Hazards Flashcards
What is a natural hazard?
events that are perceived to be a threat to people, the built environment and the natural environment.
Explain the difference between a hazard and a disaster:
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.
Features that help define events as natural hazards:
-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.
Define perception
The way that people view the threat of a hazard event. This will determine the course of action or response.
Factors that influence perception:
-Socio-economic status
-level of education
-employment status
-religion/culture
-family/marital status
-past experience
-values/personality
Define fatalism (Perception)
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.
Define adaptation (Perception)
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.
Define fear (Perception)
Perception of a hazard in which people fell so vulnerable that they can’t face living there and will move away.
How are Hurricanes measured?
Saffir-Simpson hurricane wind scale
How are earthquakes measured?
Richter scale
How are wildfires measured?
Flame characteristics and rate that energy is released
Reasons people may put themselves at risk of a natural hazard:
-hazards are unpredictable
-Lack of alternatives
-Changing level of risk - overtime places that were once safe are now dangerous.
-Cost/benefit
-Perception
What is the equation to measure risk?
(Frequency/magnitude of hazard x vulnerability) /divided by/ capacity to cope or adapt.
Where can responses to natural hazards come from? (List)
-individuals
-local community working together
-national government
-international agencies
Define community resilience
the sustained ability of a community to utilise available resources to respond to, withstand and recover from the effects of natural hazard events.
Define prediction
Give warnings where possible, improved monitoring.
The issue with prevention:
very difficult and unrealistic
Define protection
Protecting people, possessions, built environment by modifying the environment. Also educate people, evacuation programmes.
Define integrated risk management
The process of considering the social, economic and political factors involved in risk analysis and deciding on actions that need to be taken.
Factors that hazard response depends on:
-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
What does the park model show?
The strategies and approaches taken to being ‘back to normal’ after a disaster. The curve demonstrates the scale of the disaster.
Give examples of relief
Search, rescue, care operations take place. Medical supplies, rescue equipment, expertise, clothing and food may be flown in. Potentially local and global response.
Describe rehabilitation
Can last weeks or months. Restore physical and community infrastructure/services. More complex, requires assessment of needs and coordinated planning of resources.
Describe reconstruction
Permanent changes are introduced, which are the same or better QOL and economic stability than before.
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.
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
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.
Positive implications of mitigating ‘super catastrophes’:
-Reduced death toll
-Reduced impact on infrastructure
-Reduced cost for long term response
What is the thickness of the mantle?
2900km
Describe the inner core
-Solid
-iron-nickel alloy
-Can reach 5000 degrees C
Describe the outer core
-Semi-liquid
-Mainly iron
-Can reach 5000 degrees C
What elements is the oceanic crust made of?
Silica and magnesium (SIMA)
What is the thickness of the oceanic crust?
5-10km (denser)
How old is the oceanic crust?
less than 200 mill yrs old (young)
What elements is the continental crust made of?
Silica and aluminium (SIAL)
What is the thickness of the continental crust?
20-70km
How old is the continental crust?
3.8 billion yrs old (older)
What is the Asthenosphere?
Lies beneath the lithosphere, is semi-molten on which plates float and meet.
What is Rheid?
A non-molten solid that deforms by viscous or plastic flow, in response to an applied force.
What is continental drift?
The theory that the continental landmasses have changed position over time, created by Alfred Wegener (1912).
What are the names of the 2 continents Pangea became?
Laurasia and Gondwanaland
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.
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.
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.
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.
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.
How quickly do tectonic plates move per year?
2cm-16cm
What evidence do we have that subduction occurs?
Ocean trenches and that the earth isnn’t getting any bigger. Therefore, as plates are made, other plates must be subducting and being destroyed.
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.
What is magma?
Molten rock that is found beneath the surface of the earth.
What is igneous rock?
Rock that is formed when magma cools.
What is intrusive magma?
Magma deep in the earth
What is extrusive magma?
Magma above the earth’s surface
What is ridge-push?
Gravity acting on the weight of the lithosphere pushes the older part of the plate away from the ridge.
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.
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.
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.
What is a mantle plume?
An upwelling of abnormally hot rock within the earth’s mantle, thought to be the cause of hotspots.
What is a volcano?
A vent (opening) in the earths crust through which lava, tephra and gases erupt.
What is Tephra?
Ash, dust, fragments of material produced in a volcanic eruption.
