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tect 1 Flashcards

1
Q

What is the plate tectonic theory? What does it explain?

A
  • Earth has a three-layered structure
  • Earth’s litosphere is broken up into huge pieces -> “tectonic plates”
  • Tectonic plates always moving
  • Plate movements -> landforms and phenomena
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2
Q

Earth’s structure

A

Crust, uppermost mantle, mantle, core

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3
Q

What does the “ tectonic plate” contain?

A

Crust, uppermost mantle

This is what Tectonics will be focusing on

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4
Q

Two categories of crusts and where they are found

A
  • oceanic (seafloor)
  • continental (continents)
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5
Q

Which plate, continental or oceanic is denser?

A

Oceanic

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6
Q

What does the asthenosphere contain?

A

Semi-solid Upper mantle

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7
Q

What causes the athenosphere to be semi-solid?

A

Heat from the core causes the rocks in the Upper mantle/athenosphere to melt

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8
Q

Core mantle crust temperature and thickness

A

Core: 4400-6000deg, 3300km
Mantle: 1000-3700deg, 2900km
Crust: Lowest, 6-70km

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9
Q

What are the types of plate boundaries? What causes the plate boundaries to exist?

A

Types of plate boundaries
Divergent
Convergent
Transform

What causes them to exist?
Convection Currents
Slab-pull force

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10
Q

Describe what happens at divergent, convergent and transform boundaries

A

Divergent -> Plates move away from one another
Convergent -> Plates move towards one another
Transform -> Plates slide past one another

MEMO
Diverge means move away, so the “plates” will move away from each other.

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11
Q

How does convection currents lead to Divergent plate movement?

A
  1. Heat from Earth’s core -> mantle material to decrease in density
  2. Mantle material rises to surface
  3. Rising convection currents spreads magma beneath plates, dragging them apart.
  4. Mantle then loses heat and sinks back towards the core
  5. The material gets heated up again, repeating the process.

For 4:
Mantle material cools because it is at the area beneath plates that is further from the core which is the heat source, so its cooler there and the mantle material cools down, becomes denser and sinks.

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12
Q

When two convection currents collide with each other, plate movement is…?

A

Convergent

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13
Q

How does slab-pull force contribute to convergent plate movement?

A
  1. When two plates converge, denser crust is pulled down by gravity
  2. It subducts under the less dense crust, sinking under it’s own weight, pulling down the rest of the plate with it
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14
Q

What is subduction? Does it happen to oceanic crust, continental crust or both?

A

Happens to…?
Oceanic crust only. Only denser oceanic crust can subduct

What is subduction? No need memo, just know the rough meaning
Oceanic plate colliding with another tectonic plate (can be continental e.g.) and the oceanic plate descending under the other tectonic plate

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15
Q

Magma VS Lava

A

same thing except for location
Magma -> In the volcano
Lava -> Outside of volcano

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16
Q

How does seafloor spreading occur?

A
  • At O-O divergent plate boundaries, when the plates diverge, a mid-ocean ridge is formed
  • Magma rises from the weakened part of the crust and fills it
  • New seafloor is formed after the magma is cooled.

Weakened part of the crust is as a result of the divergence (the mid-ocean ridge), you can imagine that as the plates move away, there are weaker areas of the crust just like how if you stretch an elastic material, it is more prone to breaking.

Works the same way, except that in this case, weakened parts are prone to magma rising upwards

17
Q

How is a Fold Mountain formed?

A
  1. Two plate converges, buckles and folds, forming fold mountains
18
Q

Evidence of Seafloor Spreading

A
  • Age of rocks at seabed shows a pattern

pattern
- Rocks nearest to center of mid-ocean ridge youngest
- Rocks further away are progressively older
- Shows how new oceanic crust is created at divergent boundaries

19
Q

What is Magnetic Striping?

A
  • Zebra-like pattern, normal polarity rocks alternating alongside strips of reversed polarity rocks
  • symmetrical on both sides
20
Q

What is normal polarity of Earth?

A
  • Earth has geographic North, geographic South
  • This does not change.
  • Earth has magnetic North, magnetic South
  • Magnetic North, South reversed multiple times
  • When the Magnetic North Points towards the Geographic North, and the Magnetic South Points towards the Geographic South, that is Normal Polarity.
21
Q

Magnetic Striping occurs as…?

A
  • When iron-rich lava erupts, cools and solidifies, forms basaltic rocks
  • it’s Magnetic materials point towards Earth’s magnetic North, recording evidence of Earth’s polarity at that point of time
22
Q

Three plate movements

A
  • Convergent
  • Divergent
  • Transform
23
Q

1 Divergent Boundary example

A

North American, Eurasian Plate

24
Q

1 Convergent Boundary Example

A

Nazca, South American Plate

25
Q

What forms at o-o divergent plate boundaries?

A
  • Mid oceanic ridges
  • Volcanoes
  • Rift valley
  • Earthquake
26
Q

What happens at O-O Divergent Boundaries?

A
  1. Two oceanic plates move apart
  2. Decrease in overlying pressure causes underlying mantle to melt, forms magma
  3. Magma rises thru weak areas in crust, fills gaps caused by diverging plates
  4. Lava cools, solidifies to form basaltic rocks
  5. Rocks make up new oceanic crust
  6. Mid-ocean ridge forms
27
Q

Example of Mid-Oceanic Ridge

A

Mid-Atlantic Ridge

LINK
Recall the example for o-o divergence

Eurasian and North American Plate diverge

28
Q

What is formed in divergent c-c plate boundaries?

A
  • Rift valley
  • Volcanoes
  • Earthquakes

Same As O-O diverge except for no mid-oceanic range

29
Q

Example of Rift Valley

A

East African Rift Valley

30
Q

Example of Volcano

A

Mount Kenya

31
Q

Example of Oceanic Trench

A

Mariana Trench

32
Q

What forms at convergent oceanic-oceanic boundaries?

A
  • Oceanic trench
  • Volcanoes
  • Earthquakes
33
Q

What forms at continental-continental plate boundaries

A
  • Fold mountains
  • Earthquakes
34
Q

Example of a fold mountain

A

Himalayas

35
Q

What forms at oceanic-continental convergent boundaries?

A
  • Oceanic trench
  • Volcanoes
  • Fold mountains
  • Earthquakes
36
Q

what is a chain of volcanoes called?

A

island arc

37
Q

What forms at transform plate boundaries

A
  • faults
  • earthquakes
38
Q

Example of fault

A

San Adreas Fault, USA

North American Plate slide past Pacific Plate

geo (2 decks)

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