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Geography > Earthquakes and volcanoes > Flashcards

Earthquakes and volcanoes Flashcards

1
Q

What the the types of plate boundaries? (3)

A

1) Destructive 2) Constructive 3) Conservative

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2
Q

Destructive plate

A

When oceanic and continental plates move together

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3
Q

What happens on a destructive plate margin?

A

The oceanic plate is forced under the lighter continental plate. Friction causes melting of the oceanic plate and may trigger earthquakes. Magma rises up through cracks and erupts onto the surface

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4
Q

Constructive plate

A

When plates move apart

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5
Q

What happens on a constructive plate margin?

A

Volcanoes are formed as magma wells up to fill the gap, and eventually new crust is formed

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6
Q

Conservative plate

A

Where plates slide past each other in opposite directions, or in the same direction but at different speeds

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7
Q

What happens on a conservative plate margin?

A

Friction is eventually overcome and the plates slip past in a sudden movement. The shockwaves created produce an earthquake

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8
Q

Active volcano

A

Volcanoes, which erupted in the past 80 years

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9
Q

Dormant volcano

A

Resting, but which may erupt again in the feature

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10
Q

Extinct volcano

A

Dead, will not erupt again

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11
Q

What is a plate?

A

A section of earth, which are usually 50 km deep. They include the crust and the mantel

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12
Q

Describe the temperature of the plates and the rocks underneath them

A

The plates are relatively cold, but the rocks underneath them reach 1300C and behave plastically

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13
Q

What physical process moves the plates?

A

Convectional current

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14
Q

How does convectional current work?

A

The mantle at the bottom becomes hot and rises (lower density) it being pushed out by the mantle underneath. The mantel cools down and goes down. The plates move because the mantle underneath them moves

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15
Q

How quickly do the plates move a year? Average

A

1 cm

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16
Q

What happens at plate boundaries (4)

A

More…

1) Earthquakes 2) Volcanoes 3) Mountains 4) Geysers

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17
Q

What comes out of the volcano? (3)

A

1) Gases 2) Liquids 3) Solids

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18
Q

What gases come out of the volcano? (6)

A

1) Water vapour (50%-80%)
2) Sulphur dioxide
3) Hydrogen sulfide
4) Nitrogen
5) Hydrogen
6) Carbon dioxide

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19
Q

Why are the gases dangerous?

A

Some of them are poisonous

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20
Q

Magma

A

Molten rock material below the Earth’s surface

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21
Q

Lava

A

The flows of molten rock material, which has erupted onto the Earth’s surface

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22
Q

What are pyroclastic material?

A

Solids, which come out of the volcano

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23
Q

What solid comes out of the volcano?

A

Ash

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24
Q

What happens when ash goes into the air?

A

It may get suspended in the air, as cloud for months

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25
Q

Describe the size of the ash

A

Small particles less than 4 mm in size

26
Q

Crater

A

A circular depression usually less than 1 km in deameter

27
Q

Vent

A

It is the tube the lava goes up. It leads into the crater

28
Q

Magma chamber

A

Where magma is stored before getting onto the surface

29
Q

Calderas

A

A huge crater caused when a volcanic cone collapses into a partly empty magma chamber after a powerful eruption

30
Q

Parasitic cones

A

These are smaller cones which develop on the sides of a bigger volcano. They are formed when the magma vent becomes blocked

31
Q

Lava domes

A

They form from very viscous lava that is pale colour, and has a high silica content. This lava can’t flow very far before solidifying

32
Q

What are the types of volcanoes? (2)

A

1) Shield

2) Stratovolcanoes

33
Q

Where are shield volcanoes found?

A

Rise from the deep ocean floor

34
Q

Describe the lower and the upper slopes of shield volcanoes

A

Upper slopes - Gentle about 5 deg

Lower slopes - Steeper about 10 deg

35
Q

What are the shield volcanoes composed of?

A

They are composed of long thin lava flows, build up over a central vent

36
Q

Describe the lower, upper slopes and the base of the stratovolcanoes

A

Lower slopes - Steeper slopes 6-10 deg
Upper slopes - Up to 30 deg near the summit
Base - narrow

37
Q

Why does a stratovolcano has steep slopes?

A

Result from short, wide and very viscous lava flows, that don’t travel very far from the vent

38
Q

What is particularly dangerous about stratovolcanoes?

A

They have a long dormant period (thousands of years)

39
Q

Focus

A

A point within the earth where the earthquake occurs

40
Q

Epicentre

A

A point on the Earth’s surface directly above the focus

41
Q

List all the types of waves? (4)

A

1) Transverse
2) Longitudinal
3) Primary
4) Secondary

42
Q

Primary waves

A

Fastest waves, cause back and forth movement

43
Q

Secondary waves

A

Slower waves cause movement from side to side

44
Q

How might the waves cause different types of damage? (3)

A

They move in different directions with different type and power

45
Q

What causes earthquakes?

A

By plates movement, They plates usually get ‘stuck’ in one position. Pressure builds up as the plates try to move . There is sudden release of pressure when plates break free

46
Q

List the types of assessing the damage after an earthquake (2)

A

1) Guiseppi Mercali

2) Richter Scale

47
Q

How does Guiseppi Mercali scale work?

A

It assesses the visible damage using 12 point scale

48
Q

How does Richter Scale work?

A

Measures the total amount of energy released

49
Q

By how many times would the amount of energy increase if the change on Richter Scale was 1?

A

30

50
Q

What factors affect the amount of damaged caused by an earthquake? (5)

A

1) The amount of energy released
2) The depth of focus
3) The density of the population
4) How solid the bedrock is
5) Whether or not the building have been built to withstand earthquakes

51
Q

What happens to the wave speed as the depth of sea decreases?

A

Decreases

52
Q

Tsunami

A

A giant ocean wave or series caused by an earthquake when there is displacement of the seabed

53
Q

What happens to the height of the tsunami waves as it gets closer to the shore?

A

Increases

54
Q

Why can people be evacuated before the tsunami hits the shore?

A

It takes it a long time to move from its epicentre to the shore. It can be seen and the damage can be decreased

55
Q

What is the problem with using Mercalli’s scale?

A

It looks at the effect not the amount of energy released. The damage can differ in different areas because of earthquake resistant building, where as the Richter scale shows the amount of energy which will not be influenced by those factors

56
Q

Seismograph

A

A very sensitive machine, which measures the earth movement

57
Q

Where are the seismographs located? Why?

A

Deep under ground, so that it is not influenced by any other factors

58
Q

Ash fall

A

Ash is blasted into the earth’s atmosphere where it can stay for a long period of time getting away from the volcano and disturbing the air traffic

59
Q

Pyroclastic flows

A

Very hot solid material which can travel very fast down the slopes. Impossible for people to escape from

60
Q

Lateral blasts

A

Sometimes the volcano can explode sideways, which can be destructive for areas within 40km

61
Q

Mudflows

A

Forms when ash gets mixed with water and travels with rivers

62
Q

Volcanic gases

A

CO2 is a dense non-toxic gas, which can flow downhill, causing suffocation

Geography (12 decks)

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