Chapter 02 Vocab Flashcards

1
Q

absolute plate velocity

A

The movement of a plate relative to a fixed point in the mantle.

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2
Q

abyssal plain

A

A broad, relatively flat region of the ocean that lies at least 4.5 km below sea level.

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3
Q

accretionary prism

A

A wedge-shaped mass of sediment and rock scraped off the top of a downgoing plate and accreted onto the overriding plate at a convergent plate margin.

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4
Q

active margin

A

A continental margin that coincides with a plate boundary.

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5
Q

apparent polar-wander path

A

A path on the globe along which a magnetic pole appears to have wandered over time; in fact, the continents drift, while the magnetic pole stays fairly fixed.

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6
Q

asthenosphere

A

The layer of the mantle that lies between 100-150 km and 350 km deep; the asthenosphere is relatively soft and can flow when acted on by force.

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7
Q

bathymetry

A

Variation in depth.

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8
Q

black smoke

A

The cloud of suspended minerals formed where hot water spews out of a vent along a mid-ocean ridge; the dissolved sulfide components of the hot water instantly precipitate when the water mixes with seawater and cools.

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9
Q

collision

A

The process of two buoyant pieces of lithosphere converging and squashing together.

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10
Q

continental drift

A

The idea that continents have moved and are still moving slowly across the Earth’s surface.

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11
Q

continental rift

A

A linear belt along which continental lithosphere stretches and pulls apart.

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12
Q

continental shelf

A

A broad, shallowly submerged fringe of a continent; ocean-water depth over the continental shelf is generally less than 200 meters; the widest continental shelves occur over passive margins.

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13
Q

convergent boundary

A

A boundary at which two plates move toward each other so that one plate sinks (subducts) beneath the other; only oceanic lithosphere can subduct.

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14
Q

divergent boundary

A

A boundary at which two lithosphere plates move apart from each other; they are marked by mid-ocean ridges.

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15
Q

fracture zone

A

A narrow band of vertical fractures in the ocean floor; fracture zones lie roughly at right angles to a mid-ocean ridge, and the actively slipping part of a fracture zone is a transform fault.

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16
Q

global positioning system (GPS)

A

A satellite system people can use to measure rates of movement of the Earth’s crust relative to one another, or simply to locate their position on the Earth’s surface.

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17
Q

hot spot

A

A location at the base of the lithosphere, at the top of a mantle plume, where temperatures can cause melting.

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18
Q

hot-spot track

A

A chain of now-dead volcanoes transported off the hot spot by the movement of a lithosphere plate.

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19
Q

lithosphere

A

The relatively rigid, nonflowable, outer 100- to 150-km-thick layer of the Earth, constituting the crust and the top part of the mantle.

20
Q

magnetic anomaly

A

The difference between the expected strength of the Earth’s magnetic field at a certain location and the actual measured strength of the field at that location.

21
Q

magnetic declination

A

The angle between the direction a compass needle points at a given location and the direction of true north.

22
Q

magnetic dipole

A

An imaginary vector that points from the north magnetic pole to the south magnetic pole of a magnetic field.

23
Q

magnetic inclination

A

The angle between a magnetic needle free to pivot on a horizontal axis and a horizontal plane parallel to the Earth’s surface.

24
Q

magnetic pole

A

The ends of a magnetic dipole; all magnetic dipoles have a north pole and a south pole.

25
Q

magnetic-reversal chronology

A

The history of magnetic reversals through geologic time.

26
Q

magnetic reversal

A

The change of the Earth’s magnetic polarity; when a reversal occurs, the field flips from normal to reversed polarity, or vice versa.

27
Q

mantle plume

A

A column of very hot rock rising up through the mantle.

28
Q

mid-ocean ridge

A

A 2-km-high submarine mountain belt that forms along a divergent oceanic plate boundary.

29
Q

paleomagnetism

A

The record of ancient magnetism preserved in rock.

30
Q

paleopole

A

The supposed position of the Earth’s magnetic pole in the past, with respect to a particular continent.

31
Q

Pangaea

A

A supercontinent that assembled at the end of the Paleozoic Era.

32
Q

passive margin

A

A continental margin that is not a plate boundary.

33
Q

plate boundary

A

The border between two adjacent litho sphere plates.

34
Q

plate tectonics

A

The theory that the outer layer of the Earth (the lithosphere) consists of separate plates that move with respect to one another.

35
Q

relative plate velocity

A

The movement of one litho sphere plate with respect to another.

36
Q

rifting

A

The process by which a continent stretches and splits along a belt; if it is successful, rifting separates a larger continent into two smaller continents separated by a divergent boundary.

37
Q

sea-floor spreading

A

The gradual widening of an ocean basin as new oceanic crust forms at a mid-ocean ridge axis and then moves away from the axis.

38
Q

seamount

A

An isolated submarine mountain

39
Q

slab-pull force

A

The force that downgoing plates (or slabs) apply to oceanic lithosphere at a convergent margin.

40
Q

spreading rate

A

The rate at which sea floor moves away from a mid-ocean ridge axis, as measured with respect to the sea floor on the opposite side of the axis.

41
Q

subduction

A

The process by which one oceanic plate bends and sinks down into the asthenosphere beneath another plate.

42
Q

transform boundary

A

A boundary at which one litho sphere plate slips laterally past another.

43
Q

trench

A

A deep, elongate trough bordering a volcanic arc; a trench defines the trace of a convergent plate boundary.

44
Q

triple junction

A

A point where three lithosphere plate boundaries intersect.

45
Q

volcanic arc

A

A curving chain of active volcanoes formed adjacent to a convergent plate boundary.

46
Q

Wadati-Benioff zone

A

A sloping band of seismicity defined by intermediate- and deep-focus earthquakes that occur in the downgoing slab of a convergent plate boundary.