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A Level Geography > hazards > Flashcards

hazards Flashcards

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1
Q

4 layers of the earth

A

inner and outer core, mantle and crust

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2
Q

whats the lithosphere

A

crust and upper-most solid mantle

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3
Q

whats the asthenosphere

A

lies beneath the lithosphere, this layer is semi-molten which the plates float and more

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4
Q

how thick is the oceanic crust

A

6-10km

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5
Q

how thick is the continental crust

A

30-70km

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6
Q

what was pangea and who founded it

A

alfred wegener published a theory in 1912 that a single continent existed 300 million years ago

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7
Q

what were the north and south of pangea called

A

north- laurasia
south- gondwanaland

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8
Q

geological evidence for pangea theory

A
  • the fit of south america and west africa
    -evidence of late carboniferous glaciation, deposits from which are found in south america , antarctica and india
  • striations on rocks in brazil and west africa
  • rock sequences in northern scotland closely agree with those found in eastern canada indicating they were laid down under the same conditions
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9
Q

biological evidence for pangea theory

A
  • fossil brachiopods found in indian limestone are comparable with similar fossils in australia
    -fossil remains of the reptile mesosaurus are found in both south america and southern africa, it is unlikely that the same reptile could have developed in both areas or that it could have migrated accross the pacific
  • the fossilise remains of a plant which existed when coal was being formed have been located only in india and antarctica
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10
Q

what was wegeners theory unable to explain

A

continental movement, so when the mid-atlantic ridge was discovered sea-floor spreading was occcuring, so subduction must be occuring elsewhere

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11
Q

whats ridge push

A

when plates move apart ( constructive boundary) the magma rises from the mantle. it creates new hot and dense rock, it pushes the old rock out the way creating a ridge in the crust ( also called gravitational sliding )

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12
Q

slab pull

A

gravity pulls the old rock into the mantle because the rock has become colder and denser, this occurs at subduction zones in destructive boundaries

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13
Q

where are hotspots and magma plumes located

A

located along the plate boundaries and alot of them are along the mid-atlantic ridge. however there are a few hot spots in the centre of the pacific plate which are not along the plate boundary

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14
Q

how are hotspots formed

A

radioactive decay within earth core generates very hot temps
-if decay is conc hotspot forms
-hotpsot heat lower mantle creting localised thermal currents where magma plumes rise
- these plumes sometimes cause volcanic activity in the middle of plate boundaries
-can form islands such as hawaiian islands

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15
Q

physical causes of earthquakes

A

on plate boundary margins
some occur away from plate boundaries and are associated with the reactivation of old fault lines eg uk

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16
Q

human causes of earthquakes

A

buildings of large reservoirs
deep mining
fracking

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17
Q

whats the focus

A

the point at which pressure is released within the earths crust

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18
Q

whats the epicentre

A

the point on the earth surface immediately above the focus. this is where the earthquake is felt and where the most intense ground shaking takes place

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19
Q

how deep is a shallow focus

A

0-70km

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20
Q

how deep is a intermediate focus

A

70-300km

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21
Q

deep focus

A

300-700km

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22
Q

4 different types of shock waves

A

primary/pressure waves
secondary/shear waves
surface/love
rayleigh

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23
Q

3 scales in which earthquakes are measured

A

richter scale
mercalli scale
moment magnitude scale( mms)

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24
Q

mercalli scale

A

this measures how much damage is caused by observations
measured on a scale between I AND XII
good for insurance purposes

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25
Q

primary impacts of earthquakes

A

ground shaking of which the severity depends upon the magnitude, depth, distance from epicentre and local geological conditions
ground rupturing wich is a visible breaking/displacement of earths surface, poses a threat to large structures such as dams brides and nuclear systems

26
Q

secondary impacts of earthquakes

A

solid liquefaction
landslides/avalanches
tsunamis
fires
destroyed infrastructure

27
Q

whats soil liquefaction

A

when vibrations/water pressure within a solid cause soil to loose contact with other particles. as a result soil behaves like a liquid and has an inability to support weight
causes lack of access meaning aid cant get to people quickly

28
Q

whats a tsunami

A

giant sea waves generated by shallow-focus underwater earthquakes involving movements of the sea bed, or landslides into the sea

29
Q

whats the first warning of a tsunami

A

the wave trough in front of the tsunami which results in a reduction in sea levels , known as drawdown

30
Q

what percentage of tsunamis are generated in the pacific basin

A

90%

31
Q

when was tohoku region of japan earthquake

A

2011

32
Q

what was the magnitude of japan earthquake of 2011 and how far offshore was it

A

magnitude of 9 , 70km offshore

33
Q

how many death in japan earthquake/tsunami of 2011

A

nearly 16000

34
Q

how far inland did japan tsunami of 2011 reach

A

10km

35
Q

what nuclear power plant was shut down in japan tsunami 2011

A

fukashima

36
Q

primary effects of wildfires

A

smoke
loss of vegetation and crops
loss of life and injury to people and animals
destruction of property and possesions

37
Q

secondary effects of wildfires

A

health problems from smoke inhalation
loss of animal habitats, homelessness, increased soil erosion, insurance premiums rise, access to recreational areas is restricted

38
Q

peoples circumstances on their perception of hazards

A

wealth, religion, education, past experiences, personality

39
Q

what is risk sharing

A

involves sharing the cost of reducing a hazard, the benefits of preventing it or the costs of not preventing it- eg people buy insurance to help them repair their property after a disaster. most people wont be affected by an event so they wont claim insurance- this means lots of people contribute so the cost is shared

40
Q

fatalism

A

some people believe hazards cannot be avoided so they must just be accepted

41
Q

what does the park model show

A

shows how responses progress during a disaster, which may help lanners predict what resources will be needed at each stage
pre-disaster, disruption, relief, rehabilitation, reconstruction. line graph. can help planners to prepare for future hazards.

42
Q

hazard management cycle

A

4 stages- mitigation, preparedness, responce, recovery. its a cycle because hazards keep happening so efforts to prepare for them or mitigate their effects are ongoing

43
Q

what is the core made u of

A

iron and nickel

44
Q

what is the mantle made up of

A

mostly silicate rocks

45
Q

convection currents

A
  • mantle is hottest close to the core so lower parts of the asthenosphere heat up and become less dense and begin to rise
  • as they move towards the top of the asthenosphere they cool down become more dense and slowly sink.
  • this creates a drag on the base of the tectonic plates causing them to move
46
Q

sea-floor spreading

A

as tectonic plates diverge( move apart) magma rises to fill the gap, then cools and forms new crust.
-over time new crust is dragged apart and more crust formed and the sea floor gets wider.
- creates structures called mid-ocean ridges of higher terrain on either side of the margin

47
Q

constructive margins

A

occurs when 2 plates are moving apart (diverge). the mantle is under pressure from the plates above. when they move apart the pressure is released which causes the mantle to melt , producing magma ( forming volcano ). if plates dont move apart in uniform way the pressure is too much and the plate cracks forming an earthquake

48
Q

rift valley

A

where plates diverge beneath land, as the plates keep moving apart the crust between the parallel faults drops down to form a rift valley. eg east African rift system, a series of valleys that stretch 4000km from Mozambique to the red sea. volcanoes such as mt kilimanjaro and mt kenya can be found around rift valleys

49
Q

destructive margins (oceanic- continental)

A

move towards each other( converge ), more dense oceanic crust forced under the continental crust ( its subducted ). forms deep sea trenches, eg Peru-Chile trench in the pacific ocean. FOLD MOUNTAINS also formed here- made up of sediments that have accumulated on continental crust which are folder upwards. VOLCANOES also formed as oceanic crust melted by mantle and magma rises. when the pressure builds up as they subduct EARTHQUAKES are also created.

50
Q

destructive margins ( oceanic-oceanic )

A

most of the same processes occur, the denser of the 2 is subducted forming deep sea trenches and triggering earthquakes and volcanic eruptions. islands arcs like mariana islands are formed by underwater volcanic eruptions

51
Q

conservative plate margins

A

Earthquakes occur here as plates get locked together and pressure builds up. Fault lines also form as plates moves past each other, eg Sam Andrea’s fault

52
Q

Primary hazards of volcanoes

A

Pyroclastic flow, lava flow , volcanic gasses , ash fallout and tephra

53
Q

Pyroclastic flows

A

Cloud of super-heated gas, ash, volcanic rock

54
Q

Lava flow

A

Speed and instance depends on viscosity

55
Q

Volcanic gasses

A

CO2 sulphur dioxide

56
Q

Ash fallout and tephra

A

Any rock / ash material

57
Q

Secondary hazards

A

Lahars , acid rain

58
Q

Lahars

A

Mudflow, volcanic materials mix with water

59
Q

Short term responses to hazards

A

Evacuation , exclusion zones, emergency shelter and supplies

60
Q

Long term

A

Strengthened buildings , tourism , monitoring systems , shelter, education

61
Q

Moment magnitude scale

A

Based on total amount of energy released, logarithmic,, more accurate than richter

62
Q

Conditions for storms

A

50 m deep water, 26.5c , coriolis effect , disturbance near surface such as low pressure

A Level Geography (9 decks)

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