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Q2 EARTH SCI > seafloor spreading > Flashcards

seafloor spreading Flashcards

1
Q

The mechanism that operates along the oceanic ridge system to create new seafloor.

A

seafloor spreading

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2
Q

The mechanism that operates along the oceanic ridge system to create new _____.

A

seafloor

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3
Q

Typical rates of spreading average around ______, roughly the same rate at which human fingernails grow.

A

5 cm/year (2 inches)

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4
Q

Comparatively slow spreading rates of ____ are found along the Mid-Atlantic Ridge, whereas spreading rates exceeding ______ per year have been measured along sections of the East Pacific Rise.

A

2 cm/year; 15 cm/year (6 inches)

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5
Q

The seafloor has a large _____ running through it. Deep trenches are found ___ from the ridges.

A

mountain range; far

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6
Q

The _________ of the seafloor changes.

A

magnetic polarity

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7
Q

The center of the ridge is of ______.

A

normal polarity

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8
Q

Stripes of normal and reverse polarity are found ______ on both sides of the ridge.

A

symmetrical

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9
Q

The rocks ____ to the ocean ridge were _____ than the rocks found further from the ridge.

A

closest; younger

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10
Q

This means that new rocks are formed at the ____ and push the older rocks away from the ridge based on the core sample collected from 1968, a drilling ship called the Glomar Challenger.

A

ridges

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11
Q

The seafloor has a large mountain range running through it. Deep trenches are found far from the ridges.

A

evidence of seafloor spreading

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12
Q

The magnetic polarity of the seafloor changes. The center of the ridge is of normal polarity. Stripes of normal and reverse polarity are found symmetrical on both sides of the ridge.

A

evidence of seafloor spreading

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13
Q

The rocks closest to the ocean ridge were younger than the rocks found further from the ridge. This means that new rocks are formed at the ridges and push the older rocks away from the ridge based on the core sample collected from 1968, a drilling ship called the Glomar Challenger.

A

evidence of seafloor spreading

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14
Q

The ____ seafloor is much _____than the oldest continent.

A

oldest; younger

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15
Q

The oldest ocean floor rocks ever found are ___ million years old.

A

180

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16
Q

This proves that ocean floor is being ____ therefore all ocean floor rocks are ____ compared to the age of Earth.

A

destroyed; young

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17
Q

Rocks shaped like pillows (_____) shown that molten material has erupted again and again from cracks along the mid- ocean ridge and cooled quickly.

A

rock pillows

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18
Q

The oldest seafloor is much younger than the oldest continent. The oldest ocean floor rocks ever found are 180 million years old. Remember the Earth is 4.6 billion years old. This proves that ocean floor is being destroyed therefore all ocean floor rocks are young compared to the age of Earth.

A

evidence of seafloor spreading

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19
Q

Rocks shaped like pillows (rock pillows) shown that molten material has erupted again and again from cracks along the mid- ocean ridge and cooled quickly

A

evidence of seafloor spreading

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20
Q

Stripes in the seafloor. When magma cools, the iron cools into the mineral magnetite. It lines up parallel to the Earth’s present magnetic field. This iron is like compass needles, pointing north. So, when the rock hardens, a record of the Earth’s magnetic field at that time is locked in stone.

A

evidence of seafloor spreading

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21
Q

who pioneered the seafloor spreading theory

A

Harry Hess (1906-1969)

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22
Q

Harry Hess is a Former ____ Professor at ____ University

A

Geology; Princeton

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23
Q

Harry Hess was also a Head of Princeton’s _______

A

Geology Department

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24
Q

He was also the ____ of the Space Science Board of the National Academy of Sciences.

A

Chairman

25
Q

It is a geologic process in which tectonic plates split apart from each other as a result of mantle convection.

A

seafloor spreading

26
Q

It is a geologic process in which tectonic plates ____ apart from each other as a result of __________.

A

split; mantle convection

27
Q

seafloor spreading occurs at ________

A

divergent plate boundaries

28
Q

As tectonic plates slowly move away from each other, ___ from the mantle’s convection currents makes the crust __________

A

heat; more plastic and less dense.

29
Q

The less dense material ____, often forming a ________ area of the seafloor.

A

rises; mountain or elevated

30
Q

__________ are the elevated area on the seafloor

A

Mid-ocean ridges

31
Q

how do mid-ocean ridges form?

A

-Crust cracks
-Hot magma fill the fractures and spills onto the crust
-Magma is cooled by frigid seawater.
-It forms igneous rock.
-This rock (basalt) becomes a new part of Earth’s crust.
-Subduction destroys old crust
-The two forces roughly balance each other, so the shape and diameter of the Earth remain constant.

32
Q

Divergent boundaries can develop within a continent, in which case the landmass may ____ into two or more smaller segments separated by an ____

A

split; ocean basin

33
Q

Divergent boundaries can develop within a continent, in which case the landmass may split into two or more smaller segments separated by an ocean basin

A

continental rifting

34
Q

_______ begins when plate motions produce opposing (tensional) forces that pull and stretch the lithosphere.

A

continental rifting

35
Q

Continental rifting begins when plate motions produce _______ forces that pull and stretch the lithosphere.

A

opposing (tensional)

36
Q

Continental rifting begins when plate motions produce opposing (tensional) forces that pull and stretch the _____.

A

lithosphere

37
Q

As the tectonic forces continue to pull apart the crust, the broken crustal fragments sink, generating an elongated depression called a _________, which eventually widens to form a narrow sea and then a new ocean basin.

A

continental rift

38
Q

As the tectonic forces continue to pull apart the crust, the broken crustal fragments sink, generating an elongated depression called a continental rift, which eventually widens to form a narrow sea and then a new ______

A

ocean basin

39
Q

Formation of the supercontinent Pangaea

A

200 mil yrs ago

40
Q

Presence of the Panthalassan super ocean

A

200 mil yrs ago

41
Q

Atlantic and Indian Oceans not present

A

200 yrs ago

42
Q

Initial break-up of Pangaea and formation of Laurasia and Gondwanaland

A

180 mil yrs ago

43
Q

Presence of an east-west trending basin (the Tethys sea)

A

180 mil yrs ago

44
Q

Separation of Eurasian and North

A

140 mil yrs ago

45
Q

the separation of north america and africa, which marked the opening of the north atlantic

A

150 mil yrs ago

46
Q

American Plates

A

140 mil yrs ago

47
Q

Onset of mid-Atlantic ridge development

A

140 mil yrs ago

48
Q

Early formation of the North Atlantic

A

140 mil yrs ago

49
Q

South Atlantic still closed

A

140 mil yrs ago

50
Q

Separation of the African and South American Plates

A

80 mil yrs ago

51
Q

Early formation of the South Atlantic

A

80 mil yrs ago

52
Q

Indian plate reaches equator after separation from Australia and Antarctica

A

60 mil yrs ago

53
Q

North and South Atlantic continue to widen

A

40 mil yrs ago

54
Q

Onset of Indian and Asian Plate collision, initial formation of the Himalayas

A

60 mil yrs ago

55
Q

North and South Atlantic achieve modern appearance

A

60 mil yrs ago

56
Q

Major uplift of the Himalayas and formation of the Tibetan Plateau

A

20 mil yrs ago

57
Q

Expansion of the Southern Ocean

A

20 mil yrs ago

58
Q

Closure of mid-American seaway as North and South American plates collide

A

5 mil yrs ago

59
Q

Isolation of the Pacific and Atlantic Oceans

A

5 mil yrs ago

Q2 EARTH SCI (5 decks)

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