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Earth Science Unit 2 > Chapter 5 > Flashcards

Chapter 5 Flashcards

1
Q

Sir Francis Bacon

A

noted that shorelines of the Americas “fit” those of Africa and Europe (late 1600s, early 1700s)

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2
Q

Antonio Snider-Pellegrini

A
  • proposed that all continents were once connected but catastrophically separated in the past
  • thought the mechanism by which this occurred was Noah’s flood
  • published book in 1859
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3
Q

Alfred Wegener

A
  • meteorologist and geophysicist
  • studied glaciers
  • continental drift
  • Pangaea
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4
Q

Continental drift

A
  • 1915

- slow and gradual movement of continent over eons and eons of time

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5
Q

scientific revolution

A

profound reversal of ideas

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6
Q

Pangaea

A

“all land” -for a supercontinent whose breakup results in all current continents

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7
Q

Wegener’s Lines of Evidence

A
  • “Fit” of continents
  • matching geology of continents
  • fossil distribution
  • living organisms distribution
  • ancient climate
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8
Q

fit of continents evidence

A

especially South America and Africa

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9
Q

matching geology of continents evidence

A

especially with mountain chains

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10
Q

fossil distribution

A

-similar fossils found on continents now separated by oceans

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11
Q

good candidates for fossils

A

-terrestrian-meosaurus (reptile) and glossopteris (plant)

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12
Q

living organisms distribution

A

-marsupials in South America and Australia

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13
Q

ancient climate

A

evidence of glaciers in rock record at places that today could not make/sustain glaciers

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14
Q

Sir Edward Bullard and 2 associates constructed a map that what?

A

pieced together the edges of the continental shelves of South America and Africa at depths of 900 meters

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15
Q

glossopteris fossils were found where?

A

-Africa, Australia, India, South America, and Antarctica

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16
Q

when did Wegener’s proposal attract criticism?

A

1924 when it was translated into English, French, Spanish and Russian

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17
Q

main problem with continental drift

A

no mechanism to move the continents-doesn’t explain Rocky Mountains. in all only explains 1/3 of geology

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18
Q

1960s

A

declassified Navy data seafloor

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19
Q

big discovery

A

mid-ocean ridge

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20
Q

how was mid-ocean ridge discovered?

A

sonar

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21
Q

dredging of ocean floor revealed 2 patterns

A

1) sediments were thickest near continent and thiner near mid-ocean ridge
2) sediments near continents were young and old types, but those near the mid-ocean ridge were only young

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22
Q

seafloor spreading

A

occurs at the mid-ocean ridge (divergent boundary)

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23
Q

lithosphere

A

uppermost mantle and crust behave as a strong rigid layer

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24
Q

plates

A

segments of lithosphere

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25
Q

where is lithosphere thinnest?

A

oceans

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26
Q

asthenosphere

A

weak region in mantle underneath lithosphere

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27
Q

tectonic plates

A
  • aka lithospheric plates
  • 20 segments
  • in constant motion with respect to one another
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28
Q

largest plate

A

Pacific plate

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29
Q

plates that account for 94% of Earth’s surface area

A

North American, South American, Pacific, Eurasian, Australian-Indian, Antarctic

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30
Q

as plates move the distance between 2 locations on different plates ____ _____ whereas the distance between sites on the same plate remains ____ _____.

A

gradually changes; relatively constant

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31
Q

most major interactions among plates occurs on their

A

boundaries

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32
Q

plate tectonics=

A

continental drift + seafloor spreading

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33
Q

The earth’s surface is composed of

A

mobile plates (lithosphere)

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34
Q

divergent boundaries

A
  • aka constructive plate margins
  • aka spreading centers
  • where new crust is made
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35
Q

2 locations divergent boundaries are prominent

A

1) Mid-ocean ridges

2) Continental Rift Valley

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36
Q

example of continental rift valley

A

east african rift

37
Q

oceanic ridges

A

elevated areas of the seafloor that are characterized by high heat flow and volcanism

38
Q

how much of earth’s surface do oceanic ridges account for?

A

20%

39
Q

seafloor spreading

A

the mechanism that operates along the oceanic ridge to create new seafloor

40
Q

primary reason for elevated position of oceanic ridge

A

newly created oceanic crust is hot, making it less dense than cooler rocks found away from the ridge axis

41
Q

cooling ___ hot material directly below oceanic crust, adding to plate’s _____

A

strengthens, thickness

42
Q

continental rifting occurs where

A

opposing tectonic forces act to pull lithosphere apart

43
Q

convergent boundaries

A
  • aka destructive plate margins

- aka subduction zones

44
Q

oceanic lithosphere is ____ ____ than the athenosphere

A

more dense

45
Q

continental lithosphere is ___ ___ and resists _______

A

less dense, subduction

46
Q

deep ocean trenches

A

surface manifestations produced as oceanic lithosphere descends into the mantle

47
Q

angle at which oceanic lithosphere descends depends on its

A

density

48
Q

as oceanic lithosphere ages, it

A

thickens and increases in density

49
Q

oceanic-continental convergence

A

leading edge of plate caped with continental crust converges with a slab of oceanic lithosphere

50
Q

sediments and oceanic crust contain a large amount of

A

water that is carried to great depths by a subducting plate

51
Q

partial melting

A

the wedge of mantle rock is sufficiently hot that the introduction of water from the slab below leads to some melting

52
Q

examples of oceanic-continental convergence

A

South America (Andes), Pacific NW (Cascade Mountains)

53
Q

oceanic-oceanic convergence

A

2 oceanic slabs converge, one descends beneath the other, initiating volcanic activity by the same mechanism that operates at all subduction zones

54
Q

examples of oceanic-oceanic convergence

A

Japan, Philippines, Middle Earth

55
Q

continental-continental convergence

A

one landmass moves toward the margin of another because of subduction of the intervening seafloor

56
Q

examples of continental-continental convergence

A

Himalayan, past Appalachians

57
Q

subduction

A

sinking of ocean crust into the mantle

58
Q

transform boundaries

A
  • aka fault boundaries
  • plates slide past one another
  • near MOR’s
59
Q

ex. transform boundaries

A

San Andreas Fault

60
Q

fracture zones

A

include active and inactive transform faults

61
Q

where do active transform faults lie?

A

between 2 offset ridge segments, defined by weak, shallow earth quakes

62
Q

transform faults provide

A

means by which oceanic crust created at ridge crests can be transported to a site of destruction

63
Q

hot spots

A

a stationary plume of magma sourced from the lower mantle. Plates move over top of the hot spot.

64
Q

examples of hot spots

A

Hawaii and Yellowstone National Park

65
Q

new plate boundaries can be created or destroyed in response to

A

changes in the forces acting on the lithosphere

66
Q

mantle plume

A

cylindrically shaped upwelling of hot rock (like beneath island of Hawaii)

67
Q

hot-spot track

A

a chain of volcanic structures

68
Q

paleomagnetism

A

the record of Earth’s magnetic field as known via rocks

-helps settle out polar wander and magnetic

69
Q

some naturally occuring minerals are magnetic and hence

A

are influenced by Earth’s magnetic field (ex. magnetite which is abundant in lava flows of basaltic composition)

70
Q

Curie point

A

threshold for magnetism

71
Q

polar wandering

A

idea that magnetic poles migrated

72
Q

If the magnetic poles remain stationary, their apparent movement is produced by

A

continental drift

73
Q

normal polarity

A

when rocks exhibit the smae magnetism as the present magnetic field

74
Q

reverse polarity

A

when rocks exhibit the opposite magnetism are said to have reverse polarity

75
Q

chrons

A

major divisions of magnetic time scale

76
Q

magnetometers

A

used to do magnetic surveys of the ocean floor

77
Q

high-intensity magnetism

A

regions where paleomagnetism of the ocean crust exhibits normal polarity that enhance Earth’s magnetic field

78
Q

low-intensity magnetism

A

regions where the ocean crust is polarized in the reverse direction and weaken the magnetic field

79
Q

simplest type of convection

A
  • analogous to heating a pot of water on a stove
  • heating base causes material to rise in thin sheets that spread out at the surface and cool
  • surface layer thickens and sinks to bottom until it reheats again
80
Q

mantle convection

A
  • more complex than simple convection
  • mantle shape is spherical with a larger upper boundary than lower boundary
  • driven by combination of 3 thermal processes
81
Q

3 thermal processes that drive mantle convection

A

1-heating at the bottom by heat loss from Earth’s core
2-heating from within by decay of radioactive isotopes
3-cooling from the top that creates thick, cold lithospheric slabs that sink into the mantle

82
Q

what researchers agree on concerning convection

A

1-connective flow in the rocky mantle is the underlying driving force for plate movement
2-mantle convection and plate tectonics are part of the same system
3-convective flow in the mantle is the primary mechanism for transporting heat away from Earth’s interior to the surface where it is eventually radiated into space

83
Q

driving forces sof plate motion

A
  • subduction of cold, dense slabs of oceanic lithosphere (aka slab pull)
  • ridge push that results from elevated position of oceanic ridge and causes lithosphere to slide donwn the flanks of the ridge
  • mantle drag-when flow in athenosphere is moving at a velocity that exceeds that of the plate
84
Q

any acceptable model for plate-mantle convection

A

must explain compositional variations know to exist in the mantle

85
Q

types of plate-mantle convection

A

-layering and whole-mantle convection

86
Q

layering

A

2 zones, thin dynamic layer in upper mantle and thick sluggish layer underneath

87
Q

whole-mantle convection

A

cold oceanic lithosphere sinks to great depths and stirs the entire mantle
-predicted that this type would cause entire mantle to completely mix which would eliminate chemically distinct magma sources

88
Q

The unequal distribution of heat in Earth’s interior generates

A

some type of thermal convection that ultimately drives plate-mantle motion

Earth Science Unit 2 (4 decks)

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