A
Ablation
The loss of snow and ice from a glacier or ice sheet by melting and evaporation.
Adaptation
In the context of climate change, action taken to prepare for unavoidable climate changes that are currently happening or are projected to happen in the future.
Ablation zone
The front part of a glacier, where ice is lost due to melting and calving.
Acadian Orogeny
A Devonian mountain-building event involving the collision of the east coast of North America and the accreted terrane of Avalon. The event caused metaphorphism, folding, and faulting in an area from New York to Newfoundland; sediments eroded from the mountains accumulated in thick strata, the Catskill Delta, in the Appalachian Basin of New York and Pennsylvania. See also orogeny.
Acanthodian
A class of extinct fish, bearing a superficial resemblance to sharks, and sharing features with both bony and cartilaginous fish. Acanthodian skin was covered with tiny, spiny scales.
Accretion, accrete
The process by which a body of rock increases in size due to the addition of further sedimentary particles or of large chunks of land, such as terranes.
Accretionary prism
A pile of sediments and ocean crust, scraped off a descending plate during subduction, and piled onto the overlying continental crust.
Accumulation zone
The highly elevated part of a glacier, where annual snow accumulation outpaces snow loss.
Acid rain
Rain or other precipitation that contains high amounts of sulfuric and nitric acid. It occurs when sulfur dioxide and nitrogen oxide react with water, oxygen, and other chemicals in the atmosphere to form these acidic compounds. Acid rain can cause damage to trees, soils, and entire ecosystems, as well as accelerating the decay of human works such as paint and building materials.
Active plate boundary, active plate margin
The boundary between two plates of the Earth’s crust that are colliding, pulling apart, or moving past each other.
See also: plate tectonics.
Adaptive radiation
Process in which many new species evolve, adapting to vacant ecological niches in a relatively short interval of geological time. Examples occur across a range of scales, from the diversification of numerous species from a single species (e.g., Galapagos finches) to the diversification of higher taxa into previously unoccupied environments or into niches vacated through mass extinction (e.g., mammals after the extinction of dinosaurs).
Aeolian
Pertaining to, caused by, or carried by the wind. Aeolian sediments are often polished, giving them a “frosty” appearance. The name comes from Aeolus, the Greek god of wind.
Aerobic
Involving free oxygen.
Aerosol
Tiny solid or liquid particles in the air. Examples include dust, smoke, mist, and human-made substances such as particles emitted from factories and cars.
Agate
A crystalline silicate rock with a colorful banded pattern. It is a variety of chalcedony ( quartz ). Agates usually occur as nodules in volcanic rock.
Aggregate
Crushed stone or naturally occurring unlithified sand and gravel, used for construction, agriculture, and industry. Aggregate properties depends on the properties of the component rock. Rock quarried for crushed stone includes, for example, granite and limestone.
Albedo
The fraction of solar energy that a surface reflects back into space.
Alfisols
A soil order; these are highly fertile and productive agricultural soils in which clays often accumulate below the surface. They are found in humid and subhumid climates.
Alkalic basalt
A fine-grained dark basaltic lava containing a high proportion of silicates, and relatively high in sodium and potassium. See also: basalt, lava, silica.
Alleghanian Orogeny
A Carboniferous to Permian mountain-building event involving the collision of the eastern coast of North America and northwestern coast of Africa (then part of Gondwana ). The event caused a combination of metaphorphism, folding, and faulting in an area from Alabama to Newfoundland. The orogeny resulted in the Appalachian and Allegheny Mountains, which are heavily eroded remnants of the original mountains formed by the event. See also orogeny.
Alluvium, alluvial
A layer of river-deposited sediment.
Aluminum (Al)
A metallic chemical element (Al), and the most abundant metal in the Earth’s crust.
Aluminium has a low density and an excellent ability to resist corrosion. Structural components made from the metal and its alloys are commonly used in the aerospace industry, transportation, and household goods.
Amber
A yellow or yellowish-brown hard translucent fossil resin that sometimes preserves small soft-bodied organisms inside.
Ammonoid
A group of extinct cephalopods belonging to the Phylum Mollusca, and possessing a spiraling, tightly-coiled shell characterized by ridges, or septa.
Learn more: Digital Encyclopedia of Ancient Life, Quick Guide to Common Fossils
Amniotes
The group of tetrapods distinguished from amphibians by the development of an egg capable of maturing entirely out of water. Amniotes include the reptiles, birds, and mammals.
Amphibole
A group of dark-colored silicate minerals, or either igneous or metamorphic origin.
Learn more: Digital Encyclopedia of Earth Science
Anapsid
A type of tetrapod vertebrate whose skull has no openings near the temple. Anapsids are the most primitive subclass of reptile.
Andesite
A fine-grained extrusive volcanic rock, with a silica content intermediate between that of basalt and dacite.
Learn more: Virtual Collection
Andisols
A soil order; these are highly productive soils often formed from volcanic materials. They possess very high water- and nutrient-holding capabilities, and are commonly found in cool areas with moderate to high levels of precipitation.
Anorthosite
A plutonic igneous rock made mostly of plagioclase feldspar. Most anorthosite rocks were formed in the Proterozoic eon (Precambrian).
Anthracite
A dense, shiny coal that has a high carbon content and little volatile matter. Anthracite is as much as 95% carbon. Found in deformed rocks, anthracite is the cleanest burning of the three types of coal, because it contains the highest amount of pure carbon.
Anthropogenic
Made by humans, or resulting from human activity.
Antler Orogeny
A period of mountain building that deformed rocks in a belt extending from the California - Nevada border northward into Idaho. The Antler Orogeny began began in the late Devonian and continued into the Carboniferous. See also orogeny.
Anticline
A layer of rock folded (bent) along an axis, concave side down (i.e., in an upside down "U" or "V" shape). Thus rocks at the center of the anticline, along the fold (crest), are lifted up relative to the rest of the layer.
Antimony (Sb)
A lustrous gray metallic element (Sb), mainly found in nature as the sulfide mineral stibnite (Sb2S3). Antimony compounds have been known since ancient times, when it was used in cosmetics. Today, the largest applications for the element are as an alloying material for lead and tin, and for plates in lead-acid batteries.
Appalachian Basin
An inland basin, formed by the Taconic and Acadian mountain-building events. The crust was downwarped as a result of the colliding plates, and the basin was later filled with an inland sea.
Aquifer
A water-bearing formation of gravel, permeable rock, or sand that is capable of providing water, in usable quantities, to springs or wells.
Archaeocete
A member of a group of primitive whales that lived during the Eocene and Oligocene epochs. The earliest members of the group are from the Indo-Pakistan region and were only partially aquatic.
Archaeocyathid
A vase-shaped organism with a carbonate skeleton, generally believed to be a sponge. Archaeocyathids were the first important animal reef builders, originating in the early Cambrian. They were very diverse, but went extinct by the end of the Cambrian. Archeocyathids are often easiest to recognize in limestones, by their distinctive cross-sections.
Learn more: Digital Encyclopedia of Ancient Life
Archean
A geologic time interval that extends from 4 billion to 2.5 billion years ago. It is part of the Precambrian.
Arête
A thin ridge of rock with an almost knife-like edge, formed when two glaciers erode parallel valleys.
Aridisols
A soil order; these are formed in very dry (arid) climates. The lack of moisture restricts weathering and leaching, resulting in both the accumulation of salts and limited subsurface development. They are commonly found in deserts.
Artesian
A channel that releases pressure from an aquifer, allowing the aquifer’s internal pressure to push the water up to the surface without the aid of a pump.
Arthropod
An invertebrate animal, belonging to the Phylum Arthropoda, and possessing an external skeleton (exoskeleton), body segments, and jointed appendages. Arthropods include crustaceans, arachnids, and insects, and there are over a million described arthropod species living today. Trilobites are a major group of extinct arthropods.
Asbestos
A fibrous silicate mineral that is resistant to heat, flames, and chemical action. As a very slow conductor of heat, asbestos was once commonly used as a fireproofing material and electrical insulation. Concerns over its health effects on the lungs have led to its removal from most common uses.
Asphalt
A black, sticky, semi-solid, and viscous form of petroleum.
Asthenosphere
A thin, semifluid layer of the Earth, below the outer rigid lithosphere, forming much of the upper mantle. The heat and pressure created by the overlying lithosphere make the solid rock of the asthenosphere bend and move like metal when heated. The layer is thought to flow vertically and horizontally with circular convection currents, enabling sections of lithosphere to subside, rise, and undergo lateral movement.
Atmosphere
A layer of gases surrounding a planet. Earth’s atmosphere protects living organisms from damage by solar ultraviolet radiation, and it is mostly composed of nitrogen. Oxygen is used by most organisms for respiration. Carbon dioxide is used by plants, algae, and cyanobacteria for photosynthesis.
Atoll
A circular or horseshoe-shaped coral reef, surrounded by deep water and enclosing a shallow lagoon. The rim of the coral often extends above the water, sometimes creating a small beach or sandbar. Atolls tend to form as reefs grow around the rim of extinct volcanoes. As the volcanic peak erodes and the volcano subsides beneath the water’s surface, the reef grows upward and a lagoon is formed within the reef. Atolls range in diameter from 1 kilometer (0.6 miles) to more than 130 kilometers (81 miles).
See also: caldera, erosion, reef, scleractinian coral
Availability heuristic
The reliance on immediate examples rather than information grounded in extensive data or research, when looking for explanations.
Avalon
An early Paleozoic microcontinent offshore of what is now the eastern coast of North America. Avalon collided with and became the eastern edge of North America during the Acadian Orogeny.
B
Backfire effect
An effect that causes beliefs to become stronger rather than weaker when they are challenged with conflicting evidence. The backfire effect is in part a response to identity protective cognition, the status quo bias, and allegiance to community norms, each of which are powerful forces that resist change.
Bacteria
Single-celled microorganisms with cell walls but without organelles or a nucleus.
Banded iron formations
Geologic formations comprised of layers of Precambrian, iron-rich, sedimentary rock.
Basalt
An extrusive igneous rock, and the most common rock type on the surface of the Earth. It forms the upper surface of all oceanic plates, and is the principal rock of ocean/seafloor ridges, oceanic islands, and high-volume continental eruptions. Basalt is fine-grained and mostly dark-colored, although it often weathers to reds and browns because of its high iron content.
Biomass energy
Energy produced by burning plants, wastes, or their derivatives.
Biosphere
All plants, animals, and people, both living and non-living, on Earth.
Bolide
An extraterrestrial object of any composition that forms a large crater upon impact with the Earth. In astronomy, bolides are bright meteors (also known as fireballs) that explode as they pass through the Earth’s atmosphere.
Brownout
A situation where available electric power is limited but not eliminated.
C
Cambrian
A geologic time period lasting from 541 to 485 million years ago. During the Cambrian, multicellular marine organisms became increasingly diverse, as did their mineralized fossils. The Cambrian is part of the Paleozoic Era.
Carbon cycle
The exchange and recycling of carbon between the geosphere, hydrosphere, atmosphere, and biosphere.
Carbon sink
A system or part of a system which absorbs carbon.
Carbon-14
An isotope of carbon often used in dating materials.
Carboniferous
A geologic time period that extends from 359 to 299 million years ago. It is divided into two subperiods, the Mississippian and the Pennsylvanian. By the Carboniferous, terrestrial life had become well established.
Cenozoic
The geologic time period spanning from 66 million years ago to the present. The Cenozoic is also known as the age of mammals, since extinction of the large reptiles at the end of the Mesozoic allowed mammals to diversify. The Cenozoic includes the Paleogene, Neogene, and Quaternary periods.
Chemical weathering
The breaking down of rock through chemical processes.
Chlorofluorocarbons
Compounds of carbon, hydrogen, chlorine, and fluorine, usually anthropogenic gases used as refrigerants or in aerosol cans. Released into the atmosphere, these compounds are greenhouse gases and are responsible for the ozone hole.
Climate
A description of both the average weather conditions (temperature, precipitation, wind, etc.) and the extremes that a region experiences.
Climate change
The current increase in the average surface temperature worldwide, caused by the buildup of greenhouse gases in the atmosphere, and the related changes to other aspects of climate such as precipitation patterns and storm strength. See also global warming.
Climate change adaptation
Actions taken to prepare for climate changes that are occurring or will occur in the future.
Climate change mitigation
Actions taken to limit or eliminate emissions of greenhouse gases in order to reduce future climate warming.
Climate gradient
Changes in climate across a distance.
Climate model
A computer-generated simulation of the Earth's climate system, projected through time.
Climate normal
Thirty-year averages of variables such as daily temperature, rainfall, snowfall, and frost and freeze dates that can be compared with thirty-year averages of these variables from other time periods.
Cloud
A visible aggregation of condensed water vapor in the atmosphere.
Coal
A rock formed from ancient plant matter that can be burned as fuel. Since coal is formed from fossilized plant remains it is considered a fossil fuel.
Co-benefit
Sometimes called multiple benefit, is an improvement or positive outcome from an action that was not the primary one intended. For example, a person might choose to use a highly energy-efficient appliance in order to reduce energy use and thus carbon emissions, and saving money might be a co-benefit of this choice.
Cognitive bias
A holding on to incorrect thinking even in the presence of contrary information, because of beliefs or points of view one has.
Combined heat and power
An approach that uses a single fuel source to generate both electricity and usable heat. Combined heat and power systems are typically located near where the energy is consumed, and they use the heat which is wasted in traditional electrical power generation processes.
Condensation nuclei
Suspended particles in the air which can serve as "seeds" for water molecules to attach to, the first step in the formation of clouds. See also nucleation sites.
Confirmation bias
The tendency to seek out information that agrees with one’s existing prior opinions, and to ignore established evidence that might conflict with those opinions. See also myside bias.
Continental divide
A ridge of high land on a continent, which separates regions where water flows to oceans or seas on different sides of the continent.
Convection
Movement of a fluid, such as air or water, resulting from gravitational force on the fluid. Warmer, less dense matter rises and cooler, more dense matter sinks, producing heat transfer.
Convection cell
A zone where warm, less dense air or water rises and cool, more dense air or water sinks, creating a repetitive pattern of motion.
Coriolis effect
The apparent deflection of air masses in the atmosphere, which are moving relative to the rotating reference frame of the Earth.
Coriolis force
A force acting on objects (e.g. air masses in the atmosphere) that are moving relative to a rotating reference frame (e.g., the Earth)
Cretaceous
A geologic time interval spanning from 144 to 66 million years ago. It is the youngest period of the Mesozoic. The end of the Cretaceous bore witness to the mass extinction event that resulted in the demise of the dinosaurs.
Cryosphere
The part of Earth’s surface where water exists in solid form. This includes all major forms of ice, such as sea ice, glaciers, ice sheets, and permafrost.
Current
Directional movement of a fluid mass.
Cycad
A palm-like, terrestrial seed plant (tree) belonging to the Class Cycadopsida, and characterized by a woody trunk, a crown of stiff evergreen leaves, seeds without protective coatings, and no flowers. Cycads were very common in the Mesozoic, but are much reduced in diversity today, restricted to the tropical and subtropical regions of the planet.
D
Deciduous plants
Plants which lose their leaves, typically in autumn, and regrow them the following spring.
Devonian
A geologic time period spanning from 419 to 359 million years ago. The Devonian is also called the "age of fishes" due to the diversity of fish that radiated during this time. On land, seed-bearing plants appeared and terrestrial arthropods became established. The Devonian is part of the Paleozoic.
Dinosaur
A member of a group of terrestrial reptiles with a common ancestor and thus certain anatomical similarities, including long ankle bones and erect limbs. All of the large reptile groups, including the dinosaurs, disappeared at or before the mass extinction at the end of the Cretaceous.
Drought
A long period of unusually low rainfall, resulting in lack of water for plants, animals, and people.
Duration
The length of time an event or activity lasts.
E
Eccentricity
The shape of Earth's orbit around the Sun, which varies in the shape of an ellipse on a 100,000-year cycle
Ecosystem services
The numerous benefits that healthy ecosystems provide to people, such as food, medicine sources, raw materials, erosion control, waste decomposition, filtering pollutants out of air and water, and recreation opportunities.
El Niño
Also called the El Niño – Southern Oscillation (ENSO); is represented by fluctuating temperatures and air pressures in the tropical Pacific Ocean. During an El Niño event, the eastern Pacific experiences warmer water and higher air pressure than the western Pacific, changing rainfall patterns, eastern Pacific upwelling, and weather variables globally. ENSO events typically occur every 3 to 7 years.
Energy balance
A state in which the energy coming in to a system equals the energy going out.
Energy conservation
An approach to processes and activities that results in using less energy, on scales ranging from individual to industrial to national and global.
Energy efficiency
Methods which enable machines to perform functions while minimizing energy loss or using less energy than previously.
Eocene
A geologic time interval extending from 56 to 33 million years ago. The Eocene is an epoch of the Paleogene period.
Equilibrium
A state of balance in opposing forces, amounts, or rates.
Esker
A sinuous, elongated ridge of sand and gravel. Most eskers formed within ice-walled tunnels carved by streams flowing beneath a glacier. After the ice melted away, the stream deposits remained as long winding ridges. Eskers are sometimes mined for their well-sorted sand and gravel.
Evapotranspiration
A combination of evaporation of liquid water on plant leaves and in the soil around the plant and transpiration, the transfer of water from a plant’s roots to its leaves and then to water vapor in the air. Evapotranspiration cools the air because it takes heat from the air to convert liquid water to water vapor.
F
Feedback
The response of a system to some change that either balances/opposes or reinforces/enhances the change that is applied to a system. Balancing feedback (sometimes called negative feedback) tends to push a system toward stability; reinforcing feedback (sometimes called positive feedback) tends to push a system towards extremes.
Feedback loop
A repeating process where some of the output of a system becomes input as well.
Feldspar
An extremely common group of rock-forming minerals found in igneous, metamorphic, and sedimentary rocks. There are two groups of feldspar: alkali feldspar (which ranges from potassium-rich to sodium-rich) and plagioclase feldspar (which ranges from sodium-rich to calcium-rich). Potassium feldspars of the alkali group are commonly seen as pink crystals in igneous and metamorphic rocks, or pink grains in sedimentary rocks. Plagioclase feldspars are more abundant than the alkali feldspars, ranging in color from light to dark. Feldspars are commercially used in ceramics and scouring powders.
Learn more: Silicate Minerals.
Fission
The process of bombarding atomic nuclei with neutrons, splitting the nuclei into those of lighter elements and more neutrons, and also resulting in the release of energy.
Floodplain
The land around a river that is prone to flooding. This area can be grassy, but the sediments under the surface are usually deposits from previous floods.
Flue gas separation
A process which uses a liquid solvent to chemically remove CO₂ molecules from a gas as the molecules make their way through a flue.
Forcing
A change that has a directional impact on what is being changed (e.g., a solar forcing on the Earth directly impacts the Earth's heat absorption).
Fossil fuel
A non-renewable, carbon-based fuel source like oil, natural gas, or coal, developed from the preserved remains of fossil organisms.
G
Geoengineering
A large-scale technological effort to change the Earth’s climate, typically either by removing carbon dioxide from the atmosphere or by blocking incoming solar radiation.
Geosphere
The solid portion of the Earth.
Geothermal energy
Heat energy found below the surface of the Earth.
Ginkgo
A terrestrial tree belonging to the plant division Ginkgophyta, and characterized by broad fan-shaped leaves, large seeds without protective coatings, and no flowers. Ginkgos were very common and diverse in the Mesozoic, but today only one species exists, Ginkgo biloba.
Glacial
A time in Earth's history when a cold climate leads to the advance of glaciers and ice sheets. See also interglacial.
Glacial-interglacial cycle
An alternation between times in Earth's history when glaciers and ice sheets advance and ice is present at the poles (glacials), and times when the climate is warmer and no ice is present at the poles (interglacials).
Glacier
A very large piece of ice that sits at least partially on land and moves under the force of gravity.
Global warming
The current increase in the average temperature worldwide, caused by the buildup of greenhouse gases in the atmosphere. With the coming of the Industrial Age and exponential increases in human population, large amounts of gases have been released into the atmosphere (especially carbon dioxide) that give rise to global warming. The term climate change is preferred because warming contributes to other climatic changes such as precipitation and storm strength.
Goldilocks principle
The idea that the temperature on Earth is not too hot and not too cold, but "just right" for life as we know it to exist.
Gondwana
The supercontinent of the Southern Hemisphere, composed of Africa, Australia, India, and South America. It combined with the North American continent to form Pangaea during the late Paleozoic.
Gradient
A change, either increasing or decreasing, in the magnitude of a quantity over space or time.
Green infrastructure
Structures that use plants, soil, and other natural features to perform functions such as providing shade, absorbing heat, blocking wind, or absorbing and filtering stormwater.
Greenhouse effect
The retention of heat, due to greenhouse gas molecules in Earth's atmosphere, of some of the heat energy absorbed by the Earth that would otherwise escape into space.
Greenhouse gas
A gas, located in Earth’s atmosphere, that absorbs and re-radiates energy in the form of heat; carbon dioxide, water vapor, and methane are examples.
Gulf stream
A current in the Atlantic Ocean which transports warm water from the Gulf of Mexico along North America's East Coast, then across the Atlantic in two streams, one traveling to Northern Europe and one to West Africa.
Gypsum
A soft, sulfate mineral that is widely mined for its use as fertilizer and as a constituent of plaster. Alabaster, a fine-grained light colored variety of gypsum, has been used for sculpture making by many cultures since ancient times.
Gyre
Large- (i.e., global-) scale rotating masses of ocean water.
H
Heat island
An urban area which experiences higher temperatures than do surrounding rural areas as a result of pollution, pavement, and the surfaces of buildings magnifying localized heating.
Heat wave
A prolonged period of extremely high air temperatures.
Heinrich events
Periods during the last 100,000 years where large volumes of freshwater entered the ocean from icebergs which broke off glaciers and ice sheets in the Arctic and floated into the North Atlantic Ocean. This release of freshwater changed ocean circulation because freshwater and seawater have different densities.
Holocene
The most recent portion of the Quaternary, beginning about 11,700 years ago and continuing to the present. It is the most recent (and current) interglacial, an interval of glacial retreat. The Holocene also encompasses the global growth and impact of the human species.
Horsetail
A terrestrial plant belonging to the Family Equisetaceae in the plant division Pteridophyta, and characterized by hollow, jointed stems with reduced, unbranched leaves at the nodes.
Hurricane
A rapidly rotating storm system with heavy winds, a low-pressure center, and a spiral arrangement of thunderstorms. These storm systems tend to form over the tropical ocean, and are classified as hurricanes, typhoons, or cyclones (depending on their location in the world) once winds have reached 199 kilometers per hours (74 miles per hour). See also tropical cyclone.
Hydropower
Electric power derived from the kinetic energy of falling or moving water.
Hydrosphere
All of the water on Earth.
I
Ice core
A large cylinder of ice extracted from an ice sheet or glacier, such as is found in Antarctica, Greenland, or on very high mountains worldwide. Chemical analysis of the ice and air bubbles can reveal information about the climate at the time the ice formed, as can materials such as dust or pollen found in the ice.
Ice sheet
A mass of glacial ice that covers part of a continent and has an area greater than 50,000 square kilometers (19,000 square miles).
Iceberg
A large chunk of ice, generally ranging in height from 1 to 75 meters (3 to 246 feet) above sea level, that has broken off of an ice sheet or glacier and floats freely in open water.
Identity-protective cognition
A way of thinking that drives us to select the evidence that is consistent with the worldview of our social groups, sometimes leading us to believe certain things that are demonstrably false.
Infrared
Electromagnetic radiation in the part of the spectrum with wavelengths from 750 nanometers to 1 millimeter. People sense infrared radiation as heat.
Inland sea
A shallow sea covering the central area of a continent during periods of high sea level. An inland sea is located on continental crust, while other seas are located on oceanic crust.
Insolation
The amount of solar radiation reaching the Earth.
Interglacial
A time in Earth’s history between glacial advances; there have been about 50 glacial advances and interglacials in the past 2.5 million years.
Ionizing radiation
High-energy electromagnetic energy which can cause ionization in the material through which it passes, for example, x-rays and gamma rays.
IPCC
The Intergovernmental Panel on Climate Change, a large, international group of climate scientists working to understand climate change and to present reliable climate data and information to policy-makers and the public at large.
Iron oxide minerals
A range of minerals containing chemical compounds of iron and oxygen.
Irradiance
The intensity of radiated energy received, for example, by the Earth from the Sun.
Isotope
A form of an element that contains a specific number of neutrons. For example, the isotope of carbon with six neutrons is known as carbon-12 (12C) and the isotope of carbon with eight neutrons is carbon-14 (14C).