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Earth 201 > Ch 2: Plate Tectonics: Scientific Revolution Unfolds > Flashcards

Ch 2: Plate Tectonics: Scientific Revolution Unfolds Flashcards

1
Q

Asthenosphere

A

A subdivision of the mantle situated below the lithosphere. This zone of weak material exists below a depth of about 100 kilometers (60 miles) and in some regions extends as deep as 700 kilometers (430 miles). The rock within this zone is easily deformed.

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2
Q

Bar

A

Common term for sand and gravel deposits in a stream channel.

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3
Q

Basalt

A

A fine-grained igneous rock of mafic composition.

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4
Q

Basin

A

A circular downfolded structure.

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5
Q

Climate

A

A description of aggregate weather conditions; the sum of all statistical weather information that helps describe a place or region.

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6
Q

Continental drift

A

A hypothesis, credited largely to Alfred Wegener, which suggested that all present continents once existed as a single supercontinent. Further, beginning about 200 million years ago, the supercontinent began breaking into smaller continents, which then “drifted” to their present positions.

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7
Q

Continental rift

A

A linear zone along which continental lithosphere stretches and pulls apart. Its creation may mark the beginning of a new ocean basin.

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8
Q

Continental shelf

A

The gently sloping submerged portion of the continental margin, extending from the shoreline to the continental slope.

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9
Q

Continental volcanic arc

A

Mountains formed in part by igneous activity associated with the subduction of oceanic lithosphere beneath a continent. Examples include the Andes and the Cascades.

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10
Q

Convection

A

The transfer of heat by the mass movement or circulation of a substance.

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11
Q

Convergent plate boundary

A

A boundary in which two plates move together, resulting in oceanic lithosphere being thrust beneath an overriding plate, eventually to be reabsorbed into the mantle. It can also involve the collision of two continental plates to create a mountain system.

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12
Q

Core

A

The innermost layer of Earth. It is thought to be largely an iron–nickel alloy, with minor amounts of oxygen, silicon, and sulfur.

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13
Q

Crust

A

The very thin, outermost layer of Earth.

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14
Q

Curie point

A

The temperature above which a material loses its magnetization.

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15
Q

Density

A

A property of matter defined as mass per unit volume.

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16
Q

Divergent plate boundary

A

A boundary in which two plates move apart, resulting in upwelling of material from the mantle to create new seafloor.

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17
Q

Era

A

A major division on the geologic time scale; eras are divided into shorter units called periods.

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18
Q

Fault

A

A break in a rock mass along which movement has occurred.

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19
Q

Flow

A

A type of movement common to mass-wasting processes in which water-saturated material moves downslope as a viscous fluid.

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20
Q

Fossil

A

The remains or traces of organisms preserved from the geologic past.

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21
Q

Fossil magnetism

A

See Paleomagnetism.

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22
Q

Fracture

A

Any break or rupture in rock along which no appreciable movement has taken place.

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23
Q

Fracture zone

A

A linear zone of irregular topography on the deep-ocean floor that follows transform faults and their inactive extensions.

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24
Q

Glacier

A

A thick mass of ice originating on land from the compaction and recrystallization of snow that shows evidence of past or present flow.

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25
Q

Glass (volcanic)

A

Natural glass that is produced when molten lava cools too rapidly to permit recrystallization. Volcanic glass is a solid composed of unordered atoms.

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26
Q

Hot spot

A

A concentration of heat in the mantle, capable of producing magma that, in turn, extrudes onto Earth’s surface. The intraplate volcanism that produced the Hawaiian Islands is one example.

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27
Q

Hot spot tracks

A

A chain of volcanic structures produced as a lithospheric plate moves over a mantle plume.

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28
Q

Hypothesis

A

A tentative explanation that is then tested to determine if it is valid.

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29
Q

Ice sheet

A

A very large, thick mass of glacial ice flowing outward in all directions from one or more accumulation centers.

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30
Q

Intensity (earthquake)

A

A measure of the degree of earthquake shaking at a given locale, based on the amount of damage.

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31
Q

Lava

A

Magma that reaches Earth’s surface.

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32
Q

Lithosphere

A

The rigid outer layer of Earth, including the crust and upper mantle.

33
Q

Lithospheric plate (or Plate)

A

A coherent unit of Earth’s rigid outer layer that includes the crust and upper unit.

34
Q

Lower mantle

A

See Mesosphere

35
Q

Magnetic field

A

A phenomenon occurring around a magnet or an electric charge, characterized by a magnetic force at every point in the region. Earth’s magnetic field is dipolar and extends from the core out to the solar wind.

36
Q

Magnetic reversal

A

A change in Earth’s magnetic field from normal to reverse or vice versa.

37
Q

Magnetic time scale

A

A scale that shows the ages of magnetic reversals and is based on the polarity of lava flows of various ages.

38
Q

Magnetometer

A

A sensitive instrument used to measure the intensity of Earth’s magnetic field at various points.

39
Q

Mantle

A

One of Earth’s compositional layers. The solid rocky shell that extends from the base of the crust to a depth of 2900 kilometers (1800 miles).

40
Q

Mantle plume

A

A mass of hotter-than-typical mantle material that ascends toward the surface, where it may lead to igneous activity. These plumes of solid yet mobile material may originate as deep as the core– mantle boundary.

41
Q

Melt

A

The liquid portion of magma excluding the solid crystals.

42
Q

Mesozoic era

A

A time span on the geologic time scale between the Paleozoic and Cenozoic eras—from about 248 to 65.5 million years ago.

43
Q

Mid-ocean ridge (or Oceanic ridge)

A

A continuous mountainous ridge on the floor of all the major ocean basins and varying in width from 500 to 5000 kilometers (300 to 3000 miles). The rifts at the crests of these ridges represent divergent plate boundaries.

44
Q

Mineral

A

A naturally occurring, inorganic crystalline material with a unique chemical structure.

45
Q

Mountain belt

A

A geographic area of roughly parallel and geologically connected mountain ranges developed as a result of plate tectonics.

46
Q

Normal polarity

A

A magnetic field the same as that which presently exists.

47
Q

Ocean basin

A

A deep submarine region that lies beyond the continental margins.

48
Q

Oceanic ridge system

A

A continuous elevated zone on the floor of all the major ocean basins and varying in width from 500 to 5000 kilometers (300–3000 miles). The rifts at the crests of ridges represent divergent plate boundaries.

49
Q

Paleomagnetism

A

The natural remnant magnetism in rock bodies. The permanent magnetization acquired by rock that can be used to determine the location of the magnetic poles and the latitude of the rock at the time it became magnetized.

50
Q

Pangaea

A

The proposed supercontinent that 200 million years ago began to break apart and form the present landmasses.

51
Q

Plate resistance

A

A force that counteracts plate motion as a subducting plate scrapes against an overriding plate.

52
Q

Plate tectonics

A

A theory which proposes that Earth’s outer shell consists of individual plates that interact in various ways and thereby produce earthquakes, volcanoes, mountains, and the crust itself.

53
Q

Radiometric dating

A

The procedure of calculating the absolute ages of rocks and minerals that contain certain radioactive isotopes.

54
Q

Reverse polarity

A

A magnetic field opposite that which presently exists.

55
Q

Ridge push

A

A mechanism that may contribute to plate motion. It involves the oceanic lithosphere sliding down the oceanic ridge under the pull of gravity.

56
Q

Rift valley

A

A long, narrow trough bounded by normal faults. It represents a region where divergence is taking place.

57
Q

Seafloor spreading

A

A hypothesis, first proposed in the 1960s by Harry Hess, which suggested that new oceanic crust is produced at the crests of mid-ocean ridges, which are the sites of divergence.

58
Q

Seamount

A

An isolated volcanic peak that rises at least 1000 meters (3300 feet) above the deep-ocean floor.

59
Q

Sediment

A

Unconsolidated particles created by the weathering and erosion of rock by chemical precipitation from solution in water, or from the secretions of organisms, and transported by water, wind, or glaciers.

60
Q

Sheeting

A

A mechanical weathering process that is characterized by the splitting off of slablike sheets of rock.

61
Q

Shield

A

A large, relatively flat expanse of ancient igneous and metamorphic rocks within the craton.

62
Q

Shield volcano

A

A broad, gently sloping volcano built from fluid basaltic lavas.

63
Q

Shoreline

A

The line that marks the contact between land and sea. It migrates up and down as the tide rises and falls.

64
Q

Slab pull

A

A mechanism that contributes to plate motion in which cool, dense oceanic crust sinks into the mantle and “pulls” the trailing lithosphere along.

65
Q

Spreading center

A

See Divergent plate boundary.

66
Q

Striations (glacial)

A

Scratches or grooves in a bedrock surface caused by the grinding action of a glacier and its load of sediment.

67
Q

Subduction

A

The process by which oceanic lithosphere plunges into the mantle along a convergent zone.

68
Q

Subduction zone

A

A long, narrow zone where one lithospheric plate descends beneath another.

69
Q

Supercontinent

A

A large landmass that contains all, or nearly all, of the existing continents.

70
Q

Tectonics

A

The study of the large-scale processes that collectively deform Earth’s crust.

71
Q

Theory

A

A well-tested and widely accepted view that explains certain observable facts.

72
Q

Transform fault

A

A major strike-slip fault that cuts through the lithosphere and accommodates motion between two plates.

73
Q

Trigger

A

A factor or event, such as soil saturation, oversteepened slopes, removal of vegetation, or ground shaking, that initiates downslope movement of rock material.

74
Q

Upper mantle

A

The top portion of the mantle extending from the Moho to a depth of about 660 km and comprising the lithospheric mantle, asthenosphere, and transition zone.

75
Q

Volcanic

A

Pertaining to the activities, structures, or rock types of a volcano.

76
Q

Volcanic island

A

A seamount that has grown large enough to rise above sea level.

77
Q

Volcanic island arc

A

A chain of volcanic islands generally located a few hundred kilometers from a trench where there is active subduction of one oceanic plate beneath another.

78
Q

Volcano

A

A mountain formed from lava and/or pyroclastics.

Earth 201 (9 decks)

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