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Geography A Level > 2 + A. Tectonic Plates > Flashcards

2 + A. Tectonic Plates Flashcards

1
Q

What are the key features of Continental crust?

A

Continental crust is:

  • located below land masses and shallow seas
  • 30-60 km thick
  • made of old rocks (granite)
  • is less dense than oceanic crust
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2
Q

What are the key features of Oceanic crust?

A

Oceanic crust is:

  • Located below deep ocean
  • 5-8km thick
  • made of young rocks (basalt)
  • denser than continental crust
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3
Q

What causes tectonic plates at plate boundaries to move?

A

Tectonic plates are moved by sub-crustal convection currents in the mantle.

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4
Q

Draw a diagram of a divergent (constructive) plate boundary:

A

The diagram should feature:

  • Mantle
  • Reference to sub-crustal convection currents
  • Reference to two tectonic plates (Eurasian vs North American for Iceland) being pulled apart
  • Volcanic island / Shield Volcano / volcanic ridge in gap between plates
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5
Q

What types of volcanoes form at divergent (constructive) plate boundaries?

A

Types of volcanoes at divergent (constructive) plate boundaries:

  • Shield volcanoes (broad and flat) formed by viscous and slow-moving lava:
  • Volcanic islands + Underwater volcanic ridges
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6
Q

What strength are earthquakes along divergent (constructive) plate boundaries?

A

Earthquakes along divergent (constructive) plate boundaries are weak.

In Iceland:

  • Most are under 3.0
  • Strongest earthquake 17th May 2000 at magnitude 6.5 on Richter scale.
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7
Q

Besides volcanoes, what types of landforms form at divergent (constructive) plate boundaries?

A

Types of landforms at divergent (constructive) plate boundaries:

  • Oceanic ridges
  • Rift valleys
  • Transform faults
  • Fracture zones
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8
Q

Give two examples of landforms on a divergent (constructive) plate boundary:

A

Mid-Atlantic Ridge
Surtsey, Iceland

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9
Q

Draw a diagram of a convergent (destructive) plate boundary:

A

The diagram should feature:

  • Mantle
  • Reference to sub-crustal convection currents
  • Reference to two tectonic plates (Eurasian versus Phillipine Plate for Japan) being pulled together
  • Reference to denser oceanic crust subducting under less dense continental crust
  • Steep composite volcano
  • Ocean trench (gap between plates)
  • Display of magma from end of oceanic crust rising though volcano
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10
Q

What types of volcanoes form at convergent (destructive) plate boundaries?

A

Steep composite volcanoes form at convergent (destructive) plate boundaries, which are tall and have explosive eruptions.

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11
Q

What strength are earthquakes along convergent (destructive) plate boundaries?

A

Earthquakes along convergent (destructive) plate boundaries are fairly strong!

In Japan:

  • The average earthquake strength is 3.76
  • Strongest earthquake 11 March 2011 at magnitude 9.1 on Richter scale
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12
Q

Besides steep composite volcanoes (mentioned on another card), what types of landforms form at convergent (destructive) plate boundaries?

A

Types of landforms at convergent (destructive) plate boundaries:

  • Fold mountains
  • Volcanic cones
  • Volcanic island arcs
  • Ocean trenches
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13
Q

Give two examples of landforms on a convergent (destructive) plate boundary:

A

Mt Fuji (Japan)
Japan Trench (you’ll never guess where ¬_¬ )

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14
Q

Draw a diagram of a transform / conservative plate boundary:

A

The diagram should feature:

  • Two continental plates
  • Arrows showing direction of movement along each other, either opposing or at different speeds.
  • Mantle (underneath diagram)
  • (River bent by fault between the two)
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15
Q

What types of volcanoes form at transform / conservative plate boundaries?

A

Trick question - none! No volcanoes form on transform / conservative plate boundaries as no magma rises.

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16
Q

What strength are earthquakes along transform / conservative plate boundaries?

A

Earthquakes along transform / conservative boundaries are pretty strong!

In the SW USA:

  • There is, on average, a magnitude 6.0 earthquake every 22 years.
  • Strongest earthquake 1907 magnitude ~7.9 on Richter scale.
17
Q

What type of landform forms at transform / conservative plate boundaries?

A

Fault line

18
Q

Give an example of a fault line on a transform / conservative plate boundary:

A

San Andreas Fault, USA (Pacific ^^ vs North American Plate ^ )

19
Q

Draw a diagram of a convergent (collision) plate boundary:

A

The diagram should feature:

  • Mantle
  • Reference to sub-crustal convection currents
  • Reference to two tectonic plates (Eurasian vs Indian for Himalayas, Eurasian vs African for Alps) being pulled together
  • Reference to crumpling / puckling of rocks as they collide
20
Q

What types of volcanoes form at convergent (collision) plate boundaries?

A

Trick question - none! No volcanoes form on convergent (collision) plate boundaries as no magma rises.

21
Q

What strength are earthquakes along convergent (collision) plate boundaries?

A

Earthquakes are infrequent but they can be powerful!

In the Himalayas:

  • Average earthquake strength magnitude 7 on Richter scale (but infrequent)
  • Strongest earthquake 1950 at magnitude 8.7 on Richter scale
22
Q

What type of landform forms at convergent (collision) plate boundaries?

A

Fold mountains

23
Q

Give two examples of fold mountains on convergent (collision) plate boundaries:

A

The Alps, Europe:

  • African Plate→ ←Eurasian plate

Himalayas, Asia:

  • Indian Plate→ ← Eurasian plate
24
Q

How do sea floors spread?

A
  • Rocks partially melt in the upper mantle
  • The resulting magma forms pockets which collect together and rise to the surface
  • Magma is extruded along the ridge
  • Lava cools rapidly in contact with sea water to form new lithosphere, which diverges from the ridge due to sub-crustal convection currents
25
Q

How does fossil evidence support continental drift?

A
  • Similarity of fossils found on matching coastlines of South America and Africa - impossible for the species found to swim across the Atlantic Ocean!
  • Fossils of tropical plants in Antartica suggest that it must have once been situated closer to the Equator where lush-swamp-like flora could grow
26
Q

How do glacial deposits support continental drift?

A
  • Permo-carboniferous glacial deposits in Africa, South America and India suggest that these continents might have been joined when glaciation occured.
27
Q

How do coastlines support continental drift?

A
  • Coastlines match like a jigsaw when fitted together, especially Africa and South America.
  • Orogenic mountain belts of the same age - the Appalacian Mountains, Scottish Highlands and Scandinavian mountains join to create a continuous mountain range when the Atlantic coastlines are fitted together.
  • Precambrian rocks (same age) on either side of the Atlantic also join up when the Atlantic coastlines are fitted together
28
Q

What evidence is there for sea floor spreading?

A
  • Rocks become progressively older with increasing distance from ridge crest
  • Thickness of sediment increases with increasing distance away from the ridge - more time for sediment to accumulate
  • Paleomagnetism - new rock has normal polarity but older rock consists of polarised stripes (same on both sides of the ridge)

Geography A Level (33 decks)

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