AQA A Level Geography- Hazards

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What is a hazard?

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243 Terms

1

What is a hazard?

A potential threat to both people and property.

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2

What is the difference between a hazard and a disaster?

A disaster occurs when a vulnerable population is exposed to a hazard.

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3

What are geophysical hazards?

Hazards caused by land processes- earthquakes, tsunamis, volcanic eruptions.

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4

What are atmospheric hazards?

Hazards caused by atmospheric processes and the conditions created because of these, such wildfires.

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5

What are hydrological hazards?

Hazards caused by water bodies and movement e.g. floods.

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6

How does wealth affect hazard perception?

May see hazards as smaller threats, as they can move to areas that are less at risk or build homes to withstand hazards. May see them as greater economic loss.

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7

How does religion affect hazard perception?

Some may view hazards as put there by God for a reason, or being part of the natural cycle of life, so may not perceive them to be negative.

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8

How does level of education affect hazard perception?

Those more educated about hazards may understand their full effects and how devastating they can be. Those who are less educated may not understand the full extent of a hazard and may not evacuate etc.

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9

How does experience affect hazard perception?

Someone who has experienced more hazards may be more likely to understand the full effects. Studies suggest that people who have experienced hazards are likely to have an optimistic outlook on future hazards.

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10

What is fatalism?

A passive hazard response; the view that hazards are uncontrollable events, and any losses should be accepted as there is nothing that can be done to stop them.

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11

What is adaptation?

Attempting to live with hazards by adjusting lifestyle choices so that vulnerability to the hazard is lessened.

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12

What is mitigation?

Strategies carried out to lessen the severity of a hazard.

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13

What is hazard management?

Coordinated strategies to reduce a hazard’s effects. This includes prediction, adaptation, mitigation.

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14

What is risk sharing?

A form of community preparedness, where the community shares the risk posed by a natural hazard and invests collectively to mitigate the impacts of future hazards.

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15

How does the incidence of a hazard affect human responses?

Low incidence hazards may be harder to predict and have less management strategies put in place, meaning the hazard could be more catastrophic when it does eventually occur.

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16

How does the distribution of a hazard affect human responses?

Areas of high hazard distribution are likely to have lots of management strategies, and will be adapted to the hazardous landscape as it dominates the area.

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17

How does the magnitude of a hazard affect human responses?

High magnitude hazards will have worse effects, meaning they will require more management to lessen the effects and ensure a relatively normal life can be carried out after the hazard.

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18

How does level of development affect human responses to hazards?

An area with a lower level of development is less likely to have effective mitigation strategies as these are costly- effects are more likely to be catastrophic.

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19

Why do people put themselves at risk of a hazard?

Hazards are unpredictable; lack of alternatives; Hazard perception.

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20

Define community resilience.

The ability of a community to utilise resources to respond to, withstand and recover from natural disasters.

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21

Define hazard prediction.

Early warning systems to help monitor a hazard.

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22

What is the park model?

A graphical representation of human responses to hazards. Shows the steps carried out in the recovery after a hazard and a rough time frame, can be used to compare hazards.

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23

What does the gradient of the line show on the park model?

How quickly an area deteriorates and recovers.

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24

What does the depth of the line show on the park model?

The scale of the hazard.

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25

What happens during the relief stage of park model recovery?

Immediate local response e.g. medical aid, search and rescue. Immediate appeal for foreign aid- global response.

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26

What happens during the rehabilitation stage of park model recovery?

Services begin to be restored, temporary shelters and hospitals set up, food and water distributed, coordinated foreign aid.

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27

What happens during the reconstruction stage of park model recovery?

Infrastructure rebuilt, quality of life improves or returns to normal, mitigation efforts put in place for future events.

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28

What are the disaster management cycle stages?

Preparedness, response, recovery, prevention/mitigation.

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29

What is preparedness in the hazard management cycle?

Being ready for an event to occur e.g. public awareness, education, training.

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30

What is response in the hazard management cycle?

Immediate action taken after event e.g. evacuation, medical assistance, rescue.

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31

What is recovery in the hazard management cycle?

Long-term responses e.g. restoring services, reconstruction.

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32

What is prevention/mitigation in the hazard management cycle?

Strategies to lessen effects of another hazard e.g. barriers, warning signals.

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33

What is distribution?

The spatial coverage of the hazard. Some hazards have localised or wider effects.

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34

What is magnitude?

The strength of the hazard.

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35

What is frequency?

The distribution of hazards through time.

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36

What are the contents of the inner core?

Solid iron/nickel. Very hot due to radioactive decay. Heat is responsible for earth’s internal energy.

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37

What are the contents of the outer core?

Semi-molten iron and nickel.

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38

What are the contents of the mantle?

Mainly solid rock, high silicon content.

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39

What is the asthenosphere?

Semi-molten layer containing upper mantle, constantly moves due to convection currents powered by heat from core. Below the lithosphere.

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40

What is the lithosphere?

The top of the lithosphere is the crust, which is broken up into plates.

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41

Characteristics of continental crust:

Thicker (30-70km), less dense, older.

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42

Characteristics of oceanic crust:

Thinner (6-10km), more dense, younger.

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43

What is plate tectonic theory?

The lithosphere is broken up into tectonic plates, that move in relation to each other. The areas where these meet are called plate boundaries.

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44

What are convection currents?

Lower parts of the asthenosphere heat up as they are close to the core, become less dense, and rise. They cool down at the top of the asthenosphere, become more dense, and sink.

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45

What is slab pull?

A heavier, denser, oceanic plate subducts under the lighter, less dense continental plate. As the plate sinks, gravity pulls the plate down into the mantle.

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46

When is a subduction zone formed?

When two plates move towards each other.

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47

What is ridge push/gravitational sliding?

As the crust moves away from a mid-ocean ridge, it cools and becomes denser. Crust slopes away from the ridge and gravity pulls crust down, pushing it forwards. Puts pressure on plates, causing them to move.

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48

How does seafloor spreading occur?

Plates diverge, magma rises up to fill the gap, and cools to form crust. New crust is pulled apart and more crust forms. Under the sea, the sea floor gets wider, creates mid-ocean ridges.

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49

What happens at a constructive plate boundary?

Plates diverge, both volcanic eruptions and earthquakes can occur, creates ocean ridges and rift valleys.

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50

How are volcanoes formed at constructive plate boundaries?

Pressure in mantle is released as plates move apart, causing mantle to melt, producing magma. Magma is less dense than the plate above, so can rise and erupt.

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51

How are ocean ridges formed?

Plates move apart and seafloor gets wider.

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52

How are rift valleys formed?

Plates diverge, rising magma causes crust to form fault lines. As the plates move further apart, the crust between parallel fault lines drops to form a valley.

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53

What happens when two oceanic plates meet at destructive plate margins?

Plates move towards each other. The denser of the two is subducted, which can create deep sea trenches, earthquakes, volcanic eruptions, and island arcs.

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54

How are deep sea trenches formed?

Where continental and oceanic plates meet at a destructive plate boundary, the oceanic plate is subducted, forming a trench.

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55

How are fold mountains formed?

Both plates are of similar densities and are less dense than oceanic plates, so pressure builds. Continental crust piles up on top of the lithosphere due to pressure.

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56

How are composite volcanoes formed?

Denser oceanic plate is subducted at a destructive plate boundary. Oceanic crust is melted as it subducts into the asthenosphere, magma produced increases pressure. This forces through the weak continental plate, causing volcanic eruption.

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57

How are island arcs formed?

Two oceanic plates meet at a destructive plate boundary. The denser plate is subducted, pushing sediment upwards and creating magma as the other plate melts. This magma erupts through the crust, and cools underwater, forming curved chains of islands.

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58

What occurs at conservative plate margins?

Two parallel plates move at different directions or different speeds. This causes pressure to build up, which can create earthquakes.

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59

Why is there no volcanic activity at destructive plate margins where 2 continental plates meet, and at conservative plate margins?

No plates are subducted, so no magma is produced that can erupt.

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60

What is a hotspot?

Areas of volcanic activity that are not related to plate boundaries.

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61

How do hotspots create volcanoes?

Hot magma plumes from the mantle rise and burn through weaker areas of crust. This creates a chain of islands as the plates move, but the hotspot is stationary. The islands then erode and subside.

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62

What are the characteristics of shield volcanoes?

Basaltic, runny, hotter lava, frequent eruptions, not very violent.

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63

What are the characteristics of composite volcanoes?

Andesitic, rhyolitic, cooler lava, more viscous, violent, intermittent eruptions.

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64

What are the primary hazards of volcanoes?

Nuees ardentes, lava flows, gases, tephra, pyroclastic and ash fallout.

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65

What are the secondary hazards of volcanoes?

Mudflows, acid rain.

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66

What are nuees ardentes?

A mixture of heated gas, ash, and volcanic rock that flows down the side of a volcano. Travels at around 80km/h. Can cause widespread death and destruction, e.g. due to burning.

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67

What are lava flows?

Movement of lava down the sides of a volcano. The speed and distance travelled depends on temperature, viscosity, and topography. Can flow up to 10km/h.

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68

How do lava flows present as a threat?

They destroy anything in their path, by burning or knocking them down. However most flows are relatively slow, so people have time to evacuate.

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69

What are volcanic gases?

Lava releases carbon dioxide and sulphur dioxide when volcanoes erupt. Can cause harm to animals e.g. breathing difficulty.

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70

What is pyroclastic fallout/tephra?

Solid material of varying sizes that is ejected by a volcano – ranges from ash (less than 2mm) to volcanic bombs (more than 64mm)

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71

How does tephra present as a threat?

Large pieces can damage buildings, and kill or injure people.

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72

What is ash fallout?

Large quantities of ash carried by the wind and deposited on the ground. can travel many km, causing respiratory problems, injuries, damage, deaths and disruption to transport

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73

What are mudflows/lahars?

Occur when volcanic material mixes with large quantities of water, e.g. from rainfall. Flows move quickly and can travel for kilometres. Can bury or destroy habitats and settlements.

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74

What is acid rain?

When volcanic gases react with water vapour, producing sulfuric acid and carbonic acid that falls as rain. Can damage ecosystems and cause rocks to deteriorate.

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75

How does the magnitude of volcanoes vary?

Can range from small events to large eruptions of lava, gas, and ash. Measure using Volcanic Explosivity Index, a logarithmic scale from 0-8.

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76

How does the frequency of volcanoes vary?

Some erupt every 100,000 years, others erupt every few months. Less frequent eruptions are typically larger in magnitude.

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77

What is the spatial distribution of volcanoes?

Located along constructive or destructive plate boundaries, and hotspots. Ring of fire- area of high volcanic activity in the pacific ocean.

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78

How are volcanic eruptions regular?

Eruptions in each type of boundary are typically similar.

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79

How can volcanic hazards be predicted?

Regularity of eruptions can help estimate when eruptions will take place. Seismic activity, gases releasing, can all indicate an eruption, but there is no definite predictions to a volcanic eruption.

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80

How are seismic waves/shockwaves formed?

Friction between plates causes currents in the asthenosphere to push, building up pressure. When this pressure is released, seismic movement spreads throughout the ground.

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81

What is the focus?

The point underground where the earthquake originates from.

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82

What is the epicentre?

The area above ground that is directly above the focus.

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83

What are earthquakes?

Shockwaves spread out from the focus, caused by tension at the plate boundary. Causes the ground to shake and rupture.

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84

What is a tsunami?

Large waves caused by the displacement of large volumes of water.

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85

How are tsunamis formed?

Underwater earthquakes cause the seabed to move, waves radiate from the epicentre. Water is displaced, creating a wave that moves towards land.

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86

How are landslides formed?

Shaking of the ground can dislodge rocks or soil. Can also loosen material so more water infiltrates, and the weight of this can cause a landslide after the ground has stopped shaking.

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87

What is soil liquefaction?

When soil is saturated, the vibrations of an earthquake cause it to act like a liquid. Soil becomes weaker and more likely to subside when it has large weight on it.

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88

Spatial distribution of earthquakes:

Along all plate boundaries- ring of fire accounts for 90% of all earthquakes.

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89

What is the Richter scale?

Measures the strength of seismic waves, logarithmic scale from 1-10.

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90

What is the moment magnitude scale?

Based on the total amount of energy released from an earthquake. Is logarithmic and has no upper limit, more accurate than Richter scale.

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91

What is the Mercalli scale?

Measures the impacts of an earthquake using observations of the event. From 1-12, in roman numerals.

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92

What factors affect the magnitude of earthquakes?

Margin type, depth of focus, rate of movement.

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93

What is the general frequency of earthquakes?

Low magnitude earthquakes occur around the world at plate boundaries daily, whereas stronger earthquakes are less frequent.

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94

How can earthquakes be predicted?

Are almost impossible to predict. Microquakes may give some indication but the magnitude cannot be predicted as how strong they are is random.

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95

How can we build earthquake-proof buildings?

Cross bracing, concrete counterweight, rubber shock absorbers.

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96

What is a tropical storm?

A low pressure, spinning storm with high winds and torrential rain.

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97

How warm does the ocean need to be to create a tropical storm?

27 degrees and at least 50 metres deep. Warm water provides the storm with energy.

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98

What latitudes can tropical storms form at?

Between 5 and 30 degrees n/s of the equator, due to the strong Coriolis effect.

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99

What does air pressure need to be to form tropical storms?

Unstable- usually where high pressure and low pressure meet, so that warm, moist air rises more readily and clouds can form.

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100

What does wind shear need to be like for tropical storms to form?

Winds must be present for the swirling motion to form, but not too strong or the storm system will be ripped apart in the early stages.

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