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AQA Geography- Hazards summary notes
AQA Geography- Hazards summary notes Revision notes for hazards
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HazardsHodder (White) Textbook
HAZARDS IN A GEOGRAPHICAL CONTEXT
3.1.5.1 The Concept of Hazard in a Geographical Context
Nature, forms, and potential impacts of natural hazards (geophysical, atmospheric, and hydrological). Hazard
perception and its economic and cultural determinants. Characteristic human responses – fatalism, prediction,
adjustment/adaptation, mitigation, management, risk sharing – and their relationship to hazard incidence, intensity,
magnitude, distribution, and level of development. The Park model of human response to hazards. The Hazard
Management Cycle.
What is a natural hazard?
“A perceived natural event that has the potential to threaten both life and property”- Whittow
A natural disaster occurs as a result of a hazard, when it “causes a significant impact on a
vulnerable population”- Degg
o 10+ people killed, 100+ affected (CRED)
Geophysical- driven by Earth’s own internal energy sources e.g. plate tectonics
Atmospheric- driven by processes at work in the atmosphere e.g. tropical storms, droughts
Hydrological- driven by water bodies e.g. floods, tsunamis
Potential Impacts of Natural Hazards
The risk of the disaster depends on:
o The magnitude/extent/duration of the hazard
o The vulnerability of the people affected
o The capacity of a society to cope
Primary impacts have an immediate effect on the affected area e.g. destruction of buildings
Secondary impacts happen after the disaster has occurred e.g. disease, economic recession
A natural event becomes a hazard when there is the presence of people
Increasing population and therefore demand for land has resulted in building in areas with
increased risk
Natural disasters in HICs do little long-term damage to the economy because there is enough
wealth to be able to rebuild infrastructure
LICs rely more on support and aid to repair
Human Responses
Local level- saving possessions and safeguarding property
Global level- coordinating rescue and humanitarian aid
The intensity of the event and the original state of the infrastructure affects the speed of
international response
Automatic Disaster Analysis and Mapping system (ADAM) has reduced the response times to
disasters
o It is a database that pools information from the US Geological Survey, World Bank and
World Food Programme
Characteristic human responses –
o Fear and Dread
o Fatalism
Accepting that hazards are natural (fate) so we can do little to control and losses
have to be accepted
o Prediction
Remote sensing and seismic monitoring give clues of activity that may lead to a
disaster and should be acted upon
Advances in communication
, o Adjustment/adaptation
Once we accept natural events are inevitable, we can adapt our behaviour so
losses can be kept to a minimum
Most realistic option and is more effective and cost-effective
o Mitigation and management
o Risk sharing
The measures that a society puts in place to reduce the loss of life and property
damage through
1. Public education and awareness programs
2. Evacuation procedures and provision of emergency medical supplies
and food.
3. Use of financial mechanisms such as insurance to support losses (In
HICs/NEEs and international aid in LICs)
Responses to tectonic hazards
People cope with natural hazards in very different ways
The chosen ways are often related to wealth 9iq1and access to technology
Humans have a capacity to ignore or seriously underestimate risk, even when it seems obvious
to others
The Park Model of human responses to hazards
The type of disruption to life after a hazard depends on different factors and the park model
describes 3 phases:
1. Relief: the immediate local and possibly global response in the form of aid, expertise and
search and rescue.
2. Rehabilitation: a longer phase lasting weeks or months, when infrastructure and services
are restored, albeit possibly temporarily, to allow the reconstruction phase to begin as
soon as possible.
3. Reconstruction: restoring to the same, or better, quality of life as before the event took
place.
Likely to include measures to mitigate against a similar level of disruption if the
event occurs again.
The steepness of the downward curve during disruption
depends on the nature of the event.
o E.g. Earthquake = immediate disruptive impacts
o Volcano = warning (so preparations can be made to
mitigate the impacts= less steep curve)
The depth of the curve is a factor of the scale of the
disaster, which is dependent on the magnitude of the event
and the nature of the locality. (No fixed pathways at the end).
The Hazard Management Cycle
Large-scale events can rarely be Speed of response
prevented from happening depends on
Education & raising public effectiveness of the
awareness reduces the human emergency plan
causes & adjust behaviour Immediate responses
which minimises impact HAZARD focus on saving lives &
Knowing what to do in the MANAGEMENT medical assistance
CYCLE
immediate aftermath speeds up Damage assessment
recovery helps plan for
High risk areas will be greater recovery.
prepared
, Aims to reduce severity of an event and its Restoring the affected area to
impacts something approaching normality.
Involves direct intervention e.g. building design Short term- restoration of services
that can withstand earthquakes so planning and reconstruction for
Most desirable is the long-term protection of the pre-event levels can begin.
natural barriers e.g. coral reefs (protect the
shore against storm surges)
THE STRUCTURE OF THE EARTH
3.1.5.2 Plate Tectonics
Earth structure and internal energy sources.
Earth structure and internal energy
Edmond Halley suggested that the earth was made up of hollow spheres (like Russian dolls)
He said that each layer was habitable (we know now it’s not)
Earth is actually a geoid (bulges at equator, flattens at poles) due to centrifugal forces
generated by the Earth’s rotation which fling the semi-molten interior outwards
The crust
Oceanic crust
Primarily basalt (silica and magnesium: SIMA)
4-7km thick (thin relative to continental)
Denser (heavier) than continental
Younger as more of it gets destroyed
Continental crust
Primarily granite (silica and aluminium: SIAL)
20-70km thick
Less dense (will not undergo subduction)
The lithosphere
The crust and upper mantle are known as the lithosphere
It is here where tectonic plates are formed
The mantle
Thickest section (2900 km)
Due to the great heat and pressure, the silicate rocks are in a thick, liquid state (denser with
depth)
Rocks in mantle are solid and sit on top of the asthenosphere (layer of softer, plastic like rock)
Asthenosphere moves very slowly carrying the lithosphere on top
The Core
4x as dense as the crust
Core’s internal heat is the major cause of the earth’s activity
Outer core
Semi-liquid iron
As the earth rotates, the liquid outer core spins creating the magnetic field
Inner core
Solid iron-nickel alloy
Earth’s Heat
The heat from the earth’s interior comes to the surface from 2 sources (equal amounts):
1. Radiogenic heat- produced by the radioactive decay of isotopes in the mantle and crust.
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