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Ce 11 > Lecture 7: Plate Tectonics > Flashcards

Lecture 7: Plate Tectonics Flashcards

1
Q

Father of Plate Tectonics

A

Alfred Wegener

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2
Q

Pangaea

A

Supercontinent

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3
Q

1915

A

The Origin of Continents and Oceans

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4
Q

Political Problem of Plate Tectonics

A

Alfred Wegener is German while most of the geosciences was based in US and Britain

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5
Q

Proofs of Continental Drift Theory

A 
• Matching fossils in continents
separated by large waters
• Matching geological patterns
• Karoo Glaciation found in South America, Africa, Australia, and Antarctica which can only happen (according to Wegener) if they
were connected.
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6
Q

What moved the continents according to Alfred Wegener?

A

1The continents are icebergs on heavier SiMa crust
2Forces available to push the continents are
• Earth rotation effect
• Lunar and solar tidal forces

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7
Q

The proposal of Hess on sea floor spreading was called?

A

GEOPOETRY

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8
Q

Geopoetry was released on what year

A

1962

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9
Q

What are the ideas under Geopoetry?

A

•Ocean Ridges form new seafloor (from mantle material) while the old
seafloor is pushed and subducts to be reintroduced to mantle
• Movement is driven by mantle convection cells (remember the convection
currents where material goes up in ridges and goes down at trenches?)
• Continental crust does not descend but are lifted up as mountains – only
oceanic crust descends.

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10
Q

What year was magnetometer readings done to study ocean floor topography

A

1961

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11
Q

He noticed that the magnetic pattern is symmetric with respect to ocean ridges. The pattern showed alternating stripes of normal and reverse
magnetic polarity of rocks.

A

Vine

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12
Q

1963

A

Vine and Matthews (Vine’s Ph.D. supervisor) proposed

that the patterns are related to magnetic reversals.

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13
Q

The material from the mantle that rises up through the midocean ridge is______ that contains magnetite – a rock mineral that is highly magnetic and aligns with the magnetic field.

A

basalt

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14
Q

How are the stripes and magnetic reversal related?

A

• The material from the mantle that rises up through the midocean ridge is basalt that contains magnetite – a rock mineral that is highly magnetic and aligns with the magnetic field.
• As the material hardens, the magnetic field recorded gets “locked in” in the rock.
• Material is created again at the ridge, pushing out the
material before it
• When the earth’s magnetic field reverses, it is also recorded in the material. Hence the symmetry of magnetic record with respect to mid-ocean ridges)

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15
Q

Who is Morley?

A

Morley is also another geologist who came up

with the same idea independently from Vine and Matthews.

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16
Q

Who is John Tulzo Wilson?

A

Proponent of Mantle plume or Hot Spot

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17
Q

Hot Spot

A

• Spot where hot mantle material goes up through the
crust and up above the surface.
• It is non-moving and semipermanent

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18
Q

Hot Spots are found aroun the world mostly in ocean basins, name a hot spot found in a continent

A

Yellowstone hotspot

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19
Q

Oceanic ridges appear curved but are actually straight. The curve in the ridges are caused by offsets caused in turn by faults perpendicular to the ridge. What are these faults called?

A

Transform Fault

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20
Q

1965

A

Tuzo coined the term Transform Fault

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21
Q

At transform faults, plates

A

Move in opposite direction

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22
Q

Introduced the ideas of “plates” making up the crust.

A

John Tulzo-Wilson

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23
Q

1967

A

Plate maps are made

24
Q

Name the Major plates (Top to bottom and Left to Right)

A

Eurasia, North America, Australia, Pacific, South America, Africa, India, and Antarctic

25
Q

Plate Tectonic’s Rate of motion

A

1 – 10 cm/yr

26
Q

The movement of Plate Tectonics

A

Translational and Rotational

27
Q

Name the types of Plate Boundaries

A

Divergent, Convergent, Transfrom

28
Q

Spreading boundaries

A

Dirvergent

29
Q

Crustal material created by Diverging plates

A

mafic igneous rock – Basalt or Gabbro

30
Q

How are Pillow Lavas form?

A

Pillow lavas are formed when the lava flows out into the water

31
Q

How are Sheeted Dykes form?

A

Formed when the ridge opens up and a

column of magma cools in the crack.

32
Q

3 types of convergent boundaries

A
  • Ocean – Ocean
  • Ocean – Continental
  • Continental - Continental
33
Q

Ocean Trenches form from what type of convergent boundary

A

Ocean-ocean

34
Q

Which plate submerges during ocean-ocean convergence?

A

The Denser plate (older and colder)

35
Q

How are chain of volcanic islands form?

A

During o-o convergence, Magma forms underneath (via flux melting*) and rises up

36
Q

Which plate submerges during ocean-continent convergence?

A

Oceanic Platee

37
Q

This is formed during o-c convergence when accumulated sediment on continental slope is thrust up

A

Accretionary Wedge

38
Q

Happens when the plate has moved so much

A

Continental-continental Convergence

39
Q

Why are 2 continental plates both lifted up during convergence?

A

Because no plate is denser

40
Q

Plates slides across each other without
creation or destruction of crustal
material.

A

Transform Boundary

41
Q

Upwelling of mantle causes newer and warmer

material to form that will in turn be pushing older and colder material away from the ridge.

A

Ridgepush

42
Q

Older and colder plate segments at subduction zones

become colder and denser thus goes down further and pulls the rest of the plate attached to it

A

Slab pull

43
Q

Which moves faster? Plates with or without subducting part?

A

With

44
Q

Does bigger area means bigger traction velocity

A

No. Plate area is not related to its velocity

45
Q

Main mechanisms of plate movement

A

1 Convection
2 Ridge push
3 Slab pull

46
Q

3 magma forming plate-tectonic setting

A
  • Divergent boundary (via decompression melthing)
  • Convergent boundary (via flux melting)
  • Mantle plume (via decompression melting)
47
Q

Melting or partial melting of hot rock as
pressure on it is reduced (while temperature remains roughly the
same)

A

Decompression Melting

48
Q

When water is added into a rock, it lowers the melting

point of the rock.

A

Flux Melting

49
Q

Composite volcanoes form at ________ boundaries

A

Convergent

50
Q

shield volcanoes are formed from

A

Mantle plumes, continental rifting

51
Q

the elongation/stretching of the crust in
some areas resulting to its thinning. Since it is thin, it allows rising of mantle material. It forms shield volcanoes and cinder cones

A

Continental Rifting

52
Q

This can be observed in mantle plumes, divergent

boundaries and ocean-ocean convergent boundaries.

A

Seafloor volcanism

53
Q

What percent of utramafic mantle becomes mafic magma in the zone of partial melting>

A

~10%

54
Q

rocks are buried deep (10-20km

typically), usually related to convergent boundaries, and spans thousands of km^2

A

Regional Metamorphism

55
Q

a body of magma in the upper part
of crust can be the source of heat and metamorphose rock around it. The zone of contact metamorphism is a few meters up to tens of meters.

A

Contact Metamorphism

56
Q

Resulting rock of Oceanic crust metamorphism on either side of the ridge

A

Greenstone and Greenschist

Ce 11 (11 decks)

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