Physical Geography > Hazards > Flashcards

Hazards Flashcards

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1
Q

What is a hazard?

A

A potential threat to human life and property caused by an event

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2
Q

What does Deggs model show?

A

A disaster only occurs when a hazardous event is combined with a vulnerable population

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3
Q

What are the 3 types of hazards?

A

Geophysical, atmospheric, hydrological

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4
Q

why do some people live near hazards

A
  • hazards are unpredictable
  • lack of alternatives due to socio-economic and political factors
  • environmental benefits such as fertile soil and climate
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5
Q

ways perceptions of hazards could be changed

A
  • level of education
  • religion / culture
  • socio-economic status
  • employment status
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6
Q

Risk

A

Likelihood that humans will be seriously affected

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7
Q

Vunerability

A

How susceptible a population is to the damage caused

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8
Q

Fatalism

A

The viewpoint that hazards are uncontrollable and losses should be accepted

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9
Q

Adaptation

A

Adjusting our behaviour accordingly so losses can be kept minimum

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10
Q

Domination

A

Using scientific research and technology to predict, mitigate and control hazards

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11
Q

What are the 4 phases of the hazard management cycle?

A

Preparedness, response, recovery, mitigation

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12
Q

advantages of HMC

A
  • highlights imporatance of mitigation + preparedness (not just aftermath)
  • helps governments organise plan response clearly
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13
Q

disadvantages of HMC

A
  • doesn’t show scale of impact or recovery differences
  • assume countries have recources to implement all stages
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14
Q

What are the 4 phases of Park’s model?

A

Pre disaster, relief, rehabilitation, reconstruction

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15
Q

adavnatges of the park model

A
  • better for undertsanding differences in scale of imact
  • focuses on response
  • simple + visual
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16
Q

disadvantages of park model

A
  • assumes recovery is smooth + predictable
  • ignores inequality
  • doesn’t condiser secondary hazards
  • doesn’t account for spatial variability
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17
Q

Features or oceanic crust

A

thinner (5-10km), denser, younger

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18
Q

Features of contintental crust

A

Thicker (up to 70km), less dense, older

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19
Q

Asthenosphere

A

Zone within the upper mantle, situated beneath the lithosphere, semi molten layer

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20
Q

Lithosophere

A

Rigid upper layer of mantle and crust

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21
Q

Mantle

A

Semi molten layer, widest layer (2900km), high temperatures

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22
Q

Core

A

Inner core - solid centre, mostly composed of iron
Outer core - semi molten, mostly iron and nickel

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23
Q

what did alfred wegener believe

A

Suggested earths continent had once been sort of a single landmass called Pangea, they gradually drifted apart over millions of years of years

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24
Q

Convection currents

A

Circular motion of semi molten rock. Hot, less dense mantle material rises and cooler, denser material sinks, creating currents.

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25
what drives convection currents
radioactive decay
26
slab pull
As oceanic plate sinks at a subduction zone, gravity pulls the plate down into the mantle
27
Ridge push
At constructive boundaries, crust moves away from a mid oceanic ridge, it cools and becomes denser and thicker, slipping down. Gravity pulls the lithosphere down this slope
28
Sea flore spreading
New oceanic crust moves away from the ridge, pushing older crust further from the ridge.
29
geological evidence for continental drift
- jigsaw fit between continents e.g South America and West Africa - similar glacial deposits in sotuh africa, india and antartica - similar rock sequences in north scotland and east canada
30
biological evidence for continental drift
- fossils in india are similar to those in Australia - identical plant fossils in india and antartica
31
what is paleomagnetism
the study of the record of Earth’s magnetic field preserved in rocks
32
how does paleomagnetism provide evidence for seafloor spreading
provides evidence for seafloor spreading through symmetrical, alternating magnetic "stripes" of normal and reversed polarity on the ocean floor, reflecting the earths magnetic reversals
33
contsructive margins have...
shield volcanoes, earthquakes, oceanic ridges, rift valley
34
How do volcanoes form at constructive margins
plates move apart, pressure on the mantle is reduced, causes mantle to melt and produce magma. magma is less dense than surrounding rock so rises through cracks + fissures. magma then cools + solidifies to form new basaltic rock.
35
How do rift valleys form at cconstructive margins
plates move apart, crust stretches + becomes weaker. cracks/fault lines form. Crust breaks into blocks, some drop down between parallel faults
36
destructive margins have...
deep sea treches, fold mountains, earthquakes, destruvtive volcanoes, island arcs,
37
How do volcanoes form at destructive margins
denser oceanic plate subducts beneath the continental plate into the mantle. Heat and pressure causes the plate to melt forming magma. magma rises through cracks and fissures
38
how do island chains like hawaii form
A fixed plume of magma melts as plate moves above creating volcanoes that build up from the ocean floor.
39
shield volcanoes (type of lava and destription of eruptions)
baslatic lava eruptions are frequent + last long not very violent
40
features of basaltic lava
- very hot (1000–1200°C) - low viscosity = runny - low in silica - fast moving
41
composite volcanoes (type of lava and description of eruption)
andesitic lava eruptions are not as often more violent erutions
42
features of andesitic lava
- moderate temperature (800–1000°C) - high viscosity = thick - higher silica levels - slow moving
43
Hawaiin eruptions
- basaltic lava - gentle - lava flows gently from a central vent, shiel volcanoes
44
Strombolian eruptions
- basaltic/andesitic lava -moderate explosivity - frequnt eruptions of tephra + steam. occasional lava flows
45
vulcanian eruptions
- andesitic, rhyolitic, basaltic - violent - less frequent + more violent. gas, ash, tephra, composite volcanoes
46
Plinian eruptions
- rhyolitic lava - catastrophic violent eruptions of gases and ash columns
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pyroclastic flows
mixture of super heated gas, ash + volcanic rock travels at high speeds
48
Lava flows
most are slow + viscous - people have time to evacuate destroys everything
49
Volcanic gases
lava contains gases such as CO2 + sulfur dioxide can be harmful if breathed in
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tephra + ash fallout
large pieces can damage buildings + kill/injure finer pieces can kill vegeteation, hinder roads + rail
51
Lahars
volcanic material that mixes with water moves very quicly + travels very far destroys settlemets, habitats
52
Acid rain
volcanic gases can react with water vapour harmful to habitats deteriorate stones + metal
53
what are 3 signs a volcano may erupt
1. an increase in the release of volcanic gases 2. a rise in the level of lava lakes in the crater 3. the buldging up of surrounding land due to pressure
54
How does an earthquake occur
As the crust of the Earth is constantly moving, there tends to be a slow build up of stress within the rocks. WHen this pressure is released, parts of the surface experience a short intense shaking motion
55
focus
the point at which the pressure is released within the crust
56
epicentre
the point on the surface directly above the focus
57
Primary (p) waves
- Fastest wave + reach surface first - longitudinal - travel through both mantle and core
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Secondary (s) waves
- half as fast, reach surface after p - transverse - travel through mantle, not core
59
Surface Love (L) waves
slowesr waves cause the most damage
60
Richter scale
- logarithmic scale from 1-10 - measures magnitude
61
Moment magnitude scale
- logarithmic scale from 1-10 - measures energy released
62
positve of mms
- more accurate than richter scale - can describe very small earthquakes
63
positive + negative of Richter scale
- relatively easy to understand - cant give clear calculations to very powerful earthquakes
64
Mercalli scale
- scale between I - XII - measures impact/damage
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positve + negative of mercalli scale
- easy to understand - damage is subjective
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Primary impacts of earthquakes
ground shaking ground rupture - visible breaking of earths surface
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secondary impacts of earthquakes
- soil liquefaction - soils lose their mechanical strenth and behave like a fluid - landslides/avalanches - tsunamis - shallow focus under water - fires - broken gas pipes + electricity transmission systems -
68
Signs to predict an earthquake
- microquakes - decreasing radon gas concentrations in groundwater - raised groundwater levels - increased argon gas content in the soil - curious animal behaviour
69
earthquake resistant structures
- putting large weights on roof of building to counteractshockwaves - rubber shock absorbers in foundation - cross-bracing holds building together
70
nature of earthquakes are affected by...
- margin type - deestructive = higher magnitude - rate of plate movement - depth of focus - deeper focus = less damage. Howvever deeper focus = higher magnitude
71
distribution of tropical storms
- typhoons - south china sea + west Pacific ocean - hurricanes - gulf of mexico + Caribbean sea - cyclones - bay of Bengal, Indian ocean + northern australia
72
characteristics of tropical storms
- heavy rainfall - high wind speeds (119 kmph) - high waves + strom surges
73
factors affecting the formation of tropical storms
- oceans - gain large amounts of moisture from oceans, sea surface temperatures need to be over 27°C to provide energy - if wind shear too high, can disrupt the development - Coriolis effect - rotation of the Earth causes the air to move around the centre of the eye in a circular or rotating motion - between 5° and 20° north and south of the equator where ocean waters are warmest and the Coriolis effect is strongest
74
stages of tropical storm formation
- intense heating of sea surface causes warm, moist air to rise rapidly which cools and condenses forming cumulonimbus clouds - this creates areas of low pressure at the surface - surrounding air rushes in to replace it, creating strong surface winds sustaining storm - Coriolis effect causes system to start rotating
75
features of a tropical storm
centre = eye (very low pressure) eyewall - rising air spiracles around the eye - spin anticlockwise in northern hemisphere + clockwise in southern - lose strength over land due to no supply of warm, moist air - move westwards due to easterly winds
76
how are tropical storms measured
Saffir Simpson scale - rates storms from category of 1-5 (5 being the strongest) - measured wind speeds + damage
77
prediction of tropical storms
involves gathering data from stellites, weather balloons, radar the data includes atmospheric pressure, wind speed, humidity, sea surface temperatures + ocean currents
78
mitigation of tropical storms
- land use zoning can help reduce the impacts limiting development in high risk areas - building designs - on stilts to avoid flood waters, reinforced with concrete, fixed roofs rather than tiles - defences suh as sea walls to protect from storm surges - restroring natural ecosystems e.g magrove absorb energy of strom surges
79
what are ground fires
burn beneath the ground with tree roots + peat layers burning - slow, smouldering fire - no visible flame + little smoke - burn for days + weeks
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what are surface fires
burn through low lying vegetation + leaf litter - most common + can move quickly
81
what are crown fires
burn through the canopy layer - most dangerous + destructive - move quickly + produce intense heat + flames
82
how does vegetation type favour a wildfire
- denser vegetation - flammable types of vegetatio e.g eucalyptus + pine contain oils
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how do fuel characteristics favour wildfires
fine, dry material e.g grasses + twigs can burn very eaily
84
how does climate favour wildfires
- dry weather - dry out vegetation + increase flammability - high temps - increase evaporation drying out vegetation - strong winds provide more oxygen to help fire spread
85
what is El nino
a cyclical climatic condition that occurs every 6-8 years involving the warming of the Pacific ocean affecting global patterns of temperature + rainfall - causing warmer and drier conditions In Australia, Indonesia, ect...
86
how does slope angle affect wildfires
- steeper slope, more rapid fire burns due to rising of hot air - burn up hill in day + downhill at night
87
human causes of wildfires
- ciggarettes - campfires + BBQ - sparks from machinery
88
natural causes of wildfires
- lightning strikes - volcanic eruptions - heat from sun
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