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earth history > unit 4 1-50 test 51-55 quiz 6 56-60 quiz 7 > Flashcards

unit 4 1-50 test 51-55 quiz 6 56-60 quiz 7 Flashcards

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1
Q

what is the diameter of the earth?

A

8,000 miles

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2
Q

what is the diameter of the sun?

A

800,000 miles

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3
Q

what is earths circumference?

A

24,000 miles

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4
Q

describe earths three distinct, concentric layers

A

iron core is larger than 1/2 of earths diameter
mantle composed of ultramafic rocks and minerals
two types of earth crust
oceanic mafic crust (basalt)
continental felsic crust (granitic)

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5
Q

what two types of crust does the earth have?

A

oceanic mafic crust (basalt)

continental felsic crust (granitic)

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6
Q

describe the three sources of earths residual heat?

A

heat from gravitational energy
heat derived from kinetic energy generated by planetesimal collisions
heat generated from later meteor impacts (4.6-3.8 billion years)

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7
Q

heat from within the earth is continually generated by

A

radioactive decay
with melting metallic iron and nickel sank to the center of the earth to form the iron core (iron catastrophe)
the remaining melt was composed of mafic or basaltic rocks that surround the ultramafic earths mantle

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8
Q

what is a lithosphere and where is it located?

A

rigid outer layer containing crust and a frozen part of the upper mantle

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9
Q

what is the asthenosphere and where is it located?

A

partially melted upper mantle that has plastic-like properties

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10
Q

describe the lower mantle and where is it located?

A

(sometimes called the mesosphere) solid layer of rocks between the asthenosphere and iron core

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11
Q

describe the components of earths core and where are they located

A

liquid iron core molten iron with some nickel and rocks (half diameter of earth)
solid iron core +6,000 degrees celceus

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12
Q

what happened to most of the hydrogen and helium that accumulated with earths mass?

A

most of it escaped from earth because earth did not have enough gravity to hold these elements within its atmosphere

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13
Q

how much free oxygen was available very early in earths history?

A

there was almost no free oxygen with earths original atmosphere

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14
Q

what does the presence of pyrite grains in early sedimentary rocks imply?

A

proof that there was no free oxygen cause they didn

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15
Q

describe the occurrence of banded iron formations during early times(2.5-2.0 billion years)

A

having more generated free oxygen the banded iron formations (that require abundant oxygen) became thick and cover vast areas. by this time, free oxygen consumed all the dissolved iron in the oceans

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16
Q

which ancient life forms were present at least 3.5 billion years ago that began creating earths free oxygen?

A

ancient bacteria and algae these life forms used photosynthesis to combine co2 and water into organic molecules and release free oxygen as a waste product into the atmosphere

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17
Q

what is the approximate percentage composition of earths atmosphere today?

A

approximately 78% nitrogen and 21% oxygen (rounded 80%-20%)

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18
Q

what happened to most of the co2 that was present in early earths atmosphere?

A

a small fraction of co2 was converted into oxygen
seawater absorbs co2 from the atmosphere
because of limestone we have very little co2 in our atmosphere

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19
Q

how long did it take earths oceans to reach its current salinity levels?

A

as early as the oceans formed 3.5 to 4.4 billion years

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20
Q

alfred wegener was famous for proposing which scientific theory?

A

continental drift theory in 1915

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21
Q

what was pangaea.

A

the last known super-continent in which all the present-day continents did not stay in the same area over geologic time.

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22
Q

remember that wegener used fossils, striations and age of rocks to prove continental drift?

A

a super continent model because
similarities in shoreline of continents
dist\tinctive rock formations on matching continents
distinctive matching fossil groups

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23
Q

why was the theory of continental drift rejected?

A

he could not provide a mechanism to move the continents

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24
Q

what is the current theory about the creation of earths magnetic field?

A

creates a huge magnetic shield that prevents the earth from being blasted by cosmic particles from the sun

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25
Q

what evidence do we have for earths magnetic shield?

A

the aurora borealis is evidence of earths magnetic shield

26
Q

describes what happens to a magnetite grain when it cools within a basaltic magma.

A

the grains align themselves to earths magnetic field that is present at that time

27
Q

define paleomagnetism and why is it an important geologic tool.

A

the study of magnetic fields, as preserved in the magnetic properties of rocks
magnetic fields that are preserved in ancient lava flows can be used to demonstrate that earths continents have moved over time

28
Q

who proposed the theory of seafloor spreading?

A

dr. h. h. hess (1906-1969) in 1960 his theory of sea floor spreading as a method to move and separate the continents

29
Q

magnetic polarity stripes (magnetic reversals) are__ on both sides of the mid-oceanic ridge.

A

identical polarity stripe on both sides of the ridge thus they are symmetrical on each side of the oceanic ridge

30
Q

what is the name of the deepest submarine trench?

A

mariana trench more than 36,000 feet depth (about 7 miles)

31
Q

compare the age of basalt at the oceanic ridge to its age at the edge far from the ridge

A

it becomes older on both sides of the ridge as one moves away from the ridge toward the continents

32
Q

what is a tectonic plate?

A

a single block of lithosphere that moves about the earths surface
plates are outlined by ridges, trenches and mountains
individual tectonic plates are based on structural features, not on continents and oceans

33
Q

describe a divergent plate boundary, including the movement of neighboring plates.

A

mid oceanic ridge also called a spreading center or central rift zone
divergent zones are located within the ocean floor where of sea-floor spreading basalt is creating new oceanic crust
plates are being moved apart or away from each other (tension) where vertical injections of basalt fill the fracture zones.

34
Q

describe a transform plate boundary, including the movement of neighboring plates?

A

sliding plate boundary
plates slide past one another
these are directly associated with divergent zones.
the san andreas fault is a transform fault

35
Q

describe a convergent plate bouddary, including the movement of neighboring plates?

A

subduction zones
this area is where the plates comes together(compression) these zones are where continental crust is created most metamorphic rocks are created here.
plate motions are complex involving geometry of a curved plate moving on a sphere

36
Q

which tectonic zone can create an ocean basin?

A

divergent plate boundary

divergent zones

37
Q

where tectonically are all black smokers located?

A

divergent zones mid oceanic ridge that rises high above the ocean floor
hot water escapes in fountains along these zones

38
Q

what do we call a divergent zone on land?

A

rift (zone) valley

39
Q

what are the three types of convergent zones?

A

two oceanic crusts meet making volcanic mountains called island arc
oceanic crust is subducted creates mountains
two continental crusts collide creating gigantic mountains

40
Q

define a subduction zone.

A

a locality where oceanic crust is being pushed or subducted into the mantle (directly associated with deep-sea trenches or convergent zones)

41
Q

where tectonically are the deep sea trenches located?

A

subduction zone

42
Q

what is the most favored theory or mechanism today for plate tectonic movements?

A

slab pull theory weight of the slab entering the mantle will pull the crust remaining into the mantle

43
Q

give an example of a landmass created by a mantle plume or hotspot?

A

magma that rises from deep inside the mantle, with a continuous supply of magma that may last for 100 million years, even as the overlying plate moves
hawaii is the result of a mantle plume or hotspot

44
Q

describe a super-continent cycle and who came up with the name?

A

about every 500 million years, most of earths continents collide together, then later split apart
j. tuzo wilson

45
Q

how is science different from other fields of human endeavor?

A

science searches for regularities and patterns in the natural world.

46
Q

why is it that many aspects of being human are not amenable to scientific description?

A

because of culture and opinion

47
Q

which subjective sciences are not normally addressed by normal science?

A

justice and honor that varies by culture-not science

esthetics and manners, etc. - these vary by culture and not by science

48
Q

questions that science can address are limited by___?

A

the properties of the natural world
the instruments available to extend human sense
socially imposed missions
the paradigm that guide scientific inquiry

49
Q

how absolute is scientific knowledge?

A

is not absolute
is tentative, approximate and subject to revision
also applies to the earth sciences

50
Q

with many publicized articles about global warming, should they also give reasons that do not fit the model?

A

yes they should

51
Q

what name did edward suess propose for a super-continent in 1885?

A

gondwanaland or gondwana

52
Q

the picture on page 31 figure 2.5 shows lines of glacial movement. what are these lines

A

striations

glacial striations scratch marks

53
Q

the temperature at which magnetite can gain or loses it remnant magnetism from heating?

A

curie point

54
Q

as a group how many geologists accept that plates are created at oceanic ridges and destroyed at deep sea trenches?

A

most

55
Q

the lithosphere overlies the hotter and weaker semi-plastic?

A

asthenosphere

56
Q

the eoarchean era ended ____ago.

A

3.6 billion years

57
Q

this figure is illustrating the origin of ______

A

granitic continental crust

the first protocontinents formed

58
Q

the archean eon alone accounts for____of all geologic time.

A

32.6%

59
Q

the approximate age of the oldest detrital zircons in australia

A

4.4 billion years old

60
Q

how many named greenstone belts are in figure 19.9

A

5

earth history (7 decks)

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