Abiotic: Nonliving part of the environment.
Abyssal plain: Vast, flat areas of the deep-ocean floor.
Abyssopelagic zone: The deep ocean that extends from 13,000 feet (4,000 meters) below the surface to the seafloor.
Acid deposition: The collective term for dry deposition and wet deposition of acids as a result of air pollution.
Acid rain: The result of acidic chemicals reacting in the atmosphere with water and returning to Earth as contaminated rain, fog, or snow.
Aeration: Adding oxygen, nitrogen, and other gasses necessary for respiration into water.
Agar: A mixture of sugars found in some types of seaweed that can form a solid surface used in laboratories to grow bacteria.
Air mass: Large body of air with only small variations of temperature, pressure, and moisture.
Air pressure: Force exerted by the weight of a column of air above a particular location.
Algae: Fresh and salt water plants that can convert the Sun’s energy into food; they range in size from microscopic cells to forms that are bigger than a person.
Algal bloom: The rapid and huge increase in numbers of algae that can occur in the presence of a food source such as phosphorus.
Alpine glacier: Mass of moving ice that is confined by mountain valleys.
Ambergris: A highly prized fat found in the intestines of some whales.
Anadromous: Fish that are born in fresh water and then move to marine water as adults.
Annelid: A segmented worm such as an earthworm or a poly-chaete worm.
Antarctic ice cap: Ice covering the continent of Antarctic and Southern Ocean region around the South Pole.
Anticyclone: An atmospheric system associated with dry, clear weather with winds that spiral out away from a center of high atmospheric pressure.
Aquarist: Person who keeps an aquarium.
Aquatic: Relating to water.
Aqueduct: A channel or conduit, usually resembling a bridge, that carries water on land or over a valley, from a higher point to a lower one.
Aquiclude: Permeable (leaky) layers of rock or soil that confine and pressurize groundwater within aquifers.
Aquifer: An underground rock formation that contains water.
Archaeological context: The natural surroundings, physical location, and cultural origin of archaeological artifacts or sites.
Archimedes principle of buoyancy: An object submerged in a fluid is pushed upward by a buoyant force equal to the weight of the fluid it displaces.
Arctic: Region of the Earth between the North Pole and the Arctic circle.
Arctic Circle: Invisible circle around the North Pole above latitude at 66°33′ North.
Arctic ice cap: Ice covering the Arctic Ocean and land areas north of the Arctic Circle in the North Pole.
Arid: Lack of rainfall. An arid climate has an annual rainfall of only 10 inches or less per year.
Artesian flow: Water that rises to the land surface from confined aquifers without pumping.
Arthropod: A member of a group of invertebrates that has jointed appendages and an external skeleton.
Artifact: Any object made or modified by humans.
Atmosphere: A unit to measure pressure; one atmosphere is 14.7 pounds per square inch, which is the standard atmospheric pressure measured at sea level.
Atmospheric (barometric) pressure: Pressure caused by the weight of the atmosphere over a surface or object.
Atoll: Ring-shaped coral island that surrounds a shallow lagoon.
Atom: The smallest unit that has all the chemical and physical characteristics of an element.
Autecology: Ecological study of individual organisms or individual species.
Autonomous underwater vehicle (AUV): Remote-controlled motorized crafts that are designed to study and withstand the pressure of the deep ocean.
Autotroph: Organism that uses inorganic substances to produce energy.
Bacterioplankton: Plankton composed of bacteria, often serving as the basis of the aquatic food chain.
Baleen: Bristly plates that hang from the upper jaws of baleen whales; acts like a sieve for the microscopic animals during feeding.
Ballast water: Water that is pumped into the hull of a ship to keep the ship balanced correctly in the water when it is empty.
Barge: Large, usually flat boat used for shipping.
Barometer: An instrument used to measure atmospheric pressure.
Barrage: Artificial obstruction such as a dam constructed in a water channel to increase water depth or divert flow.
Barrier Island: Long, narrow coastal island built up parallel to the mainland.
Basalt: Black iron- and magnesium-rich volcanic rock common in ocean basins.
Base level: The water level at the outlet of a stream, usually sea level; streams cannot erode below this level.
Bathymetry: The three-dimensional shape of the seafloor.
Bathypelagic zone: The layer of the ocean below the mesopelagic zone and above the abyssopelagic zone; generally it extends between 3,250 feet (1,000 meters) and 13,000 feet (4,000 meters) below the surface of the ocean.
Bathyscaphe: A submersible vehicle that is capable of going to the deepest parts of the ocean and withstanding extreme pressure.
Beach: Region of sand or rock that slopes down to the water of a lake or ocean.
Benthic: Animals, plants, and microorganisms that live on the floor of the ocean.
Bioaccumulation: Tendency for substances to increase in concentration in living organisms as they take in contaminated air, water, or food.
Biodiversity: The variety of living organisms and the ecosystems in which they occur.
Bioluminescence: Light that is generated by chemical reactions in bacteria, animals, and plants.
Bioremediation: The use of living organisms such as bacteria to remove pollutants from natural resources, such as water.
Biosphere: All the biological communities (ecosystems) that exist in the world.
Biotic: Living part of the environment.
Black smoker: Underwater seep of volcanic magma that deposits minerals.
Boreal forests: Treed areas of the northern temperate regions of North America, Europe, and Asia that are dominated by evergreen trees like firs, pines, and spruces.
Brackish: Water with a salinity (salt content) between that of freshwater and ocean water.
Braided stream: Streams with many channels that split apart and rejoin.
Brine: Water that contains a high concentration of salt.
Bulk carrier: A ship that carries large quantities of raw material, such as steel, timber, or grain, in large cargo holds.
Buoyancy: Ability of an object to float in a liquid.
Buoyant force: Upward force exerted by a liquid on an object; an object will float if the buoyant force of the liquid is greater than the downward force of gravity.
Caldera lake: Lake filling a large circular depression left by a volcanic eruption or collapse.
Canal: Man-made or artificially improved waterway used for travel, shipping, irrigation, or hydropower.
Canoe: Boat pointed at both ends and typically with an open top, or deck.
Carbonate: Rock or loose sediment composed of the mineral calcite or calcium carbonate.
Cargo: Goods that are being transported.
Cargo hold: A section of a ship that is divided from other sections for the transport of a single type of cargo.
Cartilage: Tough but flexible material, found between bones in humans and in the skeletons of sharks and rays.
Cetacean: A member of the group of marine mammals that includes whales, dolphins, and porpoises.
Channel: The water-filled path of the stream, river, or man-made waterway.
Chemical oceanology: Study of the molecules and atoms that are dissolved in the ocean.
Chemistry: The science of the composition, structure, and properties of matter.
Chemosynthesis: The use of chemicals, rather than sunlight, for the production of food.
Cistern: A man-made reservoir for storing water.
Clearcut: The total removal of trees and much of the vegetation from a section of forest.
Climate: Long-term meteorological conditions or average weather.
Climate effect: Temperature and moisture patterns that characterize a large region over tens, hundreds, or even thousands of years.
Climate zone: Areas of the world with a characteristic climate. Climate zones are described as arid, Mediterranean, mountain, polar, temperate, and tropical.
Cnidarian: A member of a group of invertebrates that includes corals, jellyfish, and sea anemones; these organisms have stinging cells to capture prey.
Coastal zone: The shallow part of the ocean extending from the high-tide mark on land to the edge of the continental shelf.
Coastline: The land that lies next to the sea.
Commercially extinct: When an animal becomes too rare to be worth hunting.
Community: All of the organisms that live in a certain locations.
Compound: Substance in which two or more elements are joined together.
Computer model: Description of a system, theory, or phenomenon entered into a computer that includes its known properties and conditions and can be used to predict future conditions and events within the system.
Condensation: The transformation (phase change) of a gas to a liquid.
Conservation: Protection, management, or restoration of natural resources such as soil, forests, wetlands, minerals, and water.
Container ship: A ship that transports cargo in sealed containers that may be unloaded directly onto trains or trucks.
Contaminant: Polluting substance that has harmful effects on biological life and other natural systems.
Contamination: Polluted or containing unwanted substances.
Continental glacier: Very large, dome-shaped mass of glacial ice that completely covers the terrain beneath it; also called ice sheet.
Continental shelf: The edge of a continent that gently slopes in relatively shallow water before dropping off steeply to the great depths of the open ocean.
Convection: Circulation of a gas or liquid driven by heat transfer and gravity.
Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES): A 1973 treaty that restricts international commerce between participating nations for plant and animal species that are believed to be harmed by trade.
Coral: A rocklike deposit formed of the calcium carbonate skeletons of a group of small sea animals.
Coral reef: Tropical marine feature created by numerous colonies of tiny coral animals; coral reefs contain a great diversity of marine animals.
Coriolis effect: The effect of the Earth’s rotation on the atmosphere and oceans that causes deflection to the right in the northern hemisphere, and deflection to the left in the southern hemisphere.
Crest: The highest point of a wave. Also, the highest level of floodwaters during a flood.
Cretaceous period: A division of geologic time from 65 to 144 million years ago; along with the Jurassic and Triassic, this period comprised the Mesozoic Era known as "the age of the dinosaurs."
Crevasse: A large crack or fissure in the surface of a glacier.
Cruise ship: A large ship, once used as the primary means of transporting people across an ocean, that now serves as a vacation destination, while visiting various ports of interest.
Crustacean: A member of a group of arthropods that includes brine shrimp, barnacles, copepods, shrimp, lobsters, crabs, and euphausids.
Curation: Cleaning, preserving, and storing artifacts recovered from archaeological sites for further study.
Current: The circulation of ocean waters that produces a steady flow of water in a prevailing direction.
Cyclic changes: Changes that repeat themselves over time.
Cyclone: Rotating atmospheric system of winds that flow into a low-pressure center. Cyclones rotate counterclockwise in the northern hemisphere and clockwise in the southern hemisphere.
Dam: A physical barrier constructed across a river or waterway to control the flow or raise the level of water.
Decibel: Unit that measures the loudness or intensity of sound.
Deep-sea fishing: Form of fishing that requires boating several miles out to sea in order to catch fish that live far from shore, such as marlin, tarpon, and barracuda.
Deforestation: Large-scale removal of trees from a woodland.
Delta: The sedimentary deposit that forms at the mouth of a river. Delta means "triangle" in Greek, and river deltas are usually triangular.
Density: The amount of mass-per-unit volume of a substance. In water, density is primarily determined by the combination of salinity and temperature.
Dentricles: V-shaped structures that make up the rough skin of a shark.
Deposition: Process by which dirt, silt, and sand is moved from its original place by wind or water and deposited elsewhere.
Depositional coastline: A coastline formed from the sediment of carbonates, plants, and animals that have hard mineral shells made of calcium carbonate.
Desalination: Process of removing salt from sea water or water contaminated with salt.
Desert: An area of land that receives less than 10 inches (25.4 centimeters) of precipitation per year.
Desertification: Gradual changes that take place over a region or area of land that ultimately result in the formation of a desert.
Detergent: A chemical used as a cleaning agent because it encourages the formation of an oil-in-water emulsion.
Diatoms: Single-celled phytoplankton that produce a thin shell made of silica (glass).
Dinoflagellates: Single-celled phytoplankton that move by propelling whip-like appendages called flagella.
Dipolar molecule: A molecule that has a positive charge at one end and an equal, but opposite, negative charge at the other end.
Discharge zone: Land area where groundwater flows out of aquifers on to land surface.
Dispersant: A chemical agent that reduces the surface tension of liquid hydrocarbons, encouraging the formation of an oil-in-water emulsion. This reduces the volume of residual oil on shorelines or the water surface after a spill.
Dissolution: When water breaks rocks into dissolved chemicals; a form of erosion.
Distillation: The purification of water by heating.
Distributary: Channel of water that runs through deltas.
Diversion: Changing the direction of a water body such as a stream or river by building canals, dams, or channels.
Divide: High point or ridge that separates drainage basins, and in which water flows down in all directions.
Diving suit: Sealed suit that receives a constant supply of air, usually surface air supplied by hoses; used for early ocean dives.
Doldrums: A zone of dead air and still water, usually at the equator where the trade winds and equatorial currents converge.
Downwelling: Ocean zones where surface water sinks into the deep ocean.
Dowsing: Pseudoscientific practice of using alleged spiritual powers and a "divining rod" to locate underground water.
Drag: A force that resists movement.
Drainage basin: Land area from which surface runoff drains into a stream or lake.
Dredge: Device for scooping or digging rock and sediment from the seafloor.
Dredging: A process where a ship drags a hook or grate along the bottom of a waterway in order to remove the accumulated silt and mud.
Drought: A temporary but extended period of abnormally low rainfall.
Dry deposition: Acidic gases and solid particles containing acids that settle out of the air and land on surfaces.
Dynamic equilibrium: State of balance attained by maintaining equal rates of input and withdrawal from a system.
Echinoderm: A member of the group of invertebrates that includes feather stars, sea stars, brittle stars, sea urchins, and sea cucumbers.
Echolocation: The ability of dolphins, bats, and some other animals to detect objects and prey by emitting sound waves that bounce off objects and return to the animal’s ears or other sensory organ.
Echosounder: A tool that bounces sound waves off the ocean floor to record water depths or create maps of the ocean floor.
Ecology: Study of the relationships among organisms and between organisms and their environment.
Ecosystem: Community of plants and animals that interact with each other and with their physical environment.
Ecotourism: Tourism that focuses on nature and the environment without harming it.
Ectotherm: An animal that has a body temperature similar to that of its environment.
Effluent: Wastewater that has been treated to remove most impurities.
Electrical current: Flow of electricity.
Electromagnetic spectrum: The range of electrical waves of varying wavelengths that make up light. The visible range is only a small portion of the full spectrum.
Electron: A particle with a negative charge that orbits the nucleus of an atom.
Element: A substance that cannot be divided by ordinary chemical means.
Embayment: Indentation in the shoreline that forms a bay.
Endangered: A species that is in danger of becoming extinct within the foreseeable future throughout all or a significant portion of its natural habitat.
Endangered Species Act: Law passed in 1973 that identifies species that face possible extinction and implements measures to prevent extinction; species may be listed as either endangered or threatened under the act.
Endotherm: An animal that can maintain a relatively constant body temperature regardless of its environment.
Endothermic: Chemical reaction or phase change that absorbs energy
Environmental impact study: A survey conducted to determine if a landfill project could have negative effects on the environment.
Environmental Protection Agency: Federal agency responsible for enforcing laws designed to protect the environment, including air quality, water quality, wetlands, hazardous wastes, and other environmental matters.
Epilimnion: The surface of a lake that extends as deep as light penetrates.
Epipelagic zone: The surface of the ocean where light penetrates; also called the photic zone.
Equatorial current: A sustained pattern of water flowing westward near the equator.
Erosion: Wearing away of soil, rock, sand, or other material by the action of wind and water.
Erosional coastline: A coastline formed by rising tectonic plates that gradually wears away.
Escherichia coli: Type of bacteria that is found in the intestines of warm-blooded animals including humans; some types can cause illness if ingested.
Estuary: Wide part of a river where it nears the sea; where fresh and salt water mix.
Eutrophic: Waters with a good supply of nutrients.
Eutrophication: Proliferation of plant life, especially algae, that results when excess nutrients are added to lake or pond water, which reduces the oxygen content and often causes the death of animals.
Evaporation: The change of liquid water to water vapor.
Exclusive economic zone: A 200-mile (322-kilometer) area extending from a nation’s coastline that permits that nation to extract resources such as oil, gas, and fish and to pass laws to protect those resources.
Exothermic: Chemical reaction or phase change that produces heat.
Export: Raw materials or goods that are shipped, traded, or sold to other nations.
Extinction: The total disappearance of a species; the irreversible loss of a living species.
Eye: Small circular area of relative calm at the center of a cyclone.
Ferry: Ship that transports cars and people across bodies of water on a regular schedule.
Filtration: The process by which pollutants are removed from water.
Fishing regulations: Restrictions placed on where, when, and how fish may be caught.
Fixed wave power device: Wave power electrical generator that is attached to the seafloor and/or shore.
Fjord: A long, narrow, deep glacial valley flooded by the sea.
Flash flood: Flood that rises and dissipates rapidly with little or no advance warning, usually as the result of intense rainfall over a relatively small area.
Floating wave power device: Wave power electrical generator that is floating in shallow water.
Floodplain: Flat land adjacent to rivers that are subject to flooding during periods of heavy rainfall.
Food chain: Relationship of organisms in an ecosystem in which each member species feeds on other species.
Food web: The predator and prey relationships between animals and plants.
Free diving: Underwater swimming without the use of a breathing apparatus; also known as skin diving or breath-hold diving.
Frond: A long, feathery leaf, or the blade of a kelp plant or sea plant.
Front: The boundary between two air masses of different temperature and humidity
Generator: Machine that converts mechanical energy to electrical energy.
Geothermal: Heat from Earth; energy obtained from the hot areas under the surface of the Earth.
Glacial erratic: Boulders carried by glaciers and deposited away from their original location.
Glacial flour: Sediments that have been crushed and ground into a fine texture beneath a glacier.
Glacial outwash: Sand and gravel deposited by water melting from a glacier.
Glacial till: Sediments, or the rock, gravel, and sand carried and deposited by a glacier.
Glacier: Large mass of moving ice.
Global warming: Increase in the average temperature of the Earth’s surface.
Gorge: A deep, narrow ravine, often with a river or stream running through it.
Graben: Rifts or holes formed when tectonic plates pull away from each other; when filled with water they can form large lakes.
Graded profile: A stream or river with a constant slope (incline).
Graded stream: A stream that has achieved a constant slope (profile) by reaching a balance of erosion and deposition.
Gravity: The natural force of attraction between any two objects that depends upon the mass of the objects and the distance between the objects. Planets, like Earth, draw objects toward their surfaces. Attraction is directly proportional to the product of the masses of the bodies and inversely proportional to the square of the distance between the bodies.
Gray water: Water that has been used for bathing, in the kitchen, or other purposes that do not generate highly-contaminated wastewater.
Greenhouse effect: The process where light from the Sun is reflected off Earth’s surfaces and then trapped by clouds to warm Earth’s atmosphere and surface.
Greenhouse gases: Gases in Earth atmosphere’s that include water vapor and carbon dioxide, methane, nitrous oxides, ozone, halogens (bromine, chlorine, and fluorine), halocar-bons, and other trace gases (gases found in very relatively small amounts).
Greenhouse layer: Layer of gases in the atmosphere that lets pass incoming solar rays and traps escaping heat.
Gross tons: A marine term equal to 100 cubic feet (about 10 cubic meters) used to describe the size of a boat, ship, or barge.
Groundwater: Freshwater that resides in rock and soil layers beneath Earth’s land surface.
Groyne: A wall-like structure that sticks out into the water from the beach, which is intended to trap material.
Guyot: A flat-topped submarine mountain.
Gyres: Large circular patterns created by surface water currents in the oceans.
Habitat: The environment in which a species naturally or normally lives and grows.
Hadal zone: The layer of the ocean in deep trenches and submarine canyons at depths that can extend down to 35,750 feet (11,000 meters).
Halite: A mineral composed of sodium chloride, commonly known as rock salt.
Halocline: Layer of water where the salinity changes rapidly with depth.
Headland: Point that extends into the ocean; usually a high rocky point surrounded by sea cliffs.
Heavy metal: Element such as lead or mercury that tends to be toxic to plant and animal life, even when present in a low concentration.
Heterotroph: Organism that consumes another organism to obtain energy.
Himalaya Mountains: Tall mountain range in central Asia that includes nine of the world’s ten highest peaks, including the tallest one, Mt. Everest.
Holdfast: The part of a seaweed that allows the plant to attach to a rock.
Holoplankton: Plankton that spend their entire life cycle floating and drifting among the currents.
Homeostasis: Tendency for a system to resist change.
Hovercraft: Ship that floats over the surface of the water on a cushion of air.
Humidity: Water vapor (moisture) in the air.
Hurricane: An organized storm (tropical cyclone) with sustained winds of 74 miles per hour (119 kilometers per hour) or greater in the Atlantic Ocean, Gulf of Mexico, Caribbean Sea, or eastern Pacific Ocean.
Hydrocarbon: Chemical substance made up of carbon and hydrogen; propane, gasoline, kerosene, diesel fuel, and lubricating oil are common hydrocarbons.
Hydrofoil: Ship that has wing-like foils under the hull of the ship that provide lift that raises the hull of the ship out of the water.
Hydrogeologist: Scientist who studies the properties and distribution of freshwater, especially as it relates to the soil and rock structure of the Earth.
Hydrologic potential: Potential energy in water stored in reservoirs above the elevation of a river downstream.
Hydrologist: Scientist who studies the properties and distribution of Earth’s freshwater.
Hydrophilic: Easily dissolvable in water.
Hydrophobic: Not easily dissolvable in water.
Hydrosphere: The whole body of water that exists on or around Earth, including water in the atmosphere, lakes, oceans, rivers, and groundwater.
Hydrothermal deposit: Mineral-containing geologic unit that was formed by hot waters percolating through source rocks.
Hydrothermal vents: Volcanic-powered, hot spring openings in the ocean floor that spew out a fluid that is rich in chemicals and minerals.
Hypolimnion: The deep part of a lake where no light penetrates.
Hypopycnal flow: River water that floats on top of sea water as it flows out to the ocean; it is caused by the fact that river water is less dense than salty sea water.
Hypothermia: Condition in which the body becomes too cold to function properly.
Hypoxia: Condition in which the concentration of oxygen in body tissues is too low for the body to function normally.
Ice budget: The total amount of frozen water on Earth.
Ice cap: Ice at the poles; large dome-shaped glaciers that are smaller than ice sheets.
Ice front: The ice at the lowest end of a glacier.
Ice sheet: Very large, dome-shaped mass of glacial ice that covers a large continental area; also called continental glacier.
Ice shelf: A floating platform of ice where an ice sheet flows out over water.
Ice stream: Portion of a glacier or ice sheet that flows faster than the surrounding ice.
Iceberg: Large chunk of ice that breaks off from glaciers and floats in the oceans.
Ichthyology: The scientific study of fish.
Import: Raw materials or goods that are produced in a foreign country and brought into another.
In situ: In place.
Industrial Revolution: Period of rapid industrial growth, usually dated from 1750 to 1900, that resulted in a shift from economies based on agriculture and small businesses to economies based on industry and large corporations.
Influent streams and ponds: Bodies of surface water in recharge zones that contribute groundwater.
Interdistributary: Land or water that is between distributaries in deltas.
Internal combustion engine: An engine that takes the energy in fuel and combusts (burns) it inside the engine to produce motion.
International Maritime Organization (IMO): International agency of the United Nations that is concerned with shipping regulation and safety.
International organization: A group that includes two or more countries and that operates in more than one country.
Intertidal: The zone of the seashore between the high tide point and the low tide point.
Inuit: The native human inhabitants of the Arctic coastal regions of Eastern Asia (Siberia), North America and Greenland; also known as Eskimo, although this term has fallen out of favor.
Invertebrate: An animal without a backbone.
Ion: An electrically charged atom or group of atoms.
Irrigation: Diverting freshwater from lakes and rivers for use in agriculture to provide water for crops.
