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Hazards (Earthquakes (Factors that affect the impact of an earthquake…
Hazards
Earthquakes
Physical causes
When the plates are sliding alongside each other and they get stuck it builds pressure underneath the earth's crust. When this pressure is eventually released, and earthquake tends to occur.
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Effects of an Earthquake
Short term
Economic- Shops and businesses are destroyed and there may be some looting. Damage to transport links can make trade difficult.
Environmental- The built landscapes may be destroyed. Fires can spread due to gas pipe explosions and damage the woodlands.
Social- People are killed and injured, and their homes are destroyed. Transportation and communication links may be disrupted. Water pipes may burst and the water may become contaminated.
Long term
Social- Disease may spread and people may have to be rehoused, sometimes in refugee camps
Economic- Cost of rebuilding the settlement is high. Investment in the area may be focused on rebuilding and because of this income may be lost.
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Structure of the Earth
Inner Core
The center of the Earth, it is solid and made up of iron and nickel. WIth its immense heat energy it is like Earth's engine room
Outer Core
The outer layer is the layer surrounding the inner layer, it is a liquid layer also made up of iron and nickel
Mantle
Widest section of the earth, and it is made out of semi-molten rock called magma
Crust
The outermost layer of the Earth, it is the solid rock that we live on
Volcanoes
FORMATION
Magma rises through cracks or weaknesses in the Earth's crust-->Pressure builds up inside the Earth.-->When this pressure is released, eg as a result of plate movement, magma explodes to the surface causing a volcanic eruption.-->The lava from the eruption cools to form new crust.
Over time, after several eruptions, the rock builds up and a volcano forms.
Key Words
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Magma Chamber- collection of magma inside the Earth, below the volcano.
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Flooding and management
Causes of Flooding
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A lack of vegetation or woodland - trees and plants intercept precipitation (ie they catch or drink water). If there is little vegetation in the drainage basin then surface run-off will be high.
A drainage basin, consisting of mainly impermeable rock - this will mean that water cannot percolate through the rock layer, and so will run faster over the surface.
A drainage basin in an urban area - these consist largely of impermeable concrete, which encourages overland flow. Drains and sewers take water quickly and directly to the river channel. Houses with sloping roofs further increase the amount of run-off.
Managing Flooding
Hard Engineering Options
Dam construction
Dams are often built along the course of a river in order to control the amount of discharge. Water is held back by the dam and released in a controlled way. This controls flooding.
Water is usually stored in a reservoir behind the dam. This water can then be used to generate hydroelectric power or for recreation purposes.
Building a dam can be very expensive.
Sediment is often trapped behind the wall of the dam, leading to erosion further downstream.
Settlements and agricultural land may be lost when the river valley is flooded to form a reservoir.
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Soft Engineering Options
Afforestation
Trees are planted near to the river. This means greater interception of rainwater and lower river discharge. This is a relatively low cost option, which enhances the environmental quality of the drainage basin.
Managed flooding
It is also called ecological flooding.
The river is allowed to flood naturally in places, to prevent flooding in other areas - for example, near settlements.
Planning
Local authorities and the national government introduce policies to control urban development close to or on the floodplain. This reduces the chance of flooding and the risk of damage to property.
There can be resistance to development restrictions in areas where there is a shortage of housing. Enforcing planning regulations and controls may be harder in LEDCs.
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