Oceanography Vocab Exam 1

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Abyssal Hill

Back 1

Small, sediment-covered, extinct volcanoes or intrusions of once-molten rock usually less than 200 meters high.

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Abyssal Plain

Back 2

Flat, featureless expanses of sediment-covered ocean floor found on the periphery of all oceans.

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Active Margin

Back 3

Continental margins near the edges of converging plates near places where plates are slipping past one another. Also Called Pacific-type margin.

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Big Bang

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The hypothetical event that started the expansion of the universe from a geometric point; the beginning of time.

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Basalt

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Relatively heavy crustal rock that forms the seabeds, composed mostly of oxygen, silicon, magnesiym, and iron.

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Body Wave

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A seismic wave that moves through the interior of the earth, as opposed to surface waves that travel near the earth's surface. Includes both P and S waves

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Chronometer

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A consistent clock. It doesn't need to tell accurate time, but its rate of gain or loss must be constant and known exactly so that accurate time may be calculated.

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Compass

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An instrument for showing direction by means of a magnetic needle swinging freely on a pivot and pointing to magnetic north.

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Condensation Theory

Back 9

Premise that stars and planets accumulate from contracting, accreting clouds of galactic gas, dust, and debris.

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Continental Crust

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The solid masses of the continents, composed primarily of granite.

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Continental Drift

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The theory that the continents move slowly across the surface of the Earth.

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Continental Margin

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The submerged outer edge of a continent, made of granitic crust; includes the continental shelf and slope.

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Continental Rise

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The wedge of sediment forming the gentle transition from outer (lower) edge of the continental slope to the abyssal plain; usually associated with passive margins

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Continental Shelf

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The gradually sloping submerged extension of a continent, composed of granitic rock overlain by sediments; has features similar to the edge of the nearby continent.

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Continental Slope

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The sloping transition between the granite of the continent and the basalt of the seabed; the true edge of a continent.

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Convection Current

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A single closed-flow circuit of rising warm material and falling cool material.

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Convergent Plate Boundary

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A region where plates are pushing together and where a mountain range, island arc, and/or trench will eventually form; often a site of much seismic and volcanic activity.

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Core

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The innermost layer of the earth, composed mostly of iron. (Inner-solid/outer-liquid)

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Crust

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The outermost solid layer of Earth, composed mostly of granite and basalt; the top of the lithosphere.

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Density Stratification

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The formation of layers in a material, with each deeper layer being denser than the layer above.

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Divergent Plate Boundary

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A region where plates are moving apart and where new ocean or rift valley will eventually form.

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Echo Sounder

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A device that reflects sound off the ocean bottom to sense water depth.

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Galaxy

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A large rotating aggregation of stars, dust, gas, and other debris held together by gravity.

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Granite

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The relatively light crustal rock-composed mainly of oxygen, silicone, and aluminum-that forms the continents.

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Guyot

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A flat-topped, submerged inactive volcano.

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Hypothesis

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A speculation about the natural world that may be verified or disproved by observation and experiment.

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Island Arc

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Curving chain of volcanic islands and seamounts almost always found paralleling the concave edge of a trench.

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Latitude

Back 28

Regularly spaced imaginary lines on Earth’s surface running parallel to the equator.

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Longitude

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Regularly spaced imaginary lines on Earth’s surface running north and south and converging at the poles.

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Mantle

Back 30

The layer of Earth between the crust and the core, composed of silicates of iron and magnesium.

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Nebula

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Diffuse cloud of dust and gas.

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Ocean Basin

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Deep-ocean floor made of basaltic crust.

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Oceanic Crust

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The outermost solid surface of Earth beneath ocean floor sediments, composed primarily of basalt.

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Oceanic Ridge

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Young seabed at the active spreading center of an ocean, often unmasked by sediment, bulging above the abyssal plain.

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Outgassing

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The volcanic venting of volatile substances.

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P Wave

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Primary wave; a compressional wave that is associated with an earthquake and that can move through both liquid and rock.

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Paleomagnetism

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The “fossil,” or remanent, magnetic field of a rock.

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Pangea

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Name given by Alfred Wegener to the original “protocontinent.”

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Panthalassa

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Name given by Alfred Wegener to the ocean surrounding Pangaea.

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Passive Margin

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The continental margin near an area of litospheric plate divergence; also called Atlantic-type margin.

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Planet

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A smaller, usually nonluminous body orbiting a star.

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Plate Tectonics

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The theory that Earth’s lithosphere is fractured into plates that move relative to each other and are driven by convection currents in the mantle

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Protostar

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A tightly condensed knot of material that has not yet attained fusion temperature.

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Radioactive Decay

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The disintegration of unstable forms of elments, which releases subatomic particles and heat.

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Radiometric Dating

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The process of determining the age of rocks by observing the ratio of unstable radioactive elements to stable decay products.

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S Wave

Back 46

Secondary wave; a transverse wave that is associated with an earthquake and that cannot move through liquid.

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Seafloor Spreading

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The theory that new ocean crust forms at spreading centers, most of which are on the ocean floor, and pushes the continents aside.

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Seamount

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A circular or elliptical projection from the sea floor.

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Seismic Wave

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A low-frequency wave generated by the forces that cause earthquakes.

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Shelf Break

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The abrupt increase in slope at the junction between continental shelf and continental slope.

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Solar System

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The sun togetherwith the planets and other bodies that revolve around it.

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Submarine Canyon

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A deep, V-shaped valley running roughly perpendicular to the shoreline and cutting across the edge of the continental shelf and slope.

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Subduction Zone

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An area at which a lithospheric plate is descending into the asthenosphere. The zone is characterized by linear folds (trenches) in the ocean floor and strong deep focus earthquakes

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Theory

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A general explanation of a characteristic of nature consistently supported by observation or experiment.

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Transform Fault

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A plane along which rock masses slide horizontally past one another.

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Transform Plate Boundary

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Places where crustal plates shear laterally past one another. Crust is neither produced nor destroyed at this type of junction.

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Trench

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An arc-shaped depression in the deep-ocean floor with very steep sides and a flat sediment-filled bottom coinciding with a subduction zone.

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Turbidity Current

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An underwater “avalanche” of abrasive sediments thought responsible for the deep sculpturing of submarine canyons and a means of transport for sediments accumulating on abyssal plains.

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Christopher Colombus

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Italian explorer in the service of Spain who discovered islands in the Caribbean in 1492. Although traditionally credited as the discoverer of America, he never actually sighted the North American continent.

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James Cook

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Officer in the British Royal Navy who led the fi rst European voyages of scientific discovery.

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Charles Darwin

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An English biologist and the co-discoverer (with Alfred Russell Wallace) of evolution by natural selection.

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Benjamin Franklin

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Published the first chart of an ocean current in 1769.

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John Harrison

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British clockmaker who invented the modern chronometer in 1760

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Ferdinand Magellan

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Portuguese navigator in the service of Spain who led the first expedition to circumnavigate Earth, 1519– 1522. He was killed in the Philippines.

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Matthew Maury

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“Father” of physical oceanography. Probably the first person to undertake the systematic study of the ocean as a full-time occupation, and probably the first to understand the global interlocking of currents, wind flow, and weather.

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Fridtjof Nansen

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Norwegian explorer who courageously allowed his specially designed ship 'Fram' to be trapped in the Arctic ice, where he and his crew of 13 drifted with the pack for nearly 4 years