Oceanography vocab quiz #1 - ch 1, 3, 4

abyssal hill

Small, sediment-covered, inactive volcano or intrusion of molten rock less than 200 meters (650 ft) high, thought to be associated with seafloor spreading. Abyssal hills punctuate the otherwise flat abyssal plain.

abyssal plain

Flat, cold, sediment-covered ocean floor between the continental rise and the oceanic ridge at a depth of 3700 to 5500 meters (12,000-18,000 feet). Abyssal plains are more extensive in the Atlantic and Indian oceans than in the Pacific

active continental margin (active margin)

The Continental margin near an area of lithospheric plate convergence; also called Pacific-type margin.

big bang

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

basalt

The relatively heavy crustal rock that forms the seabeds, composed mostly of oxygen, silicon, magnesium, and iron. Its density is about 2.9 g/cm³

body wave

Seismic waves that travel through Earth’s interior; see P wave and S wave.

condensation theory

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

continental crust

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

continental drift

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

continental margin

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

continental rise

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

continental shelf

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

continental slope

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

convection current

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

convergent plate boundary

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

core

the innermost layer of Earth, composed primarily of iron, with nickel and heavy elements. The inner core is thought to be a solid 6000°C (11,000°F) sphere, the outer core a 5000°C (9000°F) liquid mass. The average density of the outer core is about 11.8g/cm³, and that of the inner core is about 16g/cm³

crust

The outermost solid layer of Earth, composed mostly of granite and basalt; the top of the lithosphere. The crust has a density of 2.7 to 2.9g/cm³ and accounts for 0.4% of Earth’s mass.

density stratification

the formation of layers in a material, with each deeper layer being denser (weighing more per unit of volume) than the layer above

Robert Dietz

Along with Harry Hess, proposed the hypothesis of sea floor spreading. Evidence they gathered from military research suggested that 1) oceanic crust was youngest at oceanic ridge crests and older toward continents, and 2) high heat flow at oceanic ridge crests

divergent plate boundary

A region where plates are moving apart and where new ocean of rift valley will eventually form. A spreading center forms the junction.

epicenter

galaxy

A large, rotating aggregation of stars, dust, gas, and other debris held together by gravity. There are perhaps 50 billion galaxies in the universe and 50 billion stars in each galaxy.

granite

The relatively light crustal rock - composed mainly of oxygen, silicon, and aluminum - that forms the continents. Its density is about 2.7g/cm³.

guyot

A flat-topped, submerged, inactive volcano

Harry Hess

Along with Robert Dietz, proposed the hypothesis of sea floor spreading. Evidence they gathered from military research suggested that 1) oceanic crust was youngest at oceanic ridge crests and older toward continents, and 2) high heat flow at oceanic ridge crests

island arc

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

lithosphere

The brittle, relatively cool outer layer of Earth, consisting of the oceanic and continental crust, and the outermost, rigid layer of the mantle.

mantle

The layer of Earth between the crust and the core, composed of silicates of iron and magnesium. The mantle has an average density of about 4.5g/cm³ and accounts for about 68% of Earth’s mass.

nebula

Diffuse cloud of dust and gas (plural = nebulae)

ocean basin

Deep-ocean floor made of basaltic crust. Compare Continental margin.

oceanic crust

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

oceanic ridge

Young seabed at the active spreading center of an ocean, often unmasked by sediment, bulging above the abyssal plain. The boundary between diverging plates. Often called a mid-ocean ridge, though less than 60% of the length exists at mid-ocean.

outgassing

The volcanic venting of volatile substances

P wave (primary wave)

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

paleomagnetism

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

Pangaea

Name given by Alfred Wegener to the original “protocontinent.” The breakup of Pangaea gave rise to the Atlantic Ocean and to the continents we see today.

Panthalassa

Name given by Alfred Wegener to the ocean surrounding Pangaea.

passive continental margin

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

planet

A smaller, usually non luminous body orbiting a star.

plate tectonics

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. Most volcanic and seismic activity occurs at plate margins.

protostar

The first step in forming a star is that a nebula (interstellar cloud of gas and dust) contracts to form a protostar.

At this stage, all the material needed to create a star is concentrated but temperatures are still not high enough for nuclear fusion to begin. 

radioactive decay

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

radiometric dating

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

S wave (secondary wave)

A transverse wave that is associated with an earthquake and that cannot move through liquid.

seafloor spreading

The theory that new ocean crust forms at spreading centers, most of which are on the ocean floor, and pushes the continents aside. Power is thought to be provided by convection currents in Earth’s upper mantle.

seamount

A circular or elliptical projection from the seafloor, more than 1 kilometer (0.6 mile) in height, with a relatively steep slope of 20° to 25°.

seismic wave

A low-frequency wave generated by the forces that cause earthquakes. Some kinds of seismic waves can pass through Earth. See also P wave; S wave

shelf break

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

Solar system

The Sun together with the planets and other bodies that revolve around it.

Subduction zone

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; also called a Wadati-Benioff zone.

Transform fault

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

Transform plate boundary

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

Trench

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

Turbidity current

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

Alfred Wegener

(1880-1930) German scientist who proposed the theory of continental drift in 1912.