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A level physical geography > Hazards > Flashcards

Hazards Flashcards

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1
Q

define hazard

A

something thats a potential threat to human life or property

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2
Q

What are the types of natural hazard and give examples

A

Geophysical hazards - land processes such as earthquakes

Atmospheric hazards such as cyclones

Hydrological hazards such as floods and avalanches

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3
Q

Define disaster

A

when a hazard actually seriously affects humans

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4
Q

Define risk

A

likelihood of being affected by a hazard

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5
Q

Define vulnerability

A

how susceptible a population is to the damage caused by a hazard

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6
Q

What 5 circumstances affect perception of hazards

A

wealtj
religion
education
past experience
personality

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7
Q

Define hazard incidence

A

How often a hazard occurs

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8
Q

What are the different phases in the park model

A

Pre-disaster
Disruption
Relief
Rehabilitation
Reconstruction

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9
Q

What does the park model show

A

Shows how responses grow during a disaster and help planners predict what resources will be needed at each stage.
For example it also shows that the reconstruction stage is able to improve original conditions

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10
Q

What are the 4 phases of the hazard management cycle

A

Mitigation - minimise impacts of future disasters

Preparedness - planning how to respond to a hazard

Response - how people react when a disaster occurs e.g. evacuation

Recovery - getting the affected area back to normal

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11
Q

Name the layers of the Earth

A

Inner core
Outer core
Mantle
Asthenosphere
Lithosphere
Crust

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12
Q

Describe the inner core

A

solid ball containing iron and nickel 6000C heat from radioactive decay

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13
Q

Describe the outer core

A

Semi-molten and contains lots of iron and nickel

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14
Q

Describe the mantle

A

mostly made of silicate rocks and is quite rigid nearest the core
1000-3500C

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15
Q

Describe the asthenosphere

A

Semi- molten and can flow
made of silicate rocks

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16
Q

Describe the lithosphere

A

silicate rocks and quite rigid 80-90km

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17
Q

Describe the crust

A

There are two types of crust
continental is thicker (30-70km) and less dense
oceanic crust is thinner (6-10km) and more dense

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18
Q

Describe the convection current theory of tectonic movement

A

Circular movement of semi-molten rocks create drag on the base of the tectonic plates causing them to move

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19
Q

Describe the slab pull theory of tectonic movement

A

At destructive plate margins denser crust is forced under less dense crust and the sinking of the plate edge pulls the rest of the plate towards the boundary

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20
Q

Describe the ridge push theory of tectonic movement

A

At constructive plate boundarys magma rises to the surface and forms new crust which is very hot and heats surrounding rocks which expand and rise forming a slope

The new crust cools and becomes denser causing the denser rock to move downslope away from the plate margin puts pressure on the tectonic plates causing them to move apart

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21
Q

What are three theories of tectonic movement

A

Convection currents
slab pull
ridge push

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22
Q

Describe constructive/divergent plate margins

A

occur where two plates move apart

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23
Q

What events can occur at constructive plate margins

A

Volcano
earthquake
Ocean ridge
Rift valley

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24
Q

Describe how a volcano occurs at a constructive plate margin

A

pressure is released at the margin causing the mantle to melt producing magma which rises as it is less dense and can reupt to form a volcano

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25
Q

Describe how an earthquake occurs at a constructive plate margin

A

Plates dont move apart uniformly, some parts move faster tha others causing pressure to build up and when the pressure become too much the plate cracks making a fault line and causing an earthquake

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26
Q

Describe the formation of an ocean ridge

A

Diverging plates underwater cause underwater volcanoes to erupt along mid-ocean ridges and they can build up to be above sea level for example Iceland

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27
Q

Describe the formation of a rift valley

A

Where plates diverge beneath land rising magma causes the continental crust to bulge and fracture forming fault lines

As the plates keep moving apart the crust between parallel faults drops down to form a rift valley for example the East African rift system

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28
Q

Describe destructive/convergent plate margins

A

Where two plates are moving towards each other

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29
Q

What events/landforms can occur at destructive plate boundaries

A

deep sea trench
fold mountains
volcanoes
earthquakes
Island arcs

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30
Q

Describe what occurs at an oceanic - continental destructive plate margin

A

oceanic crust is forced under the less dense continental crust which forms a deep sea trench

Fold mountains also occur where the plates meet as the accumulated sediment on the continental crust is folded upwards along with the edge of the continental crust

oceanic crust is heated and turns into magma and will rise to the surface to form volcanoes

Plates can get stuck when they subduct and when the pressure gets too much they jerk past each other and cause an earthquake

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31
Q

Describe what occurs at an oceanic-oceanic destructive plate margin

A

The denser plate of the to will be subducted forming a deep sea trench and triggering earthquakes and volcanic eruptions

Volcanic eruptions that take place underwater can form island arcs

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32
Q

Describe what occurs at a continental-continental destructive plate margin

A

when two continental plates move towards each other neither is subducted so there aren’t any volcanoes but the pressure build up between them can cause earthquakes

Fold mountains form here

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33
Q

Describe what occurs at a conservative plate margin

A

Two plates are moving past each other

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34
Q

Describe the events that occur at a constructive plate margin

A

2 Plates get locked together and in places pressure build up causing the plates to jerk past each other releasing the energy as an earthquake e.g. the Pacific and N.American plates

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35
Q

What is a fold mountain and how do they form

A

made of sediments that have accumulated on the continental crust which are folded upwards along with the edge of the continental crust e.g. Himalayas

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36
Q

Describe how an island arc is formed

A

A magma plume rises up from the mantle and remains stationary but the crust moves above it and new volcanoes form in the part of the crust now above the magma plume e.g. hawaii

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37
Q

Describe the types of volcanoes that form at constructive margins

A

fissure and shield
Basaltic lava is formed here

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38
Q

Describe basaltic lava

A

it is very hot and has a low viscosity so it flows easily
Eruptions are frequent but effusive

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39
Q

Describe how a volcano forms on a constructive boundary

A

If the boundary is underwater magma rises to fill the space left by plates moving part forming ocean ridges

if the boundary is on land as plates pull apart forming rift valleys they become thinner and magma is able to break through the surface

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40
Q

What type of volcanoes form at destructive boundaries

A

Composite and caldera
rhyolitic and andesitic lava is formed here

41
Q

Describe rhyolitic and andesitic lava

A

Cooler and more viscous so they flow less easily and they have a higher silica content
the eruptions are less frequent but more explosive

42
Q

Describe how volcanoes form at destructive margins

A

At subduction zones where one plate is pulled under the other the melting of the plate forms magma which rises to the surface as volcanoes, because the lava is so viscous it forms blockages in volcanic vents causing pressure to build

43
Q

What are some primary volcanic hazards?

A

Nuee ardente
lava flows
volcanic gases
pyroclastic and ash fallout

44
Q

Describe nuees ardentes

A

A mixture of super-heated gas ash and volcanic rock that flows down the side of a volcano at a high speed and long distance (80km/h) (10-15km)

45
Q

Describe lava flows

A

The speed of the lava flow and distance travelled depend on the temperature and viscosity of the lava as well as the steepness of the slope
Low viscosity lava can flow at up to 10km/h on a steep slope and may travel 10s of kilometres

46
Q

Describe volcanic gases

A

Lava contains gases such as carbon dioxide and sulfur dioxide which are released into the atmosphere after a volcano explodes which can be harmful to o organisms if breathed in

47
Q

Describe pyroclastic and ash fallout

A

Pyroclastic fallout is material that has been ejected from a volcano during an eruption and falls back to the ground and ash fallout consists of mostly gas

Fallout consists of material of a range of sizes from large rock weighing several tonnes to ash particles

Large pieces of falling tephra can damage infrastructure

48
Q

What are the secondary hazards of a volcano

A

Lahars
acid rain

49
Q

Describe lahars

A

they occur when volcanic material mixes with large amounts of water e.g. ice melt and flows very quickly (over 80km/h) and can travel for 10s of kilometres

50
Q

Describe acid rain

A

Volcanic gases can react with water vapour in the atmosphere which then falls as acid rain and can damage buildings and ecosystems

51
Q

Describe how the magnitude of a volcano can be measured

A

Volcanic events can be measured using the volcanic explosivity index which grades volcanoes on a scale of 0-8 based on the amount of material ejected

52
Q

Describe how earthquakes are formed

A

Caused by tension that builds up at all three plate boundaries, when the plates jerk past each other it sends out shockwaves

53
Q

Define focus

A

Near the focus the shockwaves are stronger
Origin

54
Q

Define epicentre

A

point on Earths surface where the earthquake is felt first
directly above focus

55
Q

What scales are used to measure earthquakes

A

The richter scale
moment magnitude scale
Mercalli scale

56
Q

Describe the Richter scale

A

Measures the magnitude of an earthquake and is logarithmic

57
Q

Describe the moment magnitude scale

A

based on the total amount of energy released from an earthquake and is also logarithmic and more accurate than the richter scale

58
Q

Describe the Mercalli scale

A

Measures the impacts of an earthquake using observations of the event with a scale between 1-12

59
Q

What are some seismic hazards

A

Earthquakes
Landslides and avalanches
Tsunamis
Soil liquefaction

60
Q

Describe how tsunami is formed

A

Large waves cause by the displacement of large volumes of water which can be triggered by underwater earthquakes
A tsunami will usually be more powerful closer to the coast

61
Q

Describe landslides and avalanches

A

shaking of the ground can often dislodge rock or snow and cause them to move downslope quickly

Shaking can also loosen ground making it easier for water to infiltrate which may trigger a landslide even when shaking has stopped due to the extra weight

62
Q

Describe soil liquefaction

A

When soil is saturated with water the vibrations of the earthquake can cause it to act like water making it weaker and easier to deform so its more likely to subside

63
Q

Describe how margin type affect the nature of an earthquake

A

The biggest earthquakes occur at destructive plate margins and those at constructive tend to be of a lower magnitude

64
Q

Describe how rate of movement can affect the nature of an earthquake

A

No clear relationship

65
Q

Describe how the depth of focus affects the nature of an earthquake

A

Deep focuses tend to be of a higher magnitude than shallow focus earthquakes however deep focus earthquakes tend to do less damage

66
Q

Describe how tropical storms form

A

A disturbance near the sea surface triggers the storm e.g. an area of low pressure

Sea water thats warm (above 27C at least 50m below the surface)

A convergence of air in the lower atmosphere ( boundary between warm and cold air this forces warm air to rise)

location at least 5 from the equator because the coriolis effect is stronger further away from the equator

67
Q

what happens when tropical stoms reach land

A

they lose energy

68
Q

describe the structure of a tropical storm

A

they are circular and hundreds of kilometres wide and usually last 7-14 days

The eye is very low pressure and rising air spirals in eyewall causing strong winds

Near the top of the storm there is an outflow of moisture laden air

69
Q

how is storm strength measured

A

using the Saffir-Simpson scale
based on wind speed and estimating damage caused

70
Q

How can a tropical storm be followed

A

cloud formation can be identified from satellite imagery and used to tell when a tropical storm is forming and be tracked

71
Q

what are the 3 types of wildfire

A

ground fire
surface fire
crown fire

72
Q

describe crown fire

A

where the ground itself burns
it is a slow smouldering fire with no flame and little smoke

73
Q

describe surface fire

A

where leaf litter and low lying vegetation burn
fire can be low or high intensity

74
Q

Describe crown fire

A

Where fire moves through the canopy
fires are likely to be intense and fast moving

75
Q

what conditions affect intensity of wildfires

A

vegetation
fuel characteristics
climate and weather
fire behaviour

76
Q

describe how vegetation type can cause intense wildfires

A

thick undergrowth
closely spaced trees
trees such as pine that contain a lot of oil

77
Q

describe how fuel characteristics can cause intense wildfires

A

fine dry materials
large amount of fuel with continuos cover

78
Q

describe how climate and weather can favour intense wildfires

A

rainfall must be sufficient for fuel growth
dry season
strong winds

79
Q

Describe how fire behaviour can favour intense wildfires

A

a running fire is more rapid than a creeping fire

80
Q

describe the natural causes of wildfires

A

lightning in absence of rain
volcanic eruptions

81
Q

what are the human causes of wildfire

A

dropping cigarettes
arson
uncontrolled bbq and bonfire
sparks from fireworks

82
Q

what are the types of perception of a hazard

A

fatalism
adaptation
fear

83
Q

define fatalism

A

losses are accepted as inevitable and people remain where they are

84
Q

define adaptation

A

belief that survival is viable due to prediction prevention and protection

85
Q

define fear

A

people feel vulnerable to a hazard and move away

86
Q

define community resilience

A

sustained ability of a community to utilise available resources to respond withstand and recover from effects of a natural hazard

87
Q

what management system do many governments use

A

integrated management risk which incorporates identifying a hazard analysing the risk and establishing priorities

88
Q

why might people put themselves at risk from a hazard

A

hazard unpredictability
lack of alternatives
changing risk level
cost/benefit

89
Q

how are hazards mainly managed

A

prediction, prevention, protection

90
Q

what does the risk management cycle illustrate

A

the ongoing process which governments plan and reduce the impact of disaster reacting during and immediately after an event

appropriate actions at all points can lead to greater preparedness

91
Q

what is one of the main goals of the risk management cycle

A

promotion of sustainable livelihoods because people then have greater capacity to deal with disasters and recovery is rapid and long lasting - used by FEMA

92
Q

what could the difference in recovery periods be due to

A

related to the types of hazard, degree of preparedness, speed of relief effort, nature of recovery and reliability

93
Q

describe the theory of crustal evolution

A

states that the lithosphere is able to slide over the asthenosphere and this allows plate movement evidence supporting this main theory is that oceanic crust is slowly moving away from plate boundaries and it gets older with distance

94
Q

define palaeomagnetism

A

magnetic signatures of the rocks on the ocean floor

95
Q

how does palaeomagnetism support the theory of plate tectonics

A

patterns of opposite directions of magnetic fields were discovered this shows that magma rises from the ridges in the ocean floor and forms new rock recording a more recent alignment of magnetic fields pushing old rock with more outdated magnetic field further from the ridge

96
Q

what is the theory of plate tectonics

A

Alfred Wegner suggested that continents have moved into their current positions from Pangea through the process of continental drift

97
Q

what is the geological evidence that supports the theory of plate tectonics

A

continental fit coast of S.America and west coast of Africa

glacial deposits 290m years ago found in India, antarctica and south America

matching rock sequences in Scotland and Canada

98
Q

What is the biological evidence for the the theory of plate tectonics

A

fossils found in india and Australia of similar species

Mesosaurus fossils found in south America and south Africa

plant fossils found in antarctica and india meaning they’re climates were similar at some points

99
Q

describe sea floor spreading and its evidence

A

mid-atlantic ridge
alternating polarity of rock
age of rock

A level physical geography (3 decks)

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