Hazards Flashcards
(150 cards)
1
Q
What is a natural hazard?
A
events that are perceived to be a threat to people, the built environment and the natural environment.
2
Q
Explain the difference between a hazard and a disaster:
A
A disaster is the result of a hazard. A hazard is the potential threat. Living at the bottom of a mountain is a hazard, an avalanche/rockslide is a disaster.
3
Q
Features that help define events as natural hazards:
A
-distinct effects
-little or no warning
-involuntary exposure
-damage takes place shortly after hazard
-impacts may be long term e.g. disease, disrupted economy.
-scale and impact requires emergency response.
4
Q
Define perception
A
The way that people view the threat of a hazard event. This will determine the course of action or response.
5
Q
Factors that influence perception:
A
-Socio-economic status
-level of education
-employment status
-religion/culture
-family/marital status
-past experience
-values/personality
6
Q
Define fatalism (Perception)
A
A view of a hazard that suggests people can’t influence or shape the outcome, therefore nothing can be done about it. e.g. religious views - god’s will.
7
Q
Define adaptation (Perception)
A
For places which experience regular hazards a response is often to adapt or adjust their behaviour to be able to cope with future events better.
It is more likely for developed counties to adapt due to the cost needed to provide the relevant adaptation strategies. e.g., homes in ‘tornado alley’ (USA) often have tornado shelters dug into the ground into which a family can be evacuated.
8
Q
Define fear (Perception)
A
Perception of a hazard in which people feel so vulnerable that they can’t face living there and will move away.
9
Q
How are Hurricanes measured?
A
Saffir-Simpson hurricane wind scale
10
Q
How are earthquakes measured?
A
Richter scale
11
Q
How are wildfires measured?
A
Flame characteristics and rate that energy is released
12
Q
Reasons people may put themselves at risk of a natural hazard:
A
-hazards are unpredictable
-Lack of alternatives
-Changing level of risk - overtime places that were once safe are now dangerous.
-Cost/benefit
-Perception
13
Q
What is the equation to measure risk?
A
(Frequency/magnitude of hazard x vulnerability) /divided by/ capacity to cope or adapt.
14
Q
Where can responses to natural hazards come from? (List)
A
-individuals
-local community working together
-national government
-international agencies
15
Q
Define community resilience
A
the sustained ability of a community to utilise available resources to respond to, withstand and recover from the effects of natural hazard events.
16
Q
Describe prediction
A
Give warnings where possible, improved monitoring.
17
Q
The issue with prevention:
A
very difficult and unrealistic
18
Q
Define protection
A
Protecting people, possessions, built environment by modifying the environment. Also educate people, evacuation programmes.
19
Q
Define integrated risk management
A
The process of considering the social, economic and political factors involved in risk analysis and deciding on actions that need to be taken.
20
Q
Factors that hazard response depends on:
A
-Priorities e.g. jobs, health
-Past experience
-Economic wealth
-Technology and resources
-Quality of research and knowledge
-Attitudes and perceptions of decision makers
-Society and culture
21
Q
What does the park model show?
A
The strategies and approaches taken to being ‘back to normal’ after a disaster. The curve demonstrates the scale of the disaster.
22
Q
Give examples of relief
A
Search, rescue, care operations take place. Medical supplies, rescue equipment, expertise, clothing and food may be flown in. Potentially local and global response.
23
Q
Describe rehabilitation
A
Can last weeks or months. Restore physical and community infrastructure/services. More complex, requires assessment of needs and coordinated planning of resources.
24
Q
Describe reconstruction
A
Permanent changes are introduced, which are the same or better QOL and economic stability than before.
25
Give criticisms of the park model
-Doesn't take into account spatial variation meaning that it assumes that all area of a country recover at the same rate.
-Can't be effectively used for more than one event as multiple park model curves may be time consuming and confusing.
-Although its good to visually compare its not good at showing quantitative data, this makes the comparison problematic as it doesn't show number of deaths, homes destroyed etc.
26
List mitigation strategies
-Building structures that withstand hazards
-Stockpiling food and drink
-Preparing evacuation routes
-Text alerts
-Satellite tracking
-Training emergency services
-Lab simulation of impacts
27
Negative implications of mitigating 'super catastrophes':
-Perceptions will be that everything is being dealt with so less people will evacuate - death toll could be high.
-Finding investment for mitigation procedures may deny money to other pressing causes.
28
Positive implications of mitigating 'super catastrophes':
-Reduced death toll
-Reduced impact on infrastructure
-Reduced cost for long term response
29
What is the thickness of the mantle?
2900km
30
Describe the inner core
-Solid
-iron-nickel alloy
-Can reach 5000 degrees C
31
Describe the outer core
-Semi-liquid
-Mainly iron
-Can reach 5000 degrees C
32
What elements is the oceanic crust made of?
Silica and magnesium (SIMA)
33
What is the thickness of the oceanic crust?
5-10km (denser)
34
How old is the oceanic crust?
less than 200 mill yrs old (young)
35
What elements is the continental crust made of?
Silica and aluminium (SIAL)
36
What is the thickness of the continental crust?
20-70km
37
How old is the continental crust?
3.8 billion yrs old (older)
38
What is the Asthenosphere?
Lies beneath the lithosphere, is semi-molten on which plates float and meet.
39
What is Rheid?
A non-molten solid that deforms by viscous or plastic flow, in response to an applied force.
40
What is continental drift?
The theory that the continental landmasses have changed position over time, created by Alfred Wegener (1912).
41
What are the names of the 2 continents Pangea became?
Laurasia and Gondwanaland
42
Give two pieces of geological evidence for the theory of plate tectonics:
-Rocks the same age and type with the same formations have been found in SE Brazil and S Africa.
-The west of Africa seems to fit together with the east of South America, especially when the continental shelves are examined.
43
Give two pieces of biological evidence for the theory of plate tectonics:
-Plant remains from humid swamps have been found only in India and Antarctica.
-Fossil remains of a mesosaurus have been found in South America and Africa, its unlikely that they could have developed in the same way or migrated across the Atlantic.
44
Give two pieces of climatological evidence for the theory of plate tectonics:
-Similar glacial deposits have been found in Antarctica, S America and India.
-Coal deposits of a similar age, formed in tropical conditions have been found in Antarctica, the UK, and N America, none of which are located in tropical areas.
45
What is sea floor spreading?
Hess gathered evidence that new sea floor was being created at a rate of 5cm per year. The oldest rocks on the edge and the newest still being formed in the centre. This refines Wegener's theory and also explains why continental plates are older than oceanic.
46
What led to the theory of subduction?
Discovery of the ocean trenches and that there is no sign of the earth growing but new crust is being formed all the time.
47
How quickly do tectonic plates move per year?
2cm-16cm
48
Explain the process of paleomagnetism:
1) When the lava erupts on the ocean floor, magma with iron rich particles align themselves with the magnetic fields of the earth.
2)Every 400,000 years the earth's polarity reverses and so the plates move to align themselves with the other pole.
3)The rocks are mirrored on either side of the mid Atlantic ridge. The result is a series of magnetic strips with alternatively aligned polarity with the others.
4)This enables us to date the rocks and understand that sea floor spreading takes place over a period of time.
49
What is magma?
Molten rock that is found beneath the surface of the earth.
50
What is igneous rock?
Rock that is formed when magma cools.
51
What is intrusive magma?
Magma deep in the earth
52
What is extrusive magma?
Magma above the earth's surface
53
What is ridge-push?
Gravity acting on the weight of the lithosphere pushes the older part of the plate away from the ridge.
54
What is slab-pull?
At destructive margins gravity forces lithosphere to descend into the mantle. The collision with the other plate causes both shallow and deep seismic activity.
55
What are hotspots?
Areas where great heat produces a persistent source of magma by partly melting the plate. The magma then rises through the mantle and crust to erupt onto the seafloor, forming an active seamount. Over time countless eruptions cause the seamount to grow until it finally emerges above sea level to form an island volcano.
56
How is a chain of islands created over a hotspot? e.g. Hawaii
They are created because the plate moves continuously, and eventually carries the island beyond the hotspot and volcanism ceases. As one becomes extinct, another one develops.
57
What is a mantle plume?
An upwelling of abnormally hot rock within the earth's mantle, thought to be the cause of hotspots.
58
What is a volcano?
A vent (opening) in the earths crust through which lava, tephra and gases erupt.
59
What is Tephra?
Ash, dust, fragments of material produced in a volcanic eruption.
60
What is an active volcano?
Active volcanoes have erupted in living memory.
61
What are dormant volcanoes?
Dormant volcanoes have erupted within historical record.
62
What are extinct volcanoes?
Extinct volcanoes won't erupt again.
63
What is an effusive eruption?
Occurs when hot, (1200 degrees) basaltic magmas reach the surface. Dissolved gases escape easily as the magma erupts, forming lava that flows downhill easily. (Less explosive) This occurs at shield volcanoes.
64
What is an explosive eruption?
Occurs when cooler, more viscous magma reaches the surface. Dissolved gases can't escape as easily, so pressure may build until gas explosions blast rock and lava fragments into the air. This occurs at Strata volcanoes (Composite).
65
Why are eruptions of basaltic lava not as explosive?
-Low in silica = more fluid
-Allows gas bubbles to expand on the way to surface - prevents explosive activity.
-Originate from upward movement of mantle = constructive margins.
66
Why are eruptions of Andesitic and rhyolitic lavas more explosive?
-High in Silica = very viscous.
-Often solidifies before reaching surface = pressure builds = violent explosion.
-Destructive margins
67
What is the VEI?
Volcano explosivity Index - used to measure the magnitude of volcanoes.
68
How does the VEI measure volcano magnitude?
Index goes from 1-8, and measures magnitude based on plume height and eruptive volume.
69
What is an example of a volcano that was believed to be extinct but erupted again?
Mt Vesuvius erupted in 79 AD - then again in 1944
70
Give and explain examples of primary effects of volcanoes:
-Tephra = solid material ejected into atmosphere, varies in size. Larger particles travel a shorter distance from source, small are thrown into atmosphere and strong winds blow them around the earth, cooling it.
-Pyroclastic flows = Very hot, high velocity, made of gas and tephra. Move at speeds of 700kmh.
-Lava flows = Rarely cause injury due to low velocity, but are unstoppable and can damage buildings.
-Volcanic gases = Co2, CO, H sulphide, chlorine.
71
Give and explain examples of secondary effects of volcanoes:
Lahars = Mudflows, ash + water forms hot, dense, fast moving flows.
Flooding = When an eruption melts glaciers, serious flooding can occur.
Volcanic landslides = Ranges in size 1km3-100km3, high velocity + momentum.
Tsunamis = Sea waves generated by volcanic eruptions.
Acid rain = Volcanoes emit gases (sulphur), combines with moisture and forms acid rain, can blow to other countries as well.
72
Give some physical factors that affect the impact of a tectonic event:
-Distance from epicentre
-Duration of hazard
-Scale + frequency of hazard
-Magnitude of hazard
-Time of day/year
73
Give some human factors that affect the impact of a tectonic hazard:
-Social, economic, political conditions
-Population density
-Methods of coping
-Accuracy in predicting hazards
-Response teams + long term reconstruction
74
Ways of predicting volcanic activity:
-Hazard mapping
-Seismic shockwaves (monitoring earthquakes)
-Gas emissions
-Remote sensing
-Heat emissions
75
Ways of protecting against volcanic activity:
-Warnings issued
-Education for locals
-Hazard mapping
-Land-use planning
76
Signs a volcano may be about to erupt (Preparedness):
-Increase in the release of gases
-Rise in level of lava lakes in volcanic craters
-Bulging upwards of surrounding land due to pressure.
-Increased number of earthquakes.
77
Ways of mitigating the effects of a volcano:
-Risk assessments (Government)
-Diverting lava flow - digging trenches, dropping blocks into lava, using explosives.
-Barriers can be built to protect against Lahars and lava flows.
78
What is a Tsunami?
A wave caused by seismic activity that is caused when an earthquake causes the ocean floor to rise and fall.
79
Why is a tsunami deadly?
They are very fast, occur without warning, very large in height, Long period - 2 deadly waves.
80
Describe the process of Tsunamis travelling from the middle of the ocean to the shore:
-Middle of ocean = Very fast and small, go unnoticed.
-As it approaches the shore, the waves amplify as they slow down.
-Shallower the ocean, friction with ocean floor causes tsunami speed to slow down = amplify and increase in height.
81
What are the warning signs of a Tsunami?
-water draining from sea front
-Seismic activity
82
What and how does the Richter scale measure?
Give an advantage and disadvantage:
-Measures the magnitude of an earthquake by measuring energy waves emitted by the earthquake.
+Simple and easy to understand
-Not useful for earthquakes bigger than Magnitude 8
83
What and how does the Mercalli Scale measure?
Give an advantage and disadvantage:
-Measures the increasing level of intensity of an earthquake based on the effects of the earthquake on people.
+More meaningful to civilians.
-Subjective, some people may exaggerate
84
Define primary impacts
Impacts that are a direct result of the hazard e.g. deaths
85
Define secondary impacts
Occur as a result of the primary impacts e.g. gas pipes break (primary) which cause fires (secondary).
86
process that causes a seismic hazard:
-Tension builds in plate margin
-When tension is released, sends out shockwaves (earthquake).
-Shockwaves spread out from focus
-Type of shockwave determines damage - surface waves = most severe.
-Earthquakes can cause ground to rupture along the fault due to body waves. Causes ground to rise and fall which can sever water, gas etc.
87
Factors that affect the severity of an earthquake:
-Magnitude and depth
-Preparedness, education, protection
-Rural/urban areas
-Distance from epicentre
-Emergency response
-Time of day/year
-Geology
88
(Impact of earthquakes) - Fires:
How do they occur?
-Wooden buildings
-Broken gas pipes
-Power lines
89
What is liquefaction?
When the shaking of the ground causes water logged soil to turn from a solid to a liquid by increasing the space between grains.
90
What is an example of an earthquake where liquefaction occured?
Kobe, Japan (1995)
91
What is a tropical storm?
A revolving, intense, low pressure weather system.
92
Describe the spatial distribution of tropical storms
Found between the tropics. Hurricanes are found South of N America and North of S America. Typhoons are found in SE Asia and travel N across Asia. Cyclones are found N of Australia and E of Africa. However, no tropical storms are found in Europe.
93
Give some facts about the nature of tropical storms (Size, wind speed)
-Re-distribute heat around the world
-Can vary from 200km-700km
-Average wind speed of 75mph
-Eye can vary from 10-15km
-Lifespan = 7-14 days
94
Describe the frequency of tropical storms
Occupy a general season when ocean temps are highest - late summer-autumn. Storms aren't evenly distributed and some places experience more frequent storms than others.
95
How does the Saffir-Simpson Scale measure tropical storms?
Based on wind speeds and has 5 catagories
96
Describe the predictability of tropical storms
Satellite monitoring is more advanced and storms can be tracked over the course of their development. Tracking gets more reliable as storms move closer to land as many storms can change direction whilst over the open ocean.
97
How does the ocean affect tropical storms?
Must be 27 degrees with a depth of 70m - the deep, warm water provides latent heat. This means the ocean provides a continuous source of heat to power the storm.
98
How does atmospheric instability affect tropical storms?
The ITCZ is a narrow zone near the equator where northern and southern air masses converge producing low atmospheric pressure.
99
How does the Earth's rotation affect tropical storms?
Storms are found between 5 and 30 degrees north and south of the equator - this allows the Coriolis force to bring maximum rotation.
100
Give some ways of managing tropical storms:
Preparedness = Education and public awareness, building adaptations, preparing emergency supplies.
Mitigation = Soft engineering schemes can protect against storm surges.
Disaster aid = immediate humanitarian relief e.g. search & rescue, longer term aid that supports recovery and reconstruction.
100
Describe the process of a tropical storm forming
1) Air is heated above the ocean. Warm air rises = low pressure.
2) Rising air draws up more air and large amounts of moisture from the ocean, causing strong winds.
3)Coriolis effect causes air to spin.
4) As air rises it cools and condenses to form large towering clouds which generate rain.
5) Cold air sinks in eye creating an area of high pressure - no clouds so drier and calmer.
6) Storm travels across ocean in prevailing wind.
7) When storm meets land its no longer fuelled by ocean so loses power and weakens.
101
What is an issue with the
Saffir-Simpson Scale?
Doesn't account for rainfall and other factors. So, a low catagory cyclone hitting a densely population area could be far more damaging than a high catagory that hits an urban region.
102
Which direction do tropical storms move in the northern hemisphere?
Spins anti-clockwise and deflects left
103
What direction do tropical storms move in the southern hemisphere?
Spins clockwise and deflect right
104
Give some characteristics of tropical storms
-Storm surges
-Precipitation/lightning
-Strong winds
105
How has climate change affected tropical storms?
Sea levels rise:
-Larger storm surges
-More to evaporate = intensifies quicker.
-More precipitation
-Wind speed increased
106
What are the 3 main types of hazard?
Geophysical = Caused by earth processes. Caused by tectonic activity. E.g. earthquake, tsunami, landslide.
Hydrological = Caused by movement and distribution of surface and underground water. E.g. Flood
Atmospheric = processes operating in the atmosphere resulting in extreme weather/atmospheric conditions.
E.g. Fog, tropical storm, Wildfire, drought, lightning.
107
What does the Degg's model show?
That a a natural event has to be a risk to people and property to be considered a hazard.
108
What is an integrated risk management system?
A plan/process where they identify the risk, analyse and evaluate it, and then treat it. E.g. New Zealand's process of risk management.
109
What are the 4 stages of the hazard management cycle?
Preparedness
Responses
Recover
Mitigation
110
What is plate tectonic theory?
The scientific theory that attempts to explain why the Earth's crust acts the way it does and produces the landforms we can see on the earths surface.
111
How do the plates move at a constructive plate margin?
Away from each other
112
What formations are created at a constructive plate margin?
Ocean ridges = Caused by sea floor spreading. Regular breaks (Transform faults) occur along the ridges.
Rift valleys = Caused by the lithosphere fracturing into sets of parallel faults. The land between these faults then collapses into deep, wide valleys
113
How do the plates move at a conservative plate margin?
Alongside each other at different speeds, either in the same direction or different ones.
114
How do the plates move at a destructive plate margin?
Towards each other
115
What formations occur at a destructive plate margin?
Ocean trench = Caused by plate subduction.
Volcanoes = Subducting plate melts and the resulting rising magma forms volcanoes.
Fold mountains = Sometimes subduction doesn't occur and the colliding plates simply become uplifted and buckle.
116
How do convection currents form?
-Tectonic plates 'float' on the mantle.
-Heat from the core is transferred to the mantle.
-Liquid rick close to the core is heated and rises.
-When it reaches the crust it is forced sideways as often it can't pass through the crust.
-Friction between the convection currents and the crust causes the tectonic plate to move.
-The liquid rock then sinks back towards the core as it cools. Process repeats.
-Tectonic plates move in different directions depending on the direction of the convection currents.
117
Describe and explain each part of the hazard management cycle
Hazard event -
Response = The immediate actions after a hazard event
Recovery = Rebuilding of economy, infrastructure.
Mitigation = Actions taken to reduce the impact of the next hazard event,
Preparedness = education to ensure that people are prepared for future events.
118
Describe risk sharing:
The UNs International Strategy for Disaster Reduction (ISDR) sets out national and international responsibilities in preparing for disasters. Sharing knowledge and human response strategies will enable all countries to prepare for a hazard event in a better way.
Magnitude and intensity of hazards can be reduced depending upon the implementation of mitigation strategies
119
Describe features of a fissure volcano
-Heavy flows of slow moving lava
-Found on constructive plate boundaries
-Produces ryolitic lava
120
Describe features of a shield volcano
-Non-explosive
-Produces fast flowing lava
-Basaltic lava
-Constructive boundary
121
Describe features of a Acid/dome volcano
-Silica rich lava
-Produces pyroclastic flows
122
Describe features of a composite volcano
-Erupts tephra
-Extremely explosive
-Less viscous lava
-Destructive boundary
123
Describe features of an ash and cinder cone volcano
-Erupts tephra
-Produces little lava
-Erupts with bursts of steam and gas
124
Describe features of a caldera volcano
-Result from violent eruptions that blow off the volcanoes summit. This empties the magma chamber, causing the sides to collapse inwards.
-Sends ash columns high
-Large volume pyroclastic flows.
125
Give some physical factors affecting the impact of a tectonic event
Distance from epicentre
Duration and scale of hazard
Time of day/year
126
What is the focus of an earthquake?
The point at which pressure release occurs within the crust - shallower = more destructive.
127
What is the epicentre of an earthquake?
The point directly above the earth's surface where the earthquake occurs.
128
What is a seismic wave?
Waves of energy that travel through the core of the earth carrying energy released from earthquakes.
129
Describe P-waves:
Primary waves:
-Fastest - reach the surface first
-Travel through mantle and core
-Compressional
-Vibrate in direction they are travelling
130
Describe S-waves:
Secondary waves:
-Slower
-Only travel through mantle
-Vibrate perpendicular to direction of travel.
131
Describe L-waves:
Love waves:
-Slowest
-Move side to side
-Cause most damage - surface waves
132
Describe Raleigh waves:
-Radiate from epicentre
-Most shaking felt from earthquake is due to these waves - surface waves
133
Give some primary effects of earthquakes:
Ground shaking
Buildings collapse
Power lines collapse
Liquefaction
134
Give some secondary effects of earthquakes:
Fires caused by broken power lines
Disease spreads from contaminated water
Emergency services hindered
Bodies can't be buried - spreads disease
135
Give some long-term effects of earthquakes:
Loss of farmland and food production
Repairing infrastructure is expensive
High unemployment as businesses are destroyed
Trauma and grief
136
What is a wildfire?
An uncontrolled rural fire. Large, destructive and spreads quickly
137
What is a crown fire?
Spreads across tree canopies and affects forested areas.
138
What is a surface fire?
Burns across surface vegetation
139
What is a Ground fire?
Burns beneath the ground in layers of dry, organic peat.
140
What is the ladder effect?
Describes the process of fires from the forest floor spreading to the tree canopy.
141
What conditions are needed for wildfires to spread?
-Fuel e.g. dry vegetation
-Oxygen
-Heat source - woods flash point = 300 degrees.
-ignition source
-ideal weather conditions
142
Give some physical causes of wildfires
-El nino
-Lightning
-drought
143
Give some human causes of wildfires
Arson
Cigarettes
Campfires
Fireworks
90% of causes are human
144
Describe and explain the distribution of wildfires:
-Some global patterns occur due to natural cycles of rainfall, dryness, lightning e.g. boreal forests of Canada.
-Other parts of the world are due to human activity e.g. S America Aug-Oct, amazon rainforest (Controlled burning).
-Across Africa, a band of widespread agricultural burning sweeps from North to South over the continent as the dry season progresses.
145
What is El nino
a warming of the ocean surface, or above-average sea surface temperatures, in the central and eastern tropical Pacific Ocean.
146
Give some impacts of wildfires:
-Displacement - people being forced to live elsewhere.
-Loss of wildlife - impacts ecosystems and reduces biodiversity.
-Loss of crops, timber, livestock
-Creates pressure for local authorities and governments
147
Give some methods of mitigating wildfires:
-Controlled burning: Removes dead vegetation (fuel). Can get out of control and impacts ecosystems/nutrient cycle.
-Public awareness: Fire bans at times of high risk, Smokey bear character used in USA to encourage responsible fires.
-Early detection: satellites, infrared sensors, cameras.
-Community preparedness: Firefighting volunteers, warning (social media), People may try to establish own defences, cleaning gutters, chopping down trees.
148
Factors which lead to formation of mudflows
Mudflows occur on very steep slopes along the coastline. Where there is limited vegetation to bind the soil together and the ground is very saturated heavy rain can produce sheet flow over the upper cliff surface. The soil continues to be lubricated and it eventually flows over the cliff face and down onto the shore at a fast speed.
149
What is the hazard management cycle
The hazard management cycle is a model that shows how the events of one hazard event inform planning and preparation for the next hazard event
