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AQA Geography A level Physical > Plate Tectonics > Flashcards

Plate Tectonics Flashcards

1
Q

What is a conservative plate margin?

A

Plates which are sliding past each other horizontally

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2
Q

Describe how a conservative plate margin functions (5 things)

A
  • describe what a conservative plate margin is
  • crust is neither produced or destroyed
  • plates are made of rock that has jagged edges so they catch and snag against one another
  • friction and pressure between the plates builds until the plates can’t take the stress
  • the plates slip past each other, which can cause both plates to move resulting in the ground shaking
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3
Q

What is a destructive plate margin?

A

When an oceanic plate slides beneath the continental plate

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4
Q

Describe how the destructive plate margin functions (5 things)

A
  • describe what a destructive plate is
  • crust is destroyed as one plate dives under another at the subduction zone
  • the rocks catch against each other as the plates are not smooth
  • the pressure between the plates builds until the plates can’t take the stress
  • the plates slip past each other which can cause both plates to move resulting in the ground shaking
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5
Q

What is a constructive plate margin?

A

When the plates move apart (diverge)

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6
Q

Describe how a constructive plate margin functions? (5 things)

A
  • describe what a constructive plate is
  • convection currents diverge and cause a gap between the plates
  • magma rises up to fill the gap that is caused
  • new crust is generated as the plates pull away from each other
  • rift valleys are created when the crust pulls apart, and land drops to create a valley
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7
Q

What are the two types of tectonic plates?

A
  • oceanic
  • continental
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8
Q

Give me 4 facts about oceanic plates

A
  • high-density material
  • made of basaltic rock
  • only 7-10km thick
  • can sink (subduct) under other plates
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9
Q

Give me 4 facts about continental plates

A
  • thicker (25-75km)
  • less dense
  • made of granite rock
  • do not subduct
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10
Q

Give me the 4 landforms at destructive plate boundaries

A
  • deep sea trenches
  • volcanoes
  • young fold mountains
  • island arcs
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11
Q

Give me an example of a deep sea trench and explain what happens

A

Examples: Mariana Trench
Where the pacific plate is subducted under the Philippine plate

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12
Q

Explain how volcanoes in destructive plays margins occur and one fact about where it doesn’t happen?

A
  • melted plate rises to the surface
  • there are no volcanoes at destructive collision boundaries or conservative boundaries as there is no subduction
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13
Q

Give an example of a young fold mountain and explain how it forms?

A
  • between 10 & 25 million years old
  • created at both destructive subduction and destructive collision boundaries
  • plates move together, sediments in the sea core pushes up into fields between them
  • examples:
    Himalayas - collision boundaries
    Andes - subduction boundaries
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14
Q

Give me an example of an island arc and how it forms?

A
  • examples : Marianas island arc (runs parallel to the Marianas Trench
  • forms at destructive subduction boundaries, when the descending plate melts and material rises towards the surface as plutons of magma
  • when they reach the surface they form volcanoes which may erupt offshore, causing a line of volcanic islands
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15
Q

Give me 3 landforms at constructive boundaries

A
  • rift valleys
  • volcanoes
  • ocean ridges
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16
Q

Give an example of how a rift valley functions

A
  • example: east Africa
  • two continental plates are pulling apart
  • as the crust thins, it is heated and bulges, forming cracks
  • when an area of crust drops down between parallel faults this is known as a rift valley
17
Q

Give an example of an ocean ridge and how they form?

A
  • example: mid-Atlantic ridge
  • two oceanic plates are moving apart
  • as pressure is reduced, the semi-molten magma of the mantle melts and rises up into the gap between the plates, forming a ridge
18
Q

Explain how hotspots occur? (3 things)

A
  • there is a hot mass of rising heat under a weakness in a plate
  • magma rises to the surface through this weakness
  • the Hawaiian islands all formed as a result of a mid-pacific hotspot
19
Q

What is a hotspot?

A

an area of the Earth’s mantle from which hot plumes rise upward

20
Q

Explain how Intra-plate volcanoes form (3 things)

A

-isolated plumes of convecting heat (mantle plumes) rise towards the surface generating basaltic volcanoes
- the plume remains stationary, although the tectonic plate above moves slowly over it
- continuing plate movement over time produces a chain of volcanic islands, with extinct ones furthest from the plume location

21
Q

Explain how intra-plate earthquakes form (2 things)

A
  • can happen in mid-plays settings, usually associated with ancient fault lines being re-activated by tectonic stresses (e.g. minor earthquakes in the UK)
  • zones of weakness are created as plates move and stress increases
22
Q

Describe the earth’s internal structure (inside-outside)

A
  • the core
  • the mantle
  • the asthenosphere
  • the lithosphere
23
Q

Describe the core: (4 things)

A
  • Central Part of the earth
  • solid at the centre
  • more liquid further away
  • source of radioactive heat
24
Q

Describe the mantle: (2 things)

A
  • semi-molten body of rock
  • between the Earth’s crust and its core
25
Q

Describe the asthenosphere:

A
  • upper part of the mantle
26
Q

Describe the lithosphere: (3 things)

A
  • the crust and upper mantle
  • 80-90km thick
    -this form the tectonic plates
27
Q

Name the 5 theories of plate tectonics

A
  • holmes’ hypothesis
  • slab pull
  • gravitational sliding
  • wegener’s continental drift
  • sea floor spreading
28
Q

What does holmes’ hypothesis talk about?

A

Holmes (1930s) said that the Earth’s internal radioactive heat was the driving force of convection currents in the mantle that could have moved tectonic plates

29
Q

What does slab pull talk about?

A

At convergent boundaries, high density ocean floor is being dragged down by a downward gravitational force beneath the adjoining continental crust

30
Q

What does gravitational sliding infer?

A

Elevated altitudes of oceanic crust at ridges at divergent plate boundaries. Create a ‘slope’ down which oceanic plates slide

31
Q

Wegener’s continental drift

A

1912: he said our now separate continents had once been joined together as a super-continent (Pangea)

32
Q

What does sea floor spreading infer about (2 things)

A
  • 1960s: there was a discovery of magnetic strips in the oceanic crust of the seabed
  • palaeomagnetic signals from past reversals of the earths magnetic field prove that new crust is created by the process of seafloor spreading at mid-ocean ridges

AQA Geography A level Physical (3 decks)

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