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EAS 205 > continental drift + plate tectonics > Flashcards

continental drift + plate tectonics Flashcards

1
Q

what is a continental drift?

A

continents moved and rotated over geological time

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2
Q

why did alfred wagner think continents work?

A
  1. a jigsaw puzzle
  2. glaciation in places now located in the tropics, warm things like coal are up in the artics now
  3. desert sands in area that now have moist, temperate climates
  4. remains of the tropical plants in the antarctic
  5. fossil remains of plants and animals that lived in restricted areas but now are widely separated geographically
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3
Q

since the rocks (continents) are very similar, this shows proof they?

A

were likely joined together

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4
Q

the continents were once _____, and then what happened to them?

A

was one giant ice sheet that eventually broke up and spread them apart

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5
Q

In 1950 - 1960, the idea revived about continents moving by scientists studying?

A

strength of rocks, earth’s magnetism and ocean floor

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6
Q

if the continents solid and mantle solid, how can it move?

A

time, temperature and scale / pressure!!!

ex: ice: they have intricate ice sculptures in ice, but the ice can melt into glacier streams

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6
Q

how does the magnetic field circle the earth (direction)?

A

out and around

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7
Q

what did blackwell think the source of magnetism is?

A
  • thought it had something to do with spinning
  • outside sphere spins faster than inside
  • theory was wrong
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8
Q

what is paleomagnetism?

A

rocks pointing the same direction ended up being different in magnetism patterns in one place than in another

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9
Q

what is the curie point?

A

atoms stop bouncing when cooled, and atoms will record direction of magnetic field when it passes through that temperature

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10
Q

earths magnetic field will arrange the particles direction in terms of?

A

the sediments direction

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11
Q

the lines of force at pole go in what direction?

A

straight up and down

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12
Q

polar wander curves show?

A

the paths of a magnetic pole with respect to a given continent

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13
Q

what showed proof that the continents had moved?

A

same age rock: measure which way north pole is pointing
- different continents were not pointing toward the same pole
- should be pointing toward the same pole
- proof continents had moved

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14
Q

what is magnetic reversal?

A

magnetic north has changed throughout time
earths magnetic field periodically switches signs

ex. 1927: matuyama was hiking across a volcano carrying a compass, and found that the compass pointer flipped on each layer of rock

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15
Q

what are excursions?

A

when the magnetic field almost switches signs, but didn’t

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16
Q

how long does it take for switches to take place?

A

3000 - 4000 yrs

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17
Q

the megntic field was probably zero at sometime, what would this have done to the earth?

A

we would be bombarded from harsh radiation

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18
Q

what are geomagnetic reversals?

A

magnetic field collapsed for awhile, but did not quite switch

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19
Q

what happens if there is no magnetic shield?

A

carbon 14 will be more abundant
O2 molecules will create ozone

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20
Q

how do we create a new seafloor?

A

magnetic reversals: magma chills, freezes in magnetism of that day

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20
Q

the creating of a new sea floor in terms of magnetic reversals is what kind of pattern?

A

predictable: it is symmetric on both sides

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20
Q

seafloor spreading explains the?

A

magnetic patterns on the sea floor

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20
Q

seafloor spreading explained by magnetic patterns on the sea floor was first published in what journal?

A

nature

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21
Q

what can seafloor spreading rates vary between (in cm/yr)?

A

0.5 - 20

22
Q

how many square kilometers of sea floor are created each year?

A

3

23
Q

how was sea floor spreading confirmed?

A
  1. dating through study of fossils
  2. dating of rocks sampled by seafloor drilling
  3. crust is youngest at ridges
  4. sediment thicken away from ridge
24
Q

the ship that drilled the mantle on the seafloor is called the?

A

glomar challenger

25
Q

in 1968, our new paradigm formed to explain why continents are moving and midocean ridges are spreading. what is it called

A

plate tectonics

26
Q

what is the theory of plate tectonics?

A

distribution of volcanoes and earthquakes are not random, and earthquakes follow mid-ocean ridges.

27
Q

how are plate tectonics created?

A
  1. deep inside the earth is hot, as you approach the surface it is cool.
  2. upper mantle is chilled, therefore brittle. lower mantle is hot, so it is soft.
  3. this division creates plates, as the soft, gooey stuff underneath pushes the solid, brittle plate
28
Q

the outside layer that sits on the soft asthenosphere is called the?

A

lithosphere

29
Q

what is the plastic layer beneath the lithosphere?

A

asthenosphere

30
Q

how do plate tectonics express itself? how does this process occur?

A

through rising
as it cools, thickness of plate grows, gets denser, heavier, and sinks

31
Q

what is the convergent plate boundary?

A

plates move toward one another on a collision course

32
Q

what is a divergent plate boundary?

A

plates separate one another

33
Q

what is the transform plate boundary?

A

plates must rub against another / slide past another

34
Q

what is a de fuca plate?

A

tiny plate broken off

35
Q

why do plates move?

A

convention
rising ht magma under mid-ocean ridges builds up in new lithosphere, which cools as it spreads away, and eventually sinks back into the mantle where it is melted

36
Q

what crest is the sea floor created at?

A

mid-ocean

37
Q

in divergent boundaries with sea floor spreading, how are the different layers created?

A
  1. seawater circulates through hot basalts
  2. basalt heated and reacts with rock
  3. rock becomes metal rich
  4. resurfaces black smokers
  5. meets cold sea water
  6. precipitates valuable mineral deposits
38
Q

what controls the composition of sea water?

A

chemical exchange between water and basalts

39
Q

how is a black smoker created?

A

sulfur is mixed with oxygenated water

40
Q

how can a black smoker evolve bacteria communities?

A

bacteria can utilize sulfur, those bacteria grow, and filter feeders filter out the sulfur, and community evolves

microbes live off of carbon dioxide and sulfur that comes out, generating a beginning of food chain

41
Q

what is a food chain without sunlight called?

A

lithotrophic

42
Q

what are the two ways plates can break up and move?

A
  1. plates can separate from each other
  2. rifting: spreading of ocean breaking up a continent
43
Q

we create 3km/yr in sea floor spreading, but somehow it must be ridden of, how do we get rid of it?

A

convergent boundaries (making things collide and break up)

44
Q

what is the deepest place in the ocean?

A

ocean trenches

45
Q

how are ocean trenches created?

A
  1. sea floor is spreading
  2. creates new plate
  3. plate is shrinking then contracted
  4. gets dense and it starts sinking 5. plate will bend, bend creates trench
46
Q

what is an ocean continent convergence that is close to us?

A

the cascades

47
Q

what happened to the trenches during the ice age?

A

so much sediment dumped off the continent that the trenches became filled

48
Q

what are transformed faults?

A

numerous short segments where two opposite plates scrape past each other

49
Q

why must plates break up?

A

to move around the earth (a sphere)

50
Q

older rock?

A

shrinks and sinks

51
Q

younger rocks?

A

high and warm

52
Q

what is the lost city?

A

life developed in the ridges between old and young crust

53
Q

what is a volcanic trail?

A

heat source under the water that is burning through the plate

54
Q

what is a mantle plume?

A

jets of hot material rising from deep in the mantle

55
Q

what is dynamic topography?

A

how the mantle and crust is pushing up continents

56
Q

what do mantle plumes lead to?

A

large igneous provinces

57
Q

what is believed to happen in 250 million years?

A

reform supercontinent

58
Q

if we create a supercontinent in the future, what would happen?

A

landmass would be so hot that mammals could not exist

EAS 205 (17 decks)

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