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Geography- Hazards > Plate Tectonics > Flashcards

Plate Tectonics Flashcards

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1
Q

Crust

A

Earth’s outer shell, between 6-70km thick

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2
Q

Mantle

A

Molten/ semi-molten layer rock layer

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3
Q

Outer Core

A

Molten outer layer of the core, mainly iron

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4
Q

Inner Core

A

Solid centre, made of iron and nickel alloys- up to 5000°c

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5
Q

Asthenosphere

A

Layer beneath the lithosphere that’s semi-molten and the plates float on

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6
Q

Lithosphere

A

Crust and the rigid upper section of the mantle, divided into the tectonic plates

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7
Q

Oceanic Crust- Thickness

A

6-10km

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8
Q

Oceanic Crust- Age

A

> 200million

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9
Q

Which is denser- oceanic or continental crust?

A

Oceanic

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10
Q

Oceanic Crust- Example of rock

A

Basalt

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11
Q

Continental Crust- Thickness

A

30-70km

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12
Q

Continental Crust- Age

A

<1500million

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13
Q

Continental Crust- Example of rock

A

Granite

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14
Q

What are the 2 internal energy sources?

A

Primordial Heat

Radiogenic Heat

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15
Q

What’s primordial heat?

A

Heat left over from Earth’s formation

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16
Q

What’s radiogenic heat?

A

Heat produced by the decay of isotopes like Uranium 238

By far the greatest source, but slowly diminishing

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17
Q

Explain Alfred Wagner’s theory (1912)

A

Continental Drift- 300 million years ago Pangea existed

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18
Q

List 5 pieces of evidences supporting continental drift

A 
Fossil Fit
Tectonic Fit
Geological Fit
Jigsaw Fit
Paleomagnetism
19
Q

Fossil Fit Example

A

Mesosaurus found in South Africa and East America

20
Q

What type of fossils are looked at? Why?

A

Land mammals

Don’t swim, don’t lay eggs

21
Q

Tectonic Fit Example

A

Caledonian mountain belt found in Scotland, Canada and Greenland- form a continuous linear pattern when reassembled

22
Q

Why does tectonic fit support Continental Drift?

A

As mountain belts have to be made under the same conditions in the same location

23
Q

Geological Fit Example

A

Mapping South America and West Africa reveals continuous rock outcrops over 2,000 million years old

24
Q

Jigsaw Fit Example

A

Coastlines of South America and West Africa match to a depth of 1,000m below current sea level

25
Q

How can gaps and overlaps in jigsaw fit be explained?

A

Coastal erosion
Coastal deposition
Rises in sea level
Changes in land level

26
Q

How does paleomagnetism explain Continental Drift?

A

Roughly every 400 million years the Earth’s magnetism changes
At mid ocean ridges, there are striped symmetrical patterns where the rock has moved apart due to sea floor spreading
Shows that the plates are moving

27
Q

Sea Floor Spreading

A

Movement of oceanic crust away from constructive plate margins at mid-ocean ridges

28
Q

Slab Pull

A

After subduction, the cooler, heavier edge of the lithosphere sinks into the mantle under its own weight, pulling the plate with in

29
Q

Ridge Push

A

The higher elevation at mid ocean ridges causes gravity to push the lithosphere that’s further from the ridge

30
Q

Gravitational Sliding

A

Movement of tectonic plates as a result of gravity

31
Q

Benioff Zone

A

Where plates melt in the mantle due to increasing heat and friction

32
Q

Constructive Margin

A

Plates move apart

Magma rises from the asthenosphere and cools, filling the gap

33
Q

Constructive Margin Features (and examples)

A

Shield volcanoes- Eyjafjallajokull
Earthquakes
Rift valleys- East African Rift Valley
Mid-Ocean Ridges- Mid-Atlantic Ridge

34
Q

Oceanic- Oceanic Margin

A

2 Oceanic plates move towards eachother
Faster/ denser subducts
Melts in Benioff Zone
Less dense molten material rises

35
Q

Oceanic- Oceanic Margin Features (and examples)

A 
Ocean trenches- Mariana Trench
Island Arcs- West Indes
Earthquakes
Composite volcanoes- Montserrat
Tsunamis- Boxing Day
36
Q

Oceanic- Continental Margin

A

Oceanic and continental move towards eachother
Denser oceanic subducts
Melts in Benioff Zone
Less dense molten material rises

37
Q

Oceanic- Continental Margin Features (and examples)

A

Ocean Trenches- Peru-Chile Trench
Composite volcanoes- Cotopaxi
Fold mountains- Himalayas

38
Q

Continental- Continental Margins

A

Continental plates move towards eachother
Both plates have a lower density than asthenosphere
Can’t subduct
Collide and rise upwards

39
Q

Continental- Continental Margin Features (and examples)

A

Earthquakes

Fold Mountains- Himalayas

40
Q

Conservative Margin

A

Plates move past eachother
Friction between plates= stress builds
Suddenly released

41
Q

Conservative Margin Features (and examples)

A

Fault line- San Andreas

Shallow earthquakes

42
Q

Hotspots

A

Small area with unusually high concentration of radioactive elements below the surface
(Magma Plumes)

43
Q

Hotspot Feature (and example)

A

Shield volcanoes- Mauna Loa, Hawaii

44
Q

Magma Plume

A

Rising column of hot rock at a plate margin or through a plate

Geography- Hazards (13 decks)

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