Geography AQA GCSE
All content in the first third of Paper one Content.
Everything you need to know about Hazards, with adequate detail.
Includes extra detail and visual guides.
Hazards
1.1
Definition of a natural hazard:
A naturally occurring (not caused by man) threat that has the potential to cause loss of life, injury,
property damage or disruption to way of life.
Natural Disaster: A major hazard event that causes widespread disruption to a community or region that
the affected community is unable to deal with adequately without outside help.
Disaster: An event which has occurred and caused harm. According to the UN, a disaster means 10
people have died/ 100 people injured/ state of emergency declared.
Types of hazard:
1) Tectonic risk , Earthquake and Volcanoes, their primary and secondary hazards
2) Atmospheric hazards, mostly tropical storms and flooding in the UK
3) Climate Change, also known as Global Warming.
Factors affecting hazard risk:
● Population density: Should a natural disaster strike a city or place of high population density the
injuries, deaths and total insurance costs are sure to be higher than unpopulated areas.
● Size of hazard: Clearly larger hazards have more potential to cause damage than small ones.
Hurricanes with a wind speed of around 74 mph will do far less damage than category 5
hurricanes (over 150mph)
● Time of day: Less important than others, but important If an earthquake were to strike during
rush hour the impacts will be greater than on a bank holiday when people are at home.
● Wealth of country (HICs and LICs and NEEs) A country's wealth and development will directly link
to how prepared they are for the hazard, LIC will be aware of the risk but may not have the funds
to invest in the things needed to protect themselves. HIC’s will invest heavily in earthquake proof
technology to protect lives and buildings.
1.2
Plate tectonic theory:
Plate Tectonics and volcanoes are closely linked; most of the world's volcanoes occur along the earth's
plate boundaries.
Plate Tectonic theory explains how the heat generated within the earth's interior causes volcanoes,
earthquakes, breaks up continents and causes continents to collide again:
Beneath our feet the earth's crust is sliding around on the hot rocks of the earth's interior.
The earth's crust is split into large rigid slabs of rock called tectonic plates.
The slabs are the cooled outer layer of the earth and beneath them lies the mantle, a very hot layer of
rock on which the plates float.
Beneath the mantle is the earth's core which generates vast quantities of heat.
The heat causes convection currents which move the earth's plates around the cross section through the
earth's crust.
The earth's tectonic plates, which make up the earth's crust, float upon the hot rocks of the mantle below.
Although solid the mantle moves due to enormous convection currents caused by the heat from the
earth's core.
The mantle flows and moves, despite being solid.
Oceanic crust is created at the mid ocean ridges and then travels towards the subduction zones where it
sinks back into the mantle.
, Types of plates:
Plate boundary diagram description What happens Global examples
type
destructive Oceanic plate Oceanic plate is Pacific plate is
being subducted under a subducted under
subducted continental plate Eurasionplate,
beneath because the oceanic forming
another plate. plate is heavier, and the volcanoes on
plate gets pushed/pulled Japan and deep
into the mantle where it trench to the east
is destroyed by very high of japan.
heat and pressure. They
result in earthquakes,
trenches and composite
volcanoes
constructive Two plates Two plates move apart Mid Atlantic ridge
move away caused by heat raising and Iceland is a
from each from inside the mantle. volcanic area
other. Lava pushes up between formed from the
the 2 plates forming a Mid Atlantic ridge
new crust. They result in becoming
earthquakes, ocean pushed above
ridges, and cone the sea levels.
volcanoes
conservative Two plates The plates are moving North American
move past past each other. plate and Pacific
each other. Pressure builds up as the plate. San
plates rub past each Andreas fault
other. Plates will stick, plates move in
pressure builds and is the same
suddenly released, direction but one
resulting in an is moving faster
earthquake. than the other.
Volcanic Hazards:
● Volcanic ash is a fine-grained, abrasive mixture of rock, volcanic glass and mineral fragments.
The harmful gases within volcanic ash can cause respiratory and eye problems, water
contamination and reduced visibility.
● Lahar is a violent mudflow made of pyroclastic material, rocky debris, ash and water.They are
extremely destructive due to their flow rate, and can reactivate once stopped when in contact with
water.
● Lava is magma on the surface (of the Earth), that despite being extremely slow-flowing, is
excessively hot: from 750℃-1,200℃.
2
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