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Geography > The restless earth > Flashcards

The restless earth Flashcards

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1
Q

what are the layers of the earth called

A

crust
mantle
outer core
inner core

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2
Q

crust

A

the outer layer of the earth

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3
Q

plate

A

a section of earths crust

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4
Q

plate margin

A

the boundary where two plates meet

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5
Q

mantle

A

the dense, mostly solid layer between the outer core and the crust

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6
Q

convection current

A

the circular currents of heat in the mantle

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7
Q

what are the characteristics of oceanic crust

A

newer most less then 200 million years old
denser
can sink
can be renewed and destroyed

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8
Q

what are the characteristics of continental crust

A

older most over 1500 million years old
less dense
cannot sink
cannot be renewed or destroyed

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9
Q

what causes plates to move

A

convection currents

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10
Q

subduction

A

sinking of oceanic crust at a destructive margin

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11
Q

collision

A

meeting of two plates of continental crust. They are both the same type so they meet ‘head on’ and buckle

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12
Q

diagram of destructive plate margin see page 10

A 
/| |\
                         /  | |  \
                        /   | |    \
oceanic plat /     | |      \
\_\_\_\_\_\_\_\_\_\_      | |  \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_
           ------->     \
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13
Q

describe a destructive plate margin

A

plates move together

oceanic goes under continental causes subduction

oceanic plate melts and causes pressure and chemical reactions cause volcanic reaction

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14
Q

describe a constructive plate margin

A

plates moving apart from each other

usually happens under the oceans

as plates move away from each other and cracks and fractures from between the plates where there is no solid crust

magma forces way up between cracks causing volcanos and volcanic islands

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15
Q

describe a conservative plate margin

A

plates sliding past each other

they move at a slightly different angle to each other

one moves slightly faster

plates build up pressure till they are suddenly released causing an earthquake

crust is neither created or destroyed

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16
Q

how are all mountain produced and what are they called

A

fold mountains
result from plates of the same type moving towards each other
causing sediment deposited on ocean floor to buckle

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17
Q

what are the two types of volcano

A

composite

shield

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18
Q

what is a composite volcano

A

a steep sided volcano that is made up of a variety of materials such as lava and ash

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19
Q

what is a shield volcano

A

a broad volcano that is mostly made up of lava

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20
Q

what are fold mountains

A

large mountain range where rock layers have been crumpled as they have been forced together

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21
Q

what is a ocean trench

A

deep sections of the ocean, usually where an oceanic plate is sinking below a continental plate

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22
Q

add Sweden use of a mountain range

A

do it

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23
Q

what is the distribution of volcanoes

A

their spread relates closely to plate margins

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24
Q

name a country which utilises fold mountains

A

Switzerland

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25
Q

How were the fold mountains in the Swiss Alps formed

A

from the collision of the African and European plates 40 million years ago

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26
Q

how much of Switzerland is mountainous

A

70%

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27
Q

how many people live in Switzerland

A

8 Million

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28
Q

how does Switzerland make use of the fold mountains

A

1) Over 40 ski resorts
2) Tourism provides 150,000 full time jobs
3) over 8 million people visit annually (more then the population)
4) ranked 25th in the world in terms of visitors numbers
5) 3% of the swiss economy from tourism
6) tourism helps fund the country’s transport system
7) 200 km national park created promoting eco tourism

29
Q

how has Switzerland tried to be sustainable

A

1) fast flowing glacial lakes used for HEP power plants and now have 550 HEP power plants
2) 70% of Switzerlands power is from HEP power plants

(HEP hydroelectricity power)

30
Q

natural hazard

A

An occurrence over which people have little control, which poses a threat to peoples lives and possessions. This is different from a natural event as volcanoes can erupt in unpopulated areas without being a hazard

31
Q

Primary effect

A

The immediate effects of the eruption caused directly by it

32
Q

secondary effects

A

the after-effects that occur as an indirect effect of the eruption on a longer timescale

33
Q

aid

A

Money, food, training and technology given by richer countries to poorer ones, either to help with an emergency or to encourage long-term development

34
Q

where is Mount St Helens located

A

it is one of 5 volcanoes located in the cascade range in Washington State USA

35
Q

when where the first signs that Mt St Helens was going to erupt

A

March 1980

36
Q

how big was the exclusion zone around Mt St Helens

A

8km

37
Q

when did Mt St Helens erupt

A

8:32 am 18th May 1980

38
Q

how big was the earthquake when Mt St Helens erupted

A

5.1 on the Richter scale and caused largest land slide ever recorded

39
Q

how big was the earthquake when Mt St Helens erupted

A

5.1 on the Richter scale and caused largest land slide ever recorded

40
Q

how big was the destruction caused by Mt St Helens

A
  1. All living things 27km north of the crater wiped out

2. 57 people died

41
Q

earthquake

A

A sudden and often violent shift in the rocks forming the earth’s crust, which is felt at the surface

42
Q

immediate responses

A

how people react as the disaster happens and in the immediate aftermath

43
Q

Long term Responses

A

Later reactions that occur in the weeks, months and years after the event

44
Q

give some primary impacts of Mt St Helens eruption

A

1) 150 mils sq of forest flattened in 6 minutes
2) height of mountain reduced by 1300 ft
3) 7000 big game (deer, elk) killed along with 12 million young fish
4) 30 bridges, 200 homes, 200 miles of road and 15 miles of railway track destroyed
5) 57 people killed and tourists left stranded
6) ash fell as far as 900 miles away- breathing was difficult
7) lateral blast and rock slide on half a cubic mile of rock
8) explosion equivalent to 20 million tonnes of TNT

45
Q

give some secondary impacts of Mt St Helens eruption

A
  1. volcanic ash could spread across USA within 3 days
  2. ash fell as far as 900 miles away
  3. rivers became filled with ash from lahars several days later
  4. major disruption to transportation and communication networks for many weeks/ months.1 bil US$ in damage
    5 disaster tourism grew in the years that followed eventually increasing revenue from 3 million tourists
  5. large scale destruction to the national park area and a severe reduction in tourism
  6. ash long term help to improve fertility of the soils in the region
46
Q

what were the immediate and long term responses of Mt St Helens eruption

A
  1. 8km exclusion zone put around volcano after scientists became weary of a possible explosion
  2. 1m deep piles of ash on roads cleared within 3 days
  3. forests to the northern flank of the volcano were replanted
  4. rebuilding of bridge and roads took place. improved monitoring of volcanoes I region by building the cascade observatory
  5. 2 million face masks provided by US government to aid with ash problems
  6. after explosion, helicopters mobilised for search and rescue mission
  7. residents evacuated prior to explosion
47
Q

vent

A

the opening-usually central and single - in a volcano from which magma is emitted

48
Q

Lahar

A

these secondary effects of a volcanic eruption are mudflows resulting from ash mixing with melting ice or water

49
Q

list the 3 steps that form a supervolcano

A
  1. rising magma cannot escape and a large bulge appears on the surface
  2. cracks appear in the surface and gas and ash erupt form the magma chamber
  3. the magma chamber collapses, forming a depression called a caldera
50
Q

Supervolcano

A

a mega colossal volcano that erupts at least 1000km of material

51
Q

caldera

A

the depression of the supervolcano marking the collapsed magma chamber

52
Q

fissures

A

extended openings along a line of weakness that allow magma to escape

53
Q

geothermal

A

water that is heated beneath the ground, which comes to the surface in a variety of ways

54
Q

geyser

A

a geothermal feature in which water erupts into the air under pressure

55
Q

Hot spot

A

a section of the earth’s crust where plumes of magma rise weakening the crust These are away from plate boundaries

56
Q

what happened last time a supervolcano erupted

A

74,000 years ago Toa erupted and world temperatures fell by 3 - 5 c and 3,000 km of covered magma covered India in 15cm of ash

57
Q

list 3 differences between a volcano and a super volcano

A

1) caldera
2) 1000x more material
3) occur at hotspots

58
Q

earthquake

A

a sudden and brief period of intense ground shaking

59
Q

focus

A

the point in the earth s crust where the earthquake originates

60
Q

Richter scale

A

a logarithmic scale used for measuring earthquakes based on scientific recordings of the amount of movement

61
Q

epicentre

A

The point at the earth’s surface directly above the focus

62
Q

shockwaves

A

seismic waves generated by an earthquake that pass through the earth’s crust

63
Q

mercalli scale

A

a means of measuring earthquakes by describing and comparing the damage done, on a scale of I to XII

64
Q

what are longitudinal waves

A

waves cause up and down movement

65
Q

what are transverse waves

A

waves cause side to side movement which causes much damage

66
Q

what are primary waves

A

travel fastest, causing back and forth movement

67
Q

what are secondary waves

A

travel slower and cause movement from side to side

68
Q

how does the Richter scale

A

starts at 1 and is no cap on size

a 2 earthquake is 10x bigger then a 1 and 3 is 10x bigger then a 2 etc

69
Q

where do earthquakes normally occur

A

destructive or collision or conservative plate boudries

Geography (2 decks)

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