Glossary

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algae: a diverse group of photosynthetic marine organisms that includes seaweeds.

aerobic: used to describe 1) an organism that can live only with free oxygen, or 2) an environment containing free oxygen.

anaerobic: used to describe 1) an organism that can live without free oxygen, or 2) an environment that contains no free oxygen.

anoxic: completely lacking free oxygen (O₂)

archaea: micro-organisms that belong to a major division of life, as different from bacteria as humans are.

asthenosphere: the layer in the Earth below the lithosphere that is weak, probably due to the presence of some molten material. It is this weak layer that allows the tectonic plates to move.

Austral: relating to or coming from the south, especially the southern hemisphere

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bacteria: a single-celled microorganism that lacks a nucleus

bathymetric map: a map of the bottom of the ocean, with water depths indicated by contours that join points of equal water depth

benthos: organisms that live on or in the sediments of the seafloor

biofilm: a thin, slimy mat of bacteria and chemicals they produce.

biomass: the organic material that makes up the body of a plant, animal, or other organism.

black smoker: a chimney-like structure on the seafloor made of metal sulfides, out of which hot (~350°C) fluids that look like black smoke flow. The black color of the fluid is due to mineral particles within it

brine: salty water

buoyancy: the tendency of a body or fluid to rise when it is less dense than its surroundings.

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carbohydrates: compounds composed of carbon, hydrogen and oxygen, including sugars and starches.

chemosynthesis: the process by which bacteria use energy from chemicals, such as hydrogen sulfide, to combine water and carbon dioxide to produce carbohydrates

climate: the accumulation of daily and seasonal weather events over a long period of time. The sum of all statistical weather information that helps describe a place or region.

cold seeps: A place on the seafloor where chemicals such as hydrocarbons and sulfides leak to the surface from below to support a variety of organisms.

consumer: organisms that get their energy from eating other

convection: the circulatory motion that occurs in fluids due to differences in temperature, which cause variations in density.

converging plate boundary: boundary along which two lithospheric plates are moving towards each other; e.g. the Himalayas are forming as two plates collide.

coral: colonial animal that secretes a hard outer calcareous (calcium carbonate) skeleton.

crust: the outermost shell of the Earth, made of different materials depending on whether it is oceanic or continental crust.

CTD (conductivity/temperature/depth): One of the most commonly used electronic instruments in oceanography, which is lowered on a conducting cable from a ship to measure the temperature, pressure and electrical conductivity of ocean water and the height above the seafloor. From these measurements, scientists can calculate water depth, salinity, and density. By letting cable out or pulling it in, scientists can measure water properties at different depths. Some CTDs have batteries and computers that allow them to be self-recording so they can be moored in one spot to make measurements for days or months.

cyanobacteria: an abundant type of bacteria that use photosynthesis to live and grow, but are also capable of converting nitrogen gas from the atmosphere into other forms of nitrogen that they and other organisms need to live and grow.

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detritus: non-living organic material that typically includes the bodies or fragments of dead organisms as well as fecal material

DHAB: Deep Hypersaline Anoxic Basin

dispersant: a chemical used to break up large concentrations of oil

diverging plate boundary: a boundary between two plates that are moving apart, where volcanic activity is creating new oceanic crust - the mid-oceaen ridge is an example.

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East Pacific Rise: a part of the mid-ocean ridge system running northeasterly from near New Zealand to just off the coast of Mexico in the Gulf of California. There is a lot of volcanic activity associated with this seafloor spreading center, as well as many hydrothermal vents.

earthquake: movement (shaking or sudden motion) of the Earth caused by the rapid release of strain.

ecology: the study of the relations between organisms and their environment.

ecosystem: a unit in ecology consisting of the community of organisms and the environment in which it lives.

enzymes: proteins that trigger or speed up specific biochemical reactions.

eukaryote: any organism whose cells contain a nucleus and membrane-bound organelles such as mitochondria; includes single-celled organisms such as protists and multicellular organisms such as plants and animals (including humans)

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food chain: a sequence of feeding relationships by which energy is transferred from primary producers to consumers.

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geophysics: a field of geology using the principles of physics to explore the structure and physical characteristics of the Earth

geyser: a type of hot spring seen on land that episodically erupts jets of hot water and steam. It results from ground water being heated by coming in contact with hot rock deep in the Earth's crust, and then rising to the surface.

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halocline: zone where the concentration of salt changes from high to low

halophile: organism that thrives in a high-salt environment

hydrogen sulfide: a colorless, poisonous gas with an odor of rotten eggs.

hydrothermal: pertaining to hot water.

hydrothermal deposit: a mineral deposit formed from precipitation of minerals from fluids.

hydrothermal plume: A cloud of hot, mineral-rich water that flows out of a hydrothermal vent and disperses into the ocean, usually several hundred meters above the seafloor vent site. Rock particles and minerals in the plume water often make the plume look smoky, like a cloud of ash over an erupting volcano.

hydrothermal system: a system of circulation of fluid caused by a heat source (often a magma chamber or hot rock) in which water flows into the crust in one area (the recharge zone) and out of the crust in another area (the discharge zone).

hypersaline: environment that has a very high concentration of salt

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igneous rock: a rock that solidified from molten or partly molten material, i.e. magma.

in situ: Latin phrase for “in place.” A procedure done in situ is done where the sample was collected, rather than back in the lab or on a ship.

island arc: series of volcanic islands that are built above a subduction zone.

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krill: shrimp-like planktonic crustaceans; an abundant and major food source for Antarctic animals such as whales, fish, and penguins.

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latitude: The angular distance north or south from the Earth’s equator, measured in degrees, minutes, and seconds. One degree equals 60 nautical miles. A combination of latitude and longitude can be used to locate any spot on the earth’s surface.

lava: Melted, or molten, rock is called magma if it is below the earth's surface, and lava if it reaches the earth's surface.

lithosphere: a strong layer of the Earth, about 100 km in thickness, consisting of the Earth's crust and a portion of the underlying upper mantle. This layer lies on top of the weaker asthenosphere.

longitude: The angular distance east or west from a meridian drawn between the North Pole to the South Pole and passing through Greenwich, England, measured in degrees, minutes, and seconds. A combination of latitude and longitude can be used to locate any spot on the Earth’s surface.

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mantle: the 2900 km thick zone of the Earth below the crust and above the mantle made up of minerals that contain iron, silica, magnesium and oxygen.

metabolic rate: a measure of how quickly an organism uses energy.

metal: an element, such as iron or copper, that are good conductors of heat and electricity, and have a characteristic luster.

metal sulfide: a mineral in which the element sulfur is linked with a metal, such as iron sulfide in the mineral pyrite, commonly known as fool's gold.

metamorphic rock: a rock derived from a pre-existing rock that has been changed in its minerals, chemistry and structure in response to changes in temperature, pressure and stress.

metazoan: any multicellular organism.

microbe: a microscopically visible organism in the size range of 1/100 to 1/1000 millimeter, mostly consisting of only a single cell. Individual Bacteria and Archaea are microbes.

mid-ocean ridge system: The volcanic mountain chain that is formed by volcanic activity at the boundary between two tectonic plates that are drifting apart. Molten rock from the mantle below rises to the surface and solidifies to form new oceanic crust.

mineral deposit: Accumulation of naturally occurring minerals.

mutualism: the form of symbiosis in which both participants benefit

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organelle: structure, located inside a cell, that has a specific function and is surrounded by a membrane. Examples are mitochondria and Golgi apparatus.

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photosynthesis: The process by which green plants use energy from the sun to combine water and carbon dioxide to produce carbohydrates and oxygen.

phytoplankton: small or microscopic photosynthetic organisms that float or drift in great numbers in fresh or salt water near the surface and are the base of the ocean food chain

pillow lava: lava that erupts under water and forms rocks that display a typical rounded, pillow shape.

plate: a rigid piece of the Earth's lithosphere that moves horizontally and interacts with other plates along its boundaries.

plate boundary: zones of seismic and tectonic activity along the edges of lithospheric plates.

plate tectonics: the idea that the Earth's lithosphere can be divided into a number of plates that move and interact with each other along their boundaries.

primary producers: living things that produce their own food (e.g., bacteria and plants).

prokaryote: single-celled organism that lacks a nucleus and membrane-bound organelles. Includes bacteria and archaea.

protist: mostly single-celled eukaryotic organism. It has a nucleus and organelles. Examples include Amoeba, Paramecium, and Trypanosoma.

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radiocarbon dating: a method of dating material that contains the element carbon. The method uses isotopes of carbon, and can determine the age of materials as old as 70,000 years.

redox reaction: short for “reduction-oxidation.” A chemical reaction involving the exchange of electrons between two atoms or molecules, releasing energy in the process.

remote sensing: way of getting information about an object without having the measuring device in direct contact with it. Examples include radar’s use of radio waves and sonar’s use of sound waves to detect objects.

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salinity: A measure of dissolved salts in sea water. It is calculated as the amount of salt (in grams) dissolved in 1,000 grams (1 kilogram) of seawater.

salps: transparent, barrel-shaped planktonic marine animals found singly or in chains that sometimes reach 20 feet in length

seafloor speading: area where two tectonic plates are moving apart (diverging), opening the seafloor and allowing magma to rise and form new oceanic crust.

seamount: an extinct, underwater volcano that rises more than 1 km above the seafloor but whose peak is below the sea surface.

sediment trap: an oceanographic instrument used to collect material floating down to the seafloor from above

sedimentary rock: a rock formed from the consolidation

seep: A small area where water – that may be of a different temperature and density flows from below the seafloor and rises slowly into the ocean.

seismic wave: waves generated either by an earthquake or artificially.

sonar: acronym for sound navigation and ranging. A device that is used primarily for the detection and location of underwater objects by reflecting acoustic (sound) waves from them.

subduction zone: the region where one lithospheric plate descends beneath another as the two plates are moving towards each other. It is characterized by a line of earthquakes that demarcate the upper edge of the descending plate.

symbiosis: close physiological relationship between two different organisms for the majority of their life cycles. If the relationship benefits both organisms, it is called mutualism. If one organism benefits at the expense of the other, it is called parasitism. If one organism benefits and the other is neither helped nor harmed, it is called commensalism.

symbiotic algae: algae (a simple type of plant that can photosynthesize) that live together with another organism in a mutually beneficial relationship.

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tectonics: a field of geology dealing with processes that shape the Earth's surface.

transform fault: a type of plate boundary where two plates slide past each other.

transponder: An acoustic device that scientists place above the seafloor, usually in groups of two or more, to help them navigate deep submergence vehicles. To locate a transponder, a ping is broadcast from a ship to the seafloor. If the transponder hears the ping, it sends a reply ping, letting researchers know they’re in the right place. The transponder and its batteries are protected inside a plastic case the size of a beach ball, and can operate from the seafloor for up to five years.

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uranium-series dating: a method of dating material that contains elements that have been formed by radioactive decay of uranium.

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volcanic eruption: ejection of hot steam, molten rock, and/or rock fragments through openings in the earth's surface.

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water mass: a body of seawater that shares the same origin. Each water mass has characteristic temperatures and salinities.

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zooplankton: small or microscopic animals that float or drift in great numbers in fresh or salt water near the surface and are the base of the ocean food chain.

Credit: Tasa Graphic Arts, Inc.
Tasa Graphic Arts, Inc. has been illustrating college textbooks since 1978, specializing in the area of geology and geography. In 1993 they began producing earth science educational computer software on CD-ROM.