Natural Hazards Flashcards
(125 cards)
1
Q
What is a hazard?
A
A potential threat to human life and property caused by an event.
2
Q
Would a hurricane hitting an uninhabited desert island be a hazard?
A
No, as no people/property is affected.
3
Q
What is a natural disaster?
A
When a natural hazard comes into contact with a vulnerable population.
4
Q
What is the name of the model that shows the difference between hazards and disasters?
A
Degg’s model.
5
Q
What are the three major types of geographical hazards?
A
Geophysical, atmospheric and hydrological.
6
Q
What is a geophysical hazard?
A
A hazard caused by land processes. This is usually in the form of tectonic plates.
7
Q
What is an atmospheric hazard?
A
A hazard that is caused by atmospheric processes and the conditions created because of these processes.
8
Q
What is a hydrological hazard?
A
Hazards caused by water bodies and movement.
9
Q
Give an example of each type of hazard.
A
Geophysical: Earthquake, Tsunami, Volcano, Landslide.
Atmospheric: Wildfires, Tropical Storms.
Hydrological: Flooding.
10
Q
How does a person’s perception of a hazard affect vulnerability?
A
If people believe there is no chance of a hazard occurring, then they are unlikely to attempt to mitigate a hazard. However, if they fear the hazard occurring they will try and mitigate its effects.
11
Q
What are the three main ways humans respond to hazards?
A
Fatalism, Domination and Adaptation.
12
Q
What is fatalism?
A
The viewpoint that hazards are uncontrollable natural events and any losses should be accepted as there is nothing that can be done to stop them.
For example, they would accept that their community will flood during the monsoon season.
13
Q
What is domination?
A
The viewpoint that science and technological advancements will have the ability to lessen the impacts of a natural hazard.
For example, they would build flood defences in places that flood during the monsoon season.
14
Q
What is adaptation?
A
The viewpoint that people can live with the threat of hazards by adapting their way of life.
These people would build their houses on stilts so that the floods do not affect them as much.
15
Q
What is the frequency of a hazard?
A
How often a hazard occurs.
For example, every year or once every 100 years.
16
Q
What is the distribution of a hazard?
A
Where a hazard appears geographically.
For example, there is a high distribution of volcanoes around the Pacific Ring of Fire.
17
Q
What is the magnitude of a hazard?
A
The size of the hazard.
18
Q
What is the intensity of a hazard?
A
The amount of damage a hazard causes.
19
Q
What is the difference between the magnitude and intensity of a hazard?
A
The magnitude is how large a hazard is and doesn’t change based on location. The intensity is the effect it has on the community.
For example, a 7.0 magnitude earthquake would have a different intensity if it hit a sparsely populated area in the USA compared to a densely populated area in India.
20
Q
How does a country’s level of development affect the intensity of a hazard?
A
HICs can usually afford more mitigation strategies and therefore have less severe effects of a hazard.
21
Q
What are the two models that show how humans respond to hazards?
A
The Park Model and the Hazard Management Cycle.
22
Q
What does the Park Model show?
A
It shows how a hazard affects the quality of life in an area. It then shows the rough timescale of how the quality of life rebounds in the days/weeks/years after a hazard.
23
Q
What does the steepness of the curve on the Park Model show?
A
It shows how quickly the quality of life in an area deteriorates and recovers after a disaster.
24
Q
What does the depth of the curve show in the Park Model?
A
The scale of the disaster and how much a hazard impacts the quality of life.
The deeper the curve, the greater the drop in quality of life.
25
What is the main advantage of the Park Model?
It allows hazards to be compared to each other.
26
What are the four stages of the Hazard Management Cycle?
Preparedness, Response, Recovery, Mitigation.
27
What is preparedness in the HMC?
Being ready for an event to occur.
For example, public awareness, education and training.
28
What is response in the HMC?
Immediate action taken after an event.
For example, evacuation, medical assistance, rescue.
29
What is recovery in the HMC?
Long term responses after a hazard.
For example, restoring services and reconstruction.
30
What is mitigation in the HMC?
Strategies to lessen the effects of another hazard.
For example, flood defences, warning signals developed.
31
What are the six layers of the Earth?
Inner core, outer core, mantle, asthenosphere, lithosphere, crust.
32
What is the structure of the inner core?
A solid ball of iron and nickel. It is very hot due to radioactive decay and it is responsible for the Earth's internal energy.
33
What is the structure of the outer core?
Semi molten and made of nickel and iron.
34
What is the structure of the mantle?
Mainly solid rocks with a high silicon content. However, the top layer of the mantle is semi-molten. This is the asthenosphere.
35
What is the structure of the asthenosphere?
A semi-molten layer that constantly moves due to flows of heat in convection currents.
36
What is the structure of the lithosphere?
The lithosphere is broken up into plates. The majority of the lithosphere is within the mantle but the lithosphere includes the crust and tectonic plates.
37
What is the structure of the crust?
The thin top layer of the lithosphere. Contains two types of solid crust, continental and oceanic.
38
What is the difference between oceanic crust and continental crust?
Oceanic crust is thinner.
Oceanic crust is denser.
Oceanic crust is younger as it can be destroyed and reformed by plate movement.
39
What is the general consensus for the reason why tectonic plates move?
Convection currents in the asthenosphere pushing the plates around.
40
What are the three types of tectonic plate boundary?
Conservative, Constructive and Destructive.
41
How do the plates move at a destructive plate boundary?
Tectonic plates move towards each other.
42
How do the plates move at a constructive plate boundary?
The plates move away from each other.
43
How do the plates move at a conservative plate boundary?
The move parallel to each other.
44
What tectonic hazards are found at destructive plate boundaries?
Volcanoes and earthquakes.
45
What tectonic hazards are found at constructive plate boundaries?
Volcanoes and earthquakes.
46
What tectonic hazards are found at conservative plate boundaries?
Earthquakes but not volcanoes.
47
What landforms are there at destructive plate boundaries?
Fold mountains, island arcs and deep sea trenches.
48
What landforms are there at constructive plate boundaries?
Ocean ridges and rift valleys.
49
How does a volcano form at a destructive plate boundary?
1) The oceanic plate subducts underneath the continental plate due to its higher density.
2) The oceanic crust is melted as it subducts into the asthenosphere.
3) The extra magma created causes pressure to build up.
4) Pressurised magma forces its way through weak areas in the continental crust.
5) Explosive, high pressure volcanoes erupt through the continental plate.
50
How does a volcano form at constructive plate boundaries?
1) As the plates are moving apart, magma rises in the gap left between the plates.
2) Less explosive volcanoes occur due to the lack of pressure.
51
What is seafloor spreading?
Two tectonic plates moving away from each other which causes magma to rise up between the gap.
52
What is the main evidence for sea floor spreading?
Paleomagnetism.
53
What is paleomagnetism?
1) When magma rises to fill the gap between two plates at a constructive boundary, the iron particles align to the Earth's magnetic field.
2) However, when the magma solidifies, the iron particles are stuck in the orientation they were before.
3) As the Earth's magnetic field switches, the direction of the iron particles changes.
4) This leaves symmetrical bands of rocks with alternating bands of magnetic polarity.
54
What are two other theories for continental drift?
Ridge Push / Gravitational Sliding
Slab Pull
55
What is ridge push / gravitational sliding?
The gradient created when plates move apart act under gravity as they have a higher elevation. Gravity causes the plates to move further away from each other.
56
What is slab pull?
When an oceanic plate subducts, the plate sinking into the mantle pulls the rest of the plate with it causing further subduction.
57
What is a hotspot?
An area of volcanic activity that is not related to plate boundaries.
58
How are volcanoes formed at hotspots?
At a weakness in the crust or exceptionally hot magma, the magma can push through the crust forming a volcano that is not related to plate boundaries.
59
How are island arcs formed?
The hotspot plume stays in the same place but the plates continue to move which causes a chain of islands.
For example, Hawaii.
60
What are the two types of lava?
Andesitic and Basaltic.
61
What are the features of andesitic lava?
It has a high silica content.
It has a high viscosity (it is thick).
62
What are the features of basaltic lava?
It has a low silica content.
It has a low viscosity (it is runny).
63
What are the features of a composite volcano?
It has steep sides.
It has alternating layers of solidified lava and ash.
Violent eruptions.
64
What type of lava are composite volcanoes caused by?
Andesitic lava.
65
What are the features of a shield volcano?
Gently sloping sides.
No layers.
Less violent eruptions.
66
What type of lava causes shield volcanoes to form?
Basaltic lava.
67
What is a lava flow?
When lava flows above the ground and can set fire to trees and buildings.
68
What is a lahar?
When rainfall or melting ice causes ash and mud from a recently erupted volcano to slide down the volcano at very high speeds.
69
What is a jökulhlaup?
When high temperatures from magma melt glaciers or ice sheets quickly which causes flooding.
70
What is tephra?
Any type of rock that is ejected by a volcano.
71
How do toxic gases pose a threat?
They are emitted in high quantities during an eruption and can cause respiratory problems and acid rain.
72
How is acid rain caused?
When gases such as sulphur dioxide mix with water, sulphuric acid is formed.
73
What is a pyroclastic flow?
Clouds of burning hot ash and gas that collapses down a volcano at incredibly high speeds (up to 430 mph).
74
How is the strength of volcanoes measured?
Using the Volcanic Explosivity Index (VEI).
75
How can preparedness occur for a volcanic eruption?
Authorities can install monitoring systems to predict when an earthquake could happen and plan for what to do when there is an eruption.
Individuals can make sure they are prepared by making emergency supply kits.
76
How can adaptation occur for a volcanic eruption?
Buildings can be strengthened to reduce the chance of collapse if ash lands on them.
People can capitalise on the opportunities of living near a volcano.
77
What causes earthquakes?
Friction between two tectonic plates. The pressure builds up until it cannot hold and the plates move suddenly past each other.
78
Where is the focus of an earthquake?
The point underground where the earthquake originated from.
79
Where is the epicentre of an earthquake?
The point above ground directly above the focus.
80
How is the strength of an earthquake measured?
Using the Richter scale.
The Modified Mercalli Scale can also be used.
81
What is the main feature of the Richter Scale?
It is logarithmic (an increase of 1 in the scale represents a 10 times increase in energy).
82
How is the Modified Mercalli Scale used?
It gives a value between 1 and 12 in roman numerals.
It uses visual indicators to measure the strength of the earthquake.
83
What three hazards can be caused by earthquakes?
Tsunamis
Landslides/Avalanches
Soil Liquefaction
84
What is a tsunami?
Large waves triggered by the displacement of large volumes of water.
85
How are tsunamis formed?
1) Earthquakes cause the seabed to move which displaces water.
2) Waves radiate out from the epicentre of the earthquake.
3) The waves travel very fast in deep water and increase in height close to land as the seabed becomes shallower.
86
How does a landslide occur?
Shaking of the ground can dislodge rocks, soil or snow which causes landslides that move downslope very quickly.
87
What is soil liquefaction?
When soil is saturated with water, the vibrations of an earthquake can cause it to act like a liquid.
88
How does the plate margin type affect the magnitude of an earthquake?
Greater pressure at destructive plate boundaries cause higher magnitude earthquakes.
Earthquakes at constructive margins tend to be lower magnitude.
89
What are the frequency of earthquakes?
Low magnitude earthquakes happen very regularly.
High magnitude earthquakes occur much less often.
90
What is the regularity of earthquakes?
Earthquakes are not regular - they are very random.
91
How predictable are earthquakes?
Scientists are able to predict areas that are likely to have earthquakes (along plate margins).
However, they are unable to predict when an earthquake will strike and its magnitude.
92
How can preparedness occur for an earthquake?
Authorities can install earthquake warning systems and warnings can be sent out by text.
Authorities and individuals can be trained on how to react to an earthquake.
93
How can adaptation occur for an earthquake?
Buildings can be designed to withstand earthquakes.
Buildings can also be designed to reduce the vulnerability to tsunamis.
94
What is a tropical storm?
A huge spinning storm with strong winds and torrential rain.
95
How do storms develop?
As warm, moist air rises and condenses, energy is released that increases the wind speed.
96
What conditions are required for a storm to form?
Sea water above 27 degrees to at least 50 metres deep.
A location at least 5 degrees from the equator which allows the Coriolis effect to be strong enough.
97
What do tropical storms look like?
They are circular in shape and can be hundreds of kilometres wide.
At the centre, there is an area of very low pressure called the eye.
Rising air spirals around the eye in the eyewall, causing very strong winds.
Near the top of the storm there is an outflow of moisture laden air.
98
What scale measures the magnitude of storms?
The Saffir-Simpson Scale
99
Are storms predictable?
Satellite imagery can be used to track potential storms over the ocean and therefore a few days of warning can be provided before a storm hits land.
100
What are some hazards from storms?
High winds
Storm surge
Heavy rain
Flooding
Landslides
101
How do high winds cause a hazard?
Winds can destroy buildings, uproot trees and carry debris for long distances before smashing them into other objects.
102
What is a storm surge?
A large rise in sea level caused by high winds pushing water towards the coast and by the low pressure of a storm.
103
How is flooding caused after a storm?
Heavy downpours cause river discharge to increase suddenly and the river bursts its banks.
Storm surges can also cause flooding.
104
How can storms cause landslides?
Water infiltrates soil and rock making it heavier and therefore less stable.
105
How can preparedness occur for a tropical storm?
Emergency services can be trained and evacuation routes can be made.
106
How can adaptation occur for storms?
Buildings can be designed to withstand storms and storm surges.
Flood defences can be built along the coast and rivers to prevent storm surges.
107
What is a wildfire?
An uncontrolled fire that destroys forests, grasslands and other areas of vegetation.
108
What are the three types of wildfire?
Ground fire
Surface fire
Crown fire
109
What is a ground fire?
Where the ground itself (roots and peat) burns.
110
What are the characteristics of a ground fire?
Slow moving, smouldering fire with no flame and little smoke.
111
What is a surface fire?
Where leaf litter and low-lying vegetation burns.
112
What are the characteristics of surface fire?
They can be high or low intensity depending on the availability of surface vegetation.
113
What is a crown fire?
Where fire moves rapidly through the canopy (the top layer of vegetation).
114
What are the characteristics of a crown fire?
Fires are intense and fast-moving.
115
What are four conditions that affect the intensity of wildfires?
Vegetation type
Fuel characteristics
Climate and recent weather
Fire behaviour.
116
How does vegetation type affect the intensity of a wildfire?
Thick undergrowth and closely spaced trees allow a fire to spread easily.
Some trees, such as eucalyptus and pine contain oil which burns very easily.
117
How do fuel characteristics affect the intensity of a wildfire?
Fine, dry materials catch fire and burn most easily.
Large amounts of fuel that form a continuous cover will make the fire burn for longer and spread quicker.
118
How does climate and recent weather affect the intensity of wildfires?
Wildfires are more likely during periods of drought where fuel is dry and flammable.
Strong winds provide more oxygen to encourage the fire to burn and spread.
119
How does fire behaviour affect the intensity of the wildfire?
Ground fires travel slowly whereas crown fires travel much quicker.
120
What are natural causes for wildfires?
Lightning
Volcanic eruptions
121
What are the human causes for wildfires?
Cigarettes
Campfires / BBQs
122
What are short term responses to wildfires?
Trying to put the fire out.
Evacuating people.
Spraying water onto the roofs of houses to prevent them from igniting.
123
How can prevention occur for a wildfire?
People can be educated about the risks of using campfires in vulnerable areas.
124
How can preparedness occur for a wildfire?
Emergency plans and supplies can be created in case of a wildfire.
125
How can adaptation occur for a wildfire?
Buildings can be built out of non-flammable materials.
Fire breaks can be created to stop fires from spreading.
