals form, mostly between 30° north and 30° south latitude. Corals are animals, but they are stationary; their food source is washed to them through continuous water motions. Corals have an associated diverse array of reef fish, which attract snorkelers and scuba divers. As live corals grow atop the skeletons of dead corals, a coral reef is formed.

    Because living corals require a minimum sea temperature for growth, they are concentrated in the tropics, as are various calcareous algae that form carbonate encrustations along many tropical shores. They also favor clear waters (they cannot live in deltas or muddy environments) and, in general, depths shallower than 75 feet (23 m), although some species tolerate depths of up to 500 feet (152 m) (Wyckoff 1999).

    The most well-known type of reef is a barrier reef, which is built in shallow waters that may deepen through time. These reefs may reach enormous proportions. The Pacific island, Tahiti, is encircled by a barrier reef. The Great Barrier Reef of Australia (actually a composite of some 2,500 small reefs) is about 1,200 miles (1,931 km) long, with a lagoon tens of miles (kilometers) wide.

    Geologic Features of Tropical Coasts

    Reefs that are exposed above sea level are among the most massive and impressive landforms. Today, such reefs exist as huge, colonies; they also exist as “fossil” relics making up much of the world’s limestone. Among reef formations in the United States is the one that makes up Guadalupe Mountains and Carlsbad Caverns National Parks in Texas and New Mexico, respectively.

    Erosion of coastal landforms, especially cliffs, is not generally a significant source of sediment in the tropics where environments with low wave energies are common. This observation is supported by the relative lack of coasts formed of bedrock in the tropics. Even where present, cliffs formed of well-consolidated strata recede slowly and supply little sediment.

    Delta Landforms

    An aerial view of the Red River and mountains near the Lake Clark coastAn aerial view of the Red River and mountains near the coast Lake Clark National Park and Preserve, Alaska. (NPS Photo)

    Where rivers provide large quantities of sediment to the shore, estuaries are filled and river sediments are discharged directly into the ocean. If the rate of sediment supply exceeds the rate of sediment removal by waves and tidal currents, a buildup of sediment occurs at river mouths. These deposits, which commonly assume triangular shapes in planar view, are termed deltas because they resemble the Greek capital letter delta (Δ).

    In actuality, not all deltas display the classic “delta” form. This characteristic shape develops typically at river mouths, where waves and tides do not influence the amount of sediment supplied by the river. Such systems, exemplified by the Mississippi River delta, are called river-dominated deltas. Waves dominate riverine deposits in coastal areas where wave energy is high. Wave erosion and strong longshore currents disperse the sediment away from the river mouth, producing a relatively straight coast with only slight seaward bulges of the shoreline. In some regions, a large tidal range overshadows river and wave effects, creating tidal-dominated deltas. The strong flood and ebb tidal currents rearrange the river-supplied sediment into long, linear submarine ridges and islands that tend to fan out from the river mouth, creating funnel-shaped basin geometries.

    Estuary Landforms

    Landscape shot of hybrid cordgrass in San Francisco Bay salt marshes.

    San Francisco Bay salt marshes.

    The term “estuary” is derived from the Latin word “aestuarium,” which means tidal. In a geomorphic sense, a typical estuary is a semi-enclosed, elongated coastal basin that receives an inflow of both freshwater and saltwater. From a chemical and physical standpoint, estuaries are buffer zones between river (freshwater) and ocean (saltwater) environments that are affected by tidal oscillations.


    Geologically speaking, most estuaries are young basins, established by the flooding of fluvial (river-eroded) or glacially-scoured valleys during the Holocene rise of sea level. Estuaries are generally short-lived: they are quickly destroyed by rapid sediment infilling that is fostered by the high influx of river sediment. Circulation in estuaries not only traps large amounts of river sediment but also imports sand and mud from offshore areas.


    Not all semi-enclosed coastal bodies of water are estuaries. For example, lagoons are protected bodies of water that are little affected by tides. Lagoons may receive inputs of seawater and freshwater but are typically dominated by one or the other, making their water motions less complex than the mixing and circulation patterns associated with true estuaries.


    Lakeshore Landforms

    View of several small islands off the shore of Isle Royale National ParkView of several small islands off the shore of Isle Royale National Park, Michigan (NPS)

    The designated lakeshores in the national park system have shorelines and are, therefore, considered coastal and are managed accordingly. Nevertheless, because even the largest lakes are very small compared to oceans, some distinct differences exist, geomorphically speaking. Many lakeshores have much smaller waves and currents than occur in ocean basins. Furthermore, lakes are naturally short-lived: they tend to fill with sediments and to be emptied by streams downcutting their edges. Thus, some lake waves and currents have insufficient time for creating large landforms.

    Although astronomical lake tides (those caused by Moon–Sun gravitational attraction) are relatively insignificant, other movements of lake water can be substantial. In the event known as a seiche, wind pushes water up against one shore and the water then flows back to the opposite shore, like water in a washtub being rocked. Seiches can be important in the transportation of sediments. Investigators have measured seiches in Lake Erie up to 20 feet in height. 

    Waves on large bodies of water such as the Great Lakes shape shores of loose material, building sand barriers (including spits), as well as beaches with scarps, berms, and beach ridges. Storm waves can attack weak bedrock that fringes lakeshores, undercutting these rock formations and creating cliffs.

    Lakeshores also exhibit rill marks, swash marks, and ripple marks. On the landward side of beaches, enough sand may be deposited for dunes to form; for example, the spectacular Indiana Dunes at the southeastern edge of Lake Michigan formed of glacial drift.

    Littoral Caves

    The headlands on rocky lakeshores are exposed to intense wave, wind, and storm action. Eventually littoral caves may form in less resistant, easily erodible bedrock located on promontories.

    Coastal Erosion and Deposition

    Coastal processes create many erosional or depositional features we see when visiting the National Parks such as:

    • Beach Ridges
      Beach ridges are wave deposited sand ridges running parallel to shoreline.

    • Wave-Cut Scarps
      A wave-cut scarp is a steep bank created by wave erosion.

    • Marine Terraces
      A marine terrace is a raised beach or 'perched coastline' that has been raised out of the reach of wave activity.






    This simple diagram shows the factors that can affect coastal cliff erosion, including sea level rise, wave energy, coastal slope, beach width, beach height, and rock strength.

    Coastal Erosion at Drew Point, AlaskaThese photos show an area near Drew Point, along Alaska's northern coast. Taken on August 9, 2007, the photo on the left shows how ocean waves have undercut the land nearest the shore. Grassy turf extends out over a wave-cut notch. Taken on June 20, 2008, the photo on the right shows what often follows such undercutting: chunks of coastline tumbling into the sea. (USGS)

    Shoreline "hardening" 

    In the past, protecting the coast often meant "hardening" the shoreline with structures such as seawalls, groins, rip-rap, and levees. As understanding of natural shoreline function improves, there is a growing acceptance that structural solutions may cause more problems than they solve.4 Structural projects interfere with natural water currents and prevent sand from shifting along coastlines. Additional reasons to avoid structural protective measures include the high costs to install and maintain them, state or local prohibitions against them, their propensity to cause erosion to adjacent beaches and dunes, and the unintended diversion of stormwater and waves onto other properties.

    Infographic showing examples of living shoreline

    Beach nourishment

    Many states have shifted toward non-structural shoreline stabilization techniques. Unlike structural projects, nature-based or "green infrastructure" protection measures enhance the natural ability of shorelines to absorb and dissipate storm energy without interfering with natural coastal processes.5

    One common strategy for dealing with coastal erosion is beach nourishment—placing additional sand on a beach to serve as a buffer against erosion or to enhance the recreational value of the beach. However, beach nourishment has also become a controversial shore protection measure, in part because it has the potential to adversely impact a variety of natural resources. Consequently, these projects must comply with a wide range of complex laws and regulations. Beach nourishment is also expensive: check the Beach Nourishment Viewer to explore details about sand placement efforts for more than 2,000 beach nourishment projects since 1923. Adding sand to a beach does not guarantee that it will stay there. Some communities bring in huge volumes of sand repeatedly, only to see it wash out to sea in the next season's storms.

    Heavy equipment moving sand on a beach

    U.S. Army Corps of Engineers’ contractors pump sand dredged from the bottom of the Chesapeake Bay up to Norfolk, Virginia’s Ocean View Beach. The sand is part of a $34.5 million project to reduce storm damage risk to infrastructure along a 7.3 mile stretch of waterfront. When completed in 2017, the beach was 60 feet wide and sloped up to 5 feet above mean low water.


    Nonetheless, many communities still practice beach nourishment. The U.S. Army Corps of Engineers (USACE) is authorized to carry out beach nourishment for shoreline protection: their Beach Nourishment site describes the benefits of adding sand to beaches. USACE also offers a well illustrated booklet, How Beach Nourishment Projects Work.

    Recently, the U.S. Army Corps of Engineers has re-emphasized the need to consider a whole range of solutions to coastal erosion, not only structural solutions. For instance, non-structural shore protection methods that have the potential to control erosion include stabilizing dunes with fences and/or native vegetation, wetland protection and restoration, and relocation or removal of structures and debris. 

    Coastal restoration

    Even with the implementation of coastal shoreline erosion and risk reduction measures, residual risk remains. Some areas are constantly in danger during severe storms. For some regions of the country, the more intense storms are predicted to increase in strength and frequency as climate continues to change, though the overall frequency of all storms may decrease. In some cases, the only way to prevent structures from causing harm may be to remove them entirely. After the structure has been removed, communities usually dedicate the land to public open space or transfer it to land trusts for protection.

    Coastal restoration projects can be highly cost-effective for communities. Benefits of returning land to its undeveloped state include buffering storm surges, safeguarding coastal homes and businesses, sequestering carbon and other pollutants, creating nursery habitat for commercially and recreationally important fish species, and restoring open space and wildlife that support recreation, tourism, and the culture of coastal communities.

    Groins and Jetties

    groin structures along the coast

    Successive groin structures along the coast south of Gateway National Recreation Area, New Jersey. (National Park Service NPS)

    Groins are shore perpendicular structures, used to maintain updrift beaches or to restrict longshore sediment transport. By design, these structures are meant to capture sand transported by the longshore current; this depletes the sand supply to the beach area immediately down-drift of the structure. In response, down-drift property managers often install groins on adjacent properties to counteract the increased erosion, leading to a cascading effect of groin installation.

    Jetties are another type of shore perpendicular structure and are placed adjacent to tidal inlets and harbors to control inlet migration and minimize sediment deposition within the inlet. Similar to groins, jetties may significantly destabilize the coastal system and disrupt natural sediment regimes. 

    Jetties and groins can be constructed from a wide range of materials, including armorstone, precast concrete units or blocks, rock-filled timber cribs and gabions, steel sheet pile, timber sheet pile, and grout filled bags and tubes. Sea level rise increases the possibility of flanking or submergence of these structures. Landward retreat of the adjacent beach and dune line may leave the structure’s landward attachment point exposed. This increases the likelihood of additional maintenance costs and development of new features.

    Coastal Adaptation Strategies Handbook


    10 WASTE DISPOSAL Solid & Radioactive

    What is a Municipal Solid Waste Landfill?

    A municipal solid waste landfill (MSWLF) is a discrete area of land or excavation that receives household waste. A MSWLF may also receive other types of nonhazardous wastes, such as commercial solid waste, nonhazardous sludge, conditionally exempt small quantity generator waste, and industrial nonhazardous solid waste. 

    In 2009, there were approximately 1,908 MSWLFs in the continental United States all managed by the states where they are located.

    Non-hazardous solid waste is regulated under Subtitle D of RCRA. States play a lead role in ensuring the federal criteria for operating municipal solid waste and industrial waste landfills regulations are met, and they may set more stringent requirements. In absence of an approved state program, the federal requirements must be met by waste facilities. The revised criteria in Title 40 of the Code of Federal Regulations (CFR) part 258 addresses seven major aspects of MSWLFs, which include the following:

    • Location restrictions—ensure that landfills are built in suitable geological areas away from faults, wetlands, flood plains or other restricted areas.

    • Composite liners requirements—include a flexible membrane (i.e., geo-membrane) overlaying two feet of compacted clay soil lining the bottom and sides of the landfill. They are used to protect groundwater and the underlying soil from leachate releases.

    • Leachate collection and removal systems—sit on top of the composite liner and removes leachate from the landfill for treatment and disposal. Leachate is liquid formed when rain water filters through wastes placed in a landfill. When this liquid comes in contact with buried wastes, it leaches, or draws out, chemicals or constituents from those wastes.

    Operating practices—include compacting and covering waste frequently with several inches of soil. These practices help reduce odor, control litter, insects, and rodents, and protect public health.

    The image shows a cross-section of a municipal solid waste landfill. (USEPA)

    The environmental geologist will have to follow these requirements to monitor the landfill.



    Groundwater Monitoring Requirements


    Groundwater monitoring requirements—requires testing groundwater wells to determine whether waste materials have escaped from the landfill.


    Nearly all MSWLFs are required to monitor the underlying groundwater for contamination during their active life and post-closure care periods. The exceptions to this requirement are small landfills that receive less than 20 tons of solid waste per day, and facilities that can demonstrate that there is no potential for the migration of hazardous constituents from the unit into the groundwater. All other MSWLFs must comply with the groundwater monitoring requirements found at Title 40 of the Code of Federal Regulations (CFR) Part 258, Subpart E–Ground-Water Monitoring and Corrective Action.

    Facility owners and operators must install a groundwater monitoring system that can collect samples from the uppermost aquifer (i.e., defined as the geological formation nearest the natural surface that is capable of yielding significant quantities of groundwater to wells or springs) to monitor groundwater. The groundwater monitoring system consists of a series of wells placed up-gradient and down-gradient of the MSWLF. The samples from the up-gradient wells show the background concentrations of constituents in the groundwater, while the down-gradient wells show the extent of groundwater contamination caused by the MSWLF. The required number of wells, spacing and depth of wells is determined on a site-specific basis based on the aquifer thickness, groundwater flow rate and direction, and the other geologic and hydro-geologic characteristics of the site. All groundwater monitoring systems must be certified by a qualified groundwater scientist and must comply with the sampling and analytical procedures outlined in the regulations.

    Detention Monitoring

    MSWLF owner/operators monitor for the 62 constituents listed in Appendix I of 40 CFR Part 258 during the detection monitoring phase. This consists of sampling at least semiannually throughout the facility's active life and post-closure care period. The frequency of sampling is determined on a site-specific basis by the state regulatory agency.

    If one of the 62 constituents is detected at a statistically significant higher level than the established background level during the detection monitoring phase, the MSWLF owner/operators must notify the state regulatory agency. The facility must establish an assessment monitoring program within 90 days, unless the owner/operators can prove that the detection of the constituent(s) was the result one of the following reasons:

    • sampling, analysis, or statistical evaluation error (i.e., a false positive result);

    • a natural fluctuation in groundwater quality;

    • or caused by another source

    Assessment Monitoring

    A MSWLF must begin an assessment monitoring program within 90 days of detecting a statistically significant increase in the constituents listed in Appendix I constituents. Samples must be taken from all wells and analyzed for the presence of all 214 constituents listed in Appendix II of 40 CFR Part 258 as a first step. The owner/operators must then establish the background levels for these constituents and establish a groundwater protection standard (GWPS) for each if any of the constituents listed in Appendix II are detected.

    The GWPS represents the maximum allowable constituent level in the groundwater and is based either on the Safe Drinking Water Act (SDWA) Maximum Contaminant Level (MCL) for that constituent or the background level of the groundwater at the site if no MCL exists. The background level is used for the GWPS in cases where the site-specific background level is higher than the MCL.

    The owner/operators must resample for all previously detected constituents that are listed in Appendix I and Appendix II within 90 days of establishing the background levels and the GWPS. Resampling must then be repeated at least semiannually. The facility may return to the detection monitoring phase if none of the Appendix II constituents are found to exceed the GWPS for two consecutive sampling events. However, the owner/operators of the MSWLF must characterize the nature of the release, determine if the contamination has migrated beyond the facility boundary, and begin assessing corrective measures if any of the constituents are detected at a statistically significant level higher than the GWPS.

    • Corrective action provisions—control and clean up landfill releases and achieves groundwater protection standards.


    Corrective Action

    A remedy is selected and corrective action begins based upon the assessment of corrective measures. Any corrective measure selected must be protective of human health and the environment, meet the GWPS, control the source(s) of the release to prevent further releases, and manage any solid waste generated in accordance with all applicable RCRA regulations. The facility must continue these remedial actions until it has complied with the GWPS for three consecutive years and can demonstrate that all required actions have been completed.


    Closure and Post-Closure Care Requirements

    1997 Final Rule

    Revisions to Criteria for Municipal Solid Waste Landfills

    The closure and post-closure care requirements for MSWLFs establish the minimum requirements that MSWLF owner/operators must comply once the landfill stops receiving waste and begins closure. Owner/operators are also required to continue monitoring and maintaining the landfill once it is closed to protect against the release of hazardous constituents to the environment. The closure and post-closure care regulations can be found at 40 CFR Part 258, Subpart F - Closure and Post-Closure Care.


    Final Cover Systems

    The closure standards for MSWLFs require owner/operators to install a final cover system to minimize infiltration of liquids and soil erosion. The permeability of the final cover must be less than the underlying liner system, but no greater than 1.0 x 10-5 cm/sec. This requirement helps prevent the “bathtub effect” where liquids infiltrate through the overlying cover system but are contained by a more permeable underlying liner system. This causes the landfill to fill up with water (like a bathtub), increasing the hydraulic head on the liner system that can lead to the contaminated liquid (leachate) escaping and contaminating groundwater supplies.

    The final cover system must include an infiltration layer of at least 18 inches of earthen material covered by an erosion layer of at least 6 inches of earthen material that is capable of sustaining native plant growth. An alternative cover design may be used if it provides equivalent protection against infiltration and erosion. These alternative designs must be approved by the director of an approved and authorized state program.

    Closure Plans

    Every MSWLF is required to prepare a written closure plan that describes the steps necessary to close the unit in accordance with the closure requirements. This plan must include the following information:

    • A description of the final cover design and its installation methods and procedures

    • An estimate of the largest area of the landfill requiring a final cover

    • An estimate of the maximum inventory of waste on site during the landfill’s active life

    • A schedule for completing all required closure activities

    The MSWLF must begin closure operations within 30 days once a MSWLF has received its final shipment of waste. However, the MSWLF may delay closure for up to one year if additional capacity remains. Further delays following one year requires approval from the state director. All closure activities must be completed within 180 days (with the exception of an extension from the state director) after beginning. The owner/operators must then certify that the closure has been completed in accordance with the official closure plan after closure is complete. This certification must be signed by an independent, registered professional engineer or the state director. After this, the MSWLF owner/operators must also make a notation on the property deed indicating that the land was used as a landfill and that it is restricted from future use.

    Post-Closure Care

    Post-closure care activities consist of monitoring and maintaining the waste containment systems and monitoring groundwater to ensure that waste is not escaping and polluting the surrounding environment. The required post-closure care period is 30 years from site closure, but this can be shortened or extended by the director of an approved state program. That can help ensure protection of human health and the environment.

    Specific post-closure care requirements consist of maintaining the integrity and effectiveness of the following:

    • Final cover system

    • Leachate collection system

    • Groundwater monitoring system

    • Methane gas monitoring system

    The owner/operator of a closed MSWLF must prepare a written post-closure care plan that provides the following information:

    • A description of all required monitoring and maintenance activities, including the frequency with which each activity will be performed

    • The name, address and telephone number of the person to contact during the post-closure care period

    • A description of planned uses of the land during the post-closure care period

    Any use of the land during this period must not disturb the integrity or operation of any of the waste containment systems or the monitoring systems. The owner/operator must certify that the post-closure care has been completed in accordance with the official post-closure care plan following the post-closure care period. This certification must be signed by an independent, registered professional engineer or the state director. Once signed, the certification is placed in the facility’s operating record.

    Some materials may be banned from disposal in MSWLFs, including common household items like paints, cleaners/chemicals, motor oil, batteries and pesticides. Leftover portions of these products are called household hazardous waste. These products, if mishandled, can be dangerous to your health and the environment. Many MSWLFs have a household hazardous waste drop-off station for these materials.

    MSWLFs can also receive household appliances (i.e. white goods) that are no longer needed. Many of these appliances, such as refrigerators or window air conditioners, rely on ozone-depleting refrigerants and their substitutes. MSWLFs follow the federal disposal procedures for household appliances that use refrigerants. EPA has general information on how refrigerants can damage the ozone layer and consumer information on the specifics for disposing of these appliances.


    Municipal Solid Waste Transfer Stations


    Waste transfer stations are facilities where municipal solid waste (MSW) is unloaded from collection vehicles. The MSW is briefly held while it is reloaded onto larger long-distance transport vehicles (e.g. trains, trucks, barges) for shipment to landfills or other treatment or disposal facilities. Communities can save money on the labor and operating costs of transporting the waste to a distant disposal site by combining the loads of several individual waste collection trucks into a single shipment.

    They can also reduce the total number of trips traveling to and from the disposal site. Although waste transfer stations help reduce the impacts of trucks traveling to and from the disposal site, they can cause an increase in traffic in the immediate area where they are located. If not properly sited, designed and operated they can cause problems for residents living near them.

    Related Information

    In 1999, the National Environmental Justice Advisory Council undertook a study of the impacts that waste transfer stations have on poor and minority communities.

    A Regulatory Strategy for Siting and Operating Waste Transfer Stations provides information about waster transfer stations and the actions EPA has taken to address this issue.





    About Radioactive Waste

    As defined in the United States, there are five general categories of radioactive waste:

    • High-level waste: High-level waste includes used nuclear fuel from nuclear reactors and waste generated from the reprocessing of spent nuclear fuel. Although defense-related activities generate most of the United States’ liquid high-level waste, the majority of spent nuclear fuel is from commercial nuclear power plant reactors. Currently, most high-level waste is stored at the site where the waste was generated.

    • Transuranic waste: Transuranic wastes refer to man-made radioactive elements that have an atomic number of 92 (uranium) or higher. Most of the transuranic waste in the United States is from nuclear weapons production facilities. This waste includes common items such as rags, tools, and laboratory equipment contaminated during the early age of nuclear weapons research and development. Transuranic waste is currently being stored at several federal facilities across the country. Transuranic waste created as part of a defense program will ultimately be disposed of at the Waste Isolation Pilot Plant (WIPP) in New Mexico, which began accepting waste in 1999.

    • Uranium or thorium mill tailings: Mill tailings are radioactive wastes that remain after the mining and milling of uranium or thorium ore. Mill tailings are stored at the production-sites in specially designed ponds called impoundments.

    • Low-level waste: Low-level waste is radioactively contaminated industrial or research waste that is not high-level waste or uranium or thorium mill tailings. Much of this waste looks like common items such as paper, rags, plastic bags, protective clothing, cardboard, and packaging material. These items are considered waste once they come into contact with radioactive materials. Low-level waste can be generated by any industry using radioactive material, including government, utility, manufacture, medical and research facilities. There are disposal facilities that specialize in the near-surface disposal of low-level waste.

    • Technologically enhanced naturally-occurring radioactive material (TENORM): Some radiological material can exist naturally in the environment. In some cases, naturally-occurring radiological material (NORM) can become concentrated through human activity, such as mining or natural resource extraction. NORM that has been concentrated or relocated is known as Technologically Enhanced NORM, or TENORM. Many industries and processes can produce TENORM, including mining, oil and gas drilling and production and water treatment. TENORM wastes must be disposed or managed according to state regulations. Learn more about TENORM.

    Like all radioactive material, radioactive wastes will naturally decay over time. Once the radioactive material has decayed sufficiently, the waste is no longer hazardous. However, the time it will take for the radioactive material to decay will range from a few hours to hundreds of thousands of years. Some radioactive elements, such as plutonium, are highly radioactive and remain so for thousands of years. Learn more about radioactive decay

    What You Can Do

    • Be aware. It is highly unlikely that you would unknowingly encounter radioactive waste. However, if you are near a facility that manages radioactive waste, follow safety instructions.

    • Stay away. Keeping distance between you and radioactive waste will help keep you from being exposed. Never touch, inhale or ingest radioactive waste. Radioactive materials and other contaminants from waste can be very dangerous inside the body.

    Where to Learn More

    The U.S. Environmental Protection Agency (EPA)

    The EPA is responsible under the Atomic Energy Act for developing general environmental standards that apply to both the Department of Energy (DOE)-operated and the U.S. Nuclear Regulatory Commission (NRC)-licensed facilities that use radioactive material. Other statutes provide the EPA with authority to establish standards for specific wastes or facilities. These include the Nuclear Waste Policy Act, Waste Isolation Pilot Plant Land Withdrawal Act and the Energy Policy Act of 1992, that affect development and implementation standards for the management and disposal of waste at certain disposal facilities; the Uranium Mill Tailings Radiation Control Act (UMTRCA) that enables the EPA to set limits on radiation from mill tailings; and the Clean Air Act that limits radon emissions from mill tailing impoundments.

    The EPA has developed safety training for workers who could come into contact with radioactive material and radioactive wastes. Workers and managers in any of the industries that produce radioactive waste can take this training to learn more about recognizing and properly disposing of radioactive wastes.

    EPA’s Role at the Waste Isolation Pilot Plant (WIPP)

    This webpage provides information about the EPA’s role at the WIPP.

    Atomic Energy Act

    This webpage provides information on the Atomic Energy Act of 1946.

    Clean Air Act

    This webpage provides information on the Clean Air Act of 1970.

    Nuclear Waste Policy Act

    This webpage provides information on the Nuclear Waste Policy Act of 1982.

    Energy Policy Act

    This webpage provides information on the Energy Policy Act of 1992.

    EPA’s Role in Low-level Radioactive Waste

    This webpage provides information on “low-activity” radioactive waste and proposed rulemaking activities by the EPA.

    Uranium Mill Tailings Radiation Control Act (UMTRCA)

    This webpage provides more information about UMTRCA.

    The U.S. Nuclear Regulatory Commission (NRC)

    The NRC is responsible for licensing facilities and ensuring their compliance with the EPA standards. This includes having regulatory agreements to properly dispose of radioactive waste and setting performance objectives for disposal facilities that accept the waste. Many states have entered into formal agreements with the NRC to exercise authority over the licensing and operation of various activities that produce radioactive waste as well as low-level waste disposal facilities. These states are known as Agreement States.

    Should radioactive wastes need to be transported, the NRC in conjunction with the U.S. Department of Transportation (DOT) is responsible for regulating the transportation of wastes to storage and disposal sites.

    The NRC Agreement State Program

    This webpage provides information about the NRC Agreement State program and lists links to additional information.

    How the NRC Protects You

    This webpage provides information about how the NRC regulates and inspects sites where radioactive materials are used.

    Radioactive Waste Transportation

    This website provides information on how radioactive materials are shipped in the United States.

    The U.S. Department of Energy (DOE)

    The DOE is responsible for managing much of the nation’s radioactive wastes. These include providing a repository for high-level waste, including spent nuclear fuel; operating the WIPP, the facility that stores the nation’s defense-related transuranic radioactive waste; and providing a disposal option for the portion of the NRC-regulated low-level waste that is not generally suitable for near-surface disposal (known as “greater-than-Class C” low-level waste).

    The DOE also manages certain closed disposal sites, including those designated for uranium milling wastes.

    Nuclear Waste Storage

    This webpage provides information on how the DOE is working towards finding long-term storage solutions for nuclear waste.

    Off-site Source Recovery Program

    This webpage provides information on how the DOE‘s NNSA removes sealed radioactive sources that pose a potential risk to national security, health and safety.

    Greater-than-Class C (GTCC) Low-level Waste

    This webpage provides information on the DOE’s efforts to establish a disposal facility for Greater-than-Class C (GTCC) low-level waste.

    U.S. Department of Transportation (DOT)

    The DOT oversees the safety and security of hazardous materials during transport. DOT’s Office of Hazardous Materials Safety (OHMS) writes rules for shipping hazardous materials by highway, rail, air and sea. DOT works with the NRC to ensure that these materials are shipped safely. The NRC and the DOT are responsible for regulating the transportation of wastes to storage and disposal sites.

    Hazardous Material 

    This webpage provides information on hazardous material spills, including the types of hazardous material transported in the U.S. historic incident trends, and hazard classes.

    Transporting Radioactive Materials Fact Sheet

    This fact sheet provides information about transportation of radioactive waste in the United States including rules and guidance.

    The Conference of Radiation Control Program Directors (CRCPD)

    The CRCPD is a nonprofit non-governmental professional organization dedicated to radiation protection. 

    State Radiation Protection Programs

    This webpage provides links and contact information for each state's Radiation Control Program office.

    Source Collection and Threat Reduction (SCATR) Program

    Conference of Radiation Control Program Directors

    This webpage provides information about the CRCPD program that helps protect people from unnecessary exposure to radiation.


    11 WASTE DISPOSAL Hazardous, Injection, Incineration RCRA, CERCLA

    Resource Conservation and Recovery Act (RCRA) Overview

    Access the Statute and Amendments

    The United States Code (U.S.C.) is the codification by subject matter of the general and permanent laws of the United States.

    RCRA gives EPA the authority to control hazardous waste from the "cradle-to-grave." This includes the generation, transportation, treatment, storage and disposal of hazardous waste. To achieve this, EPA develops regulations, guidance and policies that ensure the safe management and cleanup of solid and hazardous waste, and programs that encourage source reduction and beneficial reuse.

    On this page:


    What is RCRA?

    What we commonly know as RCRA is actually a combination of the first federal solid waste statutes and all subsequent amendments. Learn more on our History of RCRA web page. These statutes and amendments describe the waste management program mandated by Congress that gave EPA authority to develop the RCRA program.

    Additionally, the term RCRA is often used interchangeably to refer to the statutes and amendments, the regulations and EPA policy and guidance. The difference is that EPA regulations carry out the congressional intent by providing explicit, legally enforceable requirements for waste management. These regulations can be found in title 40 of the Code of Federal Regulations (CFR), parts 239 through 282. EPA guidance documents and policy directives clarify issues related to the implementation of the regulations. Check out the RCRA Tools and Resources webpage to find RCRA guidance and policy directives.


    How does RCRA work?

    Opportunities for Public Participation

    The public plays a key role in RCRA by providing input and comments during almost every stage of the program’s development and implementation through rulemaking participation and comments on treatment, storage and disposal facility permits. Find more information on public participation.

    RCRA establishes the framework for a national system of solid waste control. Subtitle D of the Act is dedicated to non-hazardous solid waste requirements, and Subtitle C focuses on hazardous solid waste. Solid waste includes solids, liquids and gases and must be discarded to be considered waste.

    Congress has amended RCRA several times, which requires the President’s signature to become law. EPA translates this direction into operating programs by developing regulations, guidance and policy.

    States play the lead role in implementing non-hazardous waste programs under Subtitle D. EPA has developed regulations to set minimum national technical standards for how disposal facilities should be designed and operated. States issue permits to ensure compliance with EPA and state regulations.

    The regulated community is comprised of a large, diverse group that must understand and comply with RCRA regulations. These groups can include hazardous waste generators, government agencies and small businesses, and gas stations with underground petroleum tanks.

    Subtitle D – Non-hazardous Waste

    Enforcement and Compliance

    Non-hazardous solid waste is regulated under Subtitle D of RCRA. Regulations established under Subtitle D ban open dumping of waste and set minimum federal criteria for the operation of municipal waste and industrial waste landfills, including design criteria, location restrictions, financial assurance, corrective action (cleanup), and closure requirement. States play a lead role in implementing these regulations and may set more stringent requirements. In absence of an approved state program, the federal requirements must be met by waste facilities.

    Subtitle C – Hazardous Waste

    Hazardous waste is regulated under Subtitle C of RCRA. EPA has developed a comprehensive program to ensure that hazardous waste is managed safely from the moment it is generated to its final disposal (cradle-to-grave). Under Subtitle C, EPA may authorize states to implement key provisions of hazardous waste requirements in lieu of the federal government. If a state program does not exist, EPA directly implements the hazardous waste requirements in that state. Subtitle C regulations set criteria for hazardous waste generators, transporters, and treatment, storage and disposal facilities. This includes permitting requirements, enforcement and corrective action or cleanup.

    Other RCRA Provisions




    General Provisions


    Office of Solid Waste; Authorities of the Administrator and Interagency Coordinating Committee


    Duties of the Secretary of Commerce in Resource and Recovery


    Federal Responsibilities


    Miscellaneous Provisions


    Research, Development, Demonstration and Information


    Regulation of Underground Storage Tanks


    Standards for the Tracking And Management of Medical Waste


    RCRA Today

    RCRA Programs by the Numbers

    • Managing 2.96 billion tons of solid, industrial and hazardous waste.

    • Overseeing 6,600 facilities with over 20,000 process units in the full permitting universe.

    • Working to address more than 3,700 existing contaminated facilities needing cleanup, and reviewing as many as 2,000 possible facilities.

    • Providing $97.3 million in grant funding to help states implement authorized hazardous waste programs.

    • Providing incentives and opportunities to reduce or avoid greenhouse gas emissions through material and land management practices.

    EPA has largely focused on building the hazardous and municipal solid waste programs, and fostering a strong societal commitment to recycling and pollution prevention. Ensuring responsible waste management practices is a far-reaching and challenging task that engages EPA headquarters, regions, state agencies, tribes and local governments, as well as everyone who generates waste.

    It is important to look at the RCRA program’s nationwide accomplishments to understand where it is now and where it is headed in the future.

    • Developing a comprehensive system and federal/state infrastructure to manage hazardous waste from “cradle-to-grave.”

    • Establishing the framework for states to implement effective municipal solid waste and non-hazardous secondary material management programs.

    • Preventing contamination from adversely impacting our communities and resulting in future Superfund sites.

    • Restoring 18 million acres of contaminated lands, nearly equal to the size of South Carolina, and making the land ready for productive reuse through the RCRA Corrective Action program.

    • Creating partnership and award programs to encourage companies to modify manufacturing practices in which to generate less waste and reuse materials safely.

    • Enhancing perceptions of wastes as valuable commodities that can be part of new products through its sustainable materials management efforts.

    • Bolstering the nation’s recycling infrastructure and increasing the municipal solid waste (MSW) recycling/composting rate from less than seven percent to about 32.1 percent (as of 2018).

    ​The RCRA program has evolved in response to changes in waste generation and management aspects that could not have been foreseen when the program was first put in place. The RCRA program is needed to address continuing challenges, including the following:

    • Highly toxic waste.

    • Wastes from increasingly efficient air and water pollution control devices.

    • Population growth that places larger demands on our natural resources.

    • Long term stewardship of facilities that closed with waste in place.

    Looking towards the future, it is important for the RCRA program to continue to fulfill its mission by

    • Continuing to safeguard communities and the environment.

    • Mitigating and cleaning up contamination.

    • Championing sustainable, lifecycle waste and material management approaches.

    • Promoting economic development (including job creation) and community well being.

    • Embracing technological advances that will facilitate commerce and enhance stakeholders’ participation in the decisions affecting their communities.

    RCRA's critical mission supporting graphic image banner

    View the RCRA’s Critical Mission & the Path Forward to learn more about the critical role the RCRA program continues to play in protecting communities, restoring land and conserving resources across the nation.



    Superfund: CERCLA Overview

    The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), commonly known as Superfund, was enacted by Congress on December 11, 1980. This law created a tax on the chemical and petroleum industries and provided broad Federal authority to respond directly to releases or threatened releases of hazardous substances that may endanger public health or the environment. Over five years, $1.6 billion was collected and the tax went to a trust fund for cleaning up abandoned or uncontrolled hazardous waste sites. The Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA):

    • established prohibitions and requirements concerning closed and abandoned hazardous waste sites;

    • provided for liability of persons responsible for releases of hazardous waste at these sites; and

    • established a trust fund to provide for cleanup when no responsible party could be identified.

    The law authorizes two kinds of response actions:

    • Short-term removals, where actions may be taken to address releases or threatened releases requiring prompt response.

    • Long-term remedial response actions, that permanently and significantly reduce the dangers associated with releases or threats of releases of hazardous substances that are serious, but not immediately life threatening. These actions can be conducted only at sites listed on EPA's National Priorities List .

    CERCLA also enabled the revision of the National Contingency Plan (NCP). The NCP provided the guidelines and procedures needed to respond to releases and threatened releases of hazardous substances, pollutants, or contaminants. The NCP also established the National Priorities List.

    CERCLA was amended by the Superfund Amendments and Reauthorization Act  on October 17, 1986.

    U.S. House of Representatives U.S. Code - Title 42



    Acid rain


    About the Office of Air and Radiation (OAR)

    Related Information

    Contact OAR

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    Your Air Quality

    Your UV Index

    National Analytical Radiation Environmental Laboratory

    National Vehicle and Fuel Emissions Laboratory

    National Center for Radiation Field Operations

    OAR Press Releases

    All news releases

    What We Do

    The Office of Air and Radiation (OAR) develops national programs, policies, and regulations for controlling air pollution and radiation exposure. OAR is concerned with:

    pollution prevention and energy efficiency,

    indoor and outdoor air quality,

    industrial air pollution,

    pollution from vehicles and engines,


    acid rain,

    stratospheric ozone depletion,

    climate change, and

    radiation protection.

    OAR is responsible for administering the Clean Air Act, the Atomic Energy Act, the Waste Isolation Pilot Plant Land Withdrawal Act, and other applicable environmental laws.

    What is Acid Rain?

    Acid rain, or acid deposition, is a broad term that includes any form of precipitation with acidic components, such as sulfuric or nitric acid that fall to the ground from the atmosphere in wet or dry forms.  This can include rain, snow, fog, hail or even dust that is acidic.  

    What Causes Acid Rain?


    This image illustrates the pathway for acid rain in our environment: (1) Emissions of SO2 and NOx are released into the air, where (2) the pollutants are transformed into acid particles that may be transported long distances. (3) These acid particles then fall to the earth as wet and dry deposition (dust, rain, snow, etc.) and (4) may cause harmful effects on soil, forests, streams, and lakes.

    Acid rain results when sulfur dioxide (SO2) and nitrogen oxides (NOX) are emitted into the atmosphere and transported by wind and air currents. The SO2 and NOX react with water, oxygen and other chemicals to form sulfuric and nitric acids.  These then mix with water and other materials before falling to the ground.

    While a small portion of the SO2 and NOX that cause acid rain is from natural sources such as volcanoes, most of it comes from the burning of fossil fuels.  The major sources of SO2 and NOX in the atmosphere are:

    Burning of fossil fuels to generate electricity.  Two thirds of SO2 and one fourth of NOX in the atmosphere come from electric power generators.

    Vehicles and heavy equipment.

    Manufacturing, oil refineries and other industries.

    Winds can blow SO2 and NOX over long distances and across borders making acid rain a problem for everyone and not just those who live close to these sources. 


    Forms of Acid Deposition

    Wet Deposition

    Wet deposition is what we most commonly think of as acid rain. The sulfuric and nitric acids formed in the atmosphere fall to the ground mixed with rain, snow, fog, or hail.  

    Dry Deposition

    Acidic particles and gases can also deposit from the atmosphere in the absence of moisture as dry deposition. The acidic particles and gases may deposit to surfaces (water bodies, vegetation, buildings) quickly or may react during atmospheric transport to form larger particles that can be harmful to human health. When the accumulated acids are washed off a surface by the next rain, this acidic water flows over and through the ground, and can harm plants and wildlife, such as insects and fish.

    The amount of acidity in the atmosphere that deposits to earth through dry deposition depends on the amount of rainfall an area receives.  For example, in desert areas the ratio of dry to wet deposition is higher than an area that receives several inches of rain each year.


    Measuring Acid Rain


    Acidity and alkalinity are measured using a pH scale for which 7.0 is neutral. The lower a substance's pH (less than 7), the more acidic it is; the higher a substance's pH (greater than 7), the more alkaline it is. Normal rain has a pH of about 5.6; it is slightly acidic because carbon dioxide (CO2) dissolves into it forming weak carbonic acid.  Acid rain usually has a pH between 4.2 and 4.4.

    Policymakers, research scientists, ecologists, and modelers rely on the National Atmospheric Deposition Program’s (NADP) National Trends Network (NTN) for measurements of wet deposition. The NADP/NTN collects acid rain at more than 250 monitoring sites throughout the US, Canada, Alaska, Hawaii and the US Virgin Islands. Unlike wet deposition, dry deposition is difficult and expensive to measure. Dry deposition estimates for nitrogen and sulfur pollutants are provided by the Clean Air Status and Trends Network (CASTNET). Air concentrations are measured by CASTNET at more than 90 locations.

    When acid deposition is washed into lakes and streams, it can cause some to turn acidic. The Long-Term Monitoring (LTM) Network measures and monitors surface water chemistry at over 280 sites to provide valuable information on aquatic ecosystem health and how water bodies respond to changes in acid-causing emissions and acid deposition.




    According to the NOAA, Climate Science Literacy is an understanding of your influence on climate and climate’s influence on you and society. a climate-literate person: 

    • understands the essential principles of Earth’s climate system,

    • knows how to assess scientifically credible information about climate, 

    • communicates about climate and climate change in a meaningful way, and 

    • is able to make informed and responsible decisions with regard to actions that may affect climate. 


    Why does it matter to have Climate Science Literacy? 

    • during the 20th century, Earth’s globally averaged surface temperature rose by approximately 1.08°F (0.6°c). additional warming of more than 0.25°F (0.14°c) has been measured since 2000. Though the total increase may seem small, it likely represents an extraordinarily rapid rate of change compared to changes in the previous 10,000 years. 

    • Over the 21st century, climate scientists expect Earth’s temperature to continue increasing, very likely more than it did during the 20th century. Two anticipated results are rising global sea level and increasing frequency and intensity of heat waves, droughts, and floods. These changes will affect almost every aspect of human society, including economic prosperity, human and environmental health, and national security. 

    • Scientific observations and climate model results indicate that human activities are now the primary cause of most of the ongoing increase in Earth’s globally averaged surface temperature.

    climate change will bring economic and environmental challenges as well as opportunities, and citizens who have an understanding of climate science will be better prepared to respond to both. 

    • Society needs citizens who understand the climate system and know how to apply that knowledge in their careers and in their engagement as active members of their communities. 

    • climate change will continue to be a significant element of public discourse. Understanding the essential principles of climate science will enable all people to assess news stories and contribute to their everyday conversations as informed citizens.


     “Science, mathematics, and technology have a profound impact on our individual lives and our culture. They play a role in almost all human endeavors, and they affect how we relate to one another and the world around us. . . . Science Literacy enables us to make sense of real-world phenomena, informs our personal and social decisions, and serves as a foundation for a lifetime of learning.” From the American association for the Advancement of Science, Atlas of Science Literacy, Volume 2, Project 2061. 


    People who are climate science literate know that climate science can inform our decisions that improve quality of life. They have a basic understanding of the climate system, including the natural and human-caused factors that affect it. Climate science literate individuals understand how climate observations and records as well as computer modeling contribute to scientific knowledge about climate. They are aware of the fundamental relationship between climate and human life and the many ways in which climate has always played a role in human health. They have the ability to assess the validity of scientific arguments about climate and to use that information to support their decisions.


    Climate Changes throughout its history, Earth’s climate has varied, reflecting the complex interactions and dependencies of the solar, oceanic, terrestrial, atmospheric, and living components that make up planet Earth’s systems. For at least the last million years, our world has experienced cycles of warming and cooling that take approximately 100,000 years to complete. Over the course of each cycle, global average temperatures have fallen and then risen again by about 9°F (5°c), each time taking Earth into an ice age and then warming it again. This cycle is believed to be associated with regular changes in Earth’s orbit that alter the intensity of solar energy the planet receives. Earth’s climate has also been influenced on very long timescales by changes in ocean circulation that result from plate tectonic movements. Earth’s climate has changed abruptly at times, sometimes as a result of slower natural processes such as shifts in ocean circulation, sometimes due to sudden events such as massive volcanic eruptions. Species and ecosystems have either adapted to these past climate variations or perished. While global climate has been relatively stable over the last 10,000 years—the span of human civilization— regional variations in climate patterns have influenced human history in profound ways, playing an integral role in whether societies thrived or failed. We now know that the opposite is also true: human activities— burning fossil fuels and deforestation of  large areas of land, for instance—have had a profound influence on Earth’s climate. In its 2007 Fourth assessment, the Intergovernmental Panel on climate change (IPcc) stated that it had “very high confidence that the global average net effect of human activities since 1750 has been one of warming.” The IPcc attributes humanity’s global warming influence primarily to the increase in three key heat-trapping gasses in the atmosphere: carbon dioxide, methane, and nitrous oxide. The U.S. climate change Science Program published findings in agreement with the IPcc report, stating that “studies to detect climate change and attribute its causes using patterns of observed temperature change in space and time show clear evidence of human influences on the climate system (due to changes in greenhouse gasses, aerosols, and stratospheric ozone).”To protect fragile ecosystems and to build sustainable communities that are resilient to climate change— including extreme weather and climate events—a climate-literate citizenry is essential. This climate science literacy guide identifies the essential principles and fundamental concepts that individuals and communities should understand about Earth’s climate system. Such understanding improves our ability to make decisions about activities that increase vulnerability to the impacts of climate change and to take precautionary steps in our lives and livelihoods that would reduce those vulnerabilities.