Restless Earth Notes

notes on restless earth geography aqa a

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Central zone
Concentration of iron and nickel
Semi molten magma
Convection currents determine direction of plate movement
The Crust
Thin outer layer
Split into plates
Continental Crust
Older most over 1500mill years old
Less dense
Cannot sink
Cannot be renewed or destroyed
Oceanic crust
Newer most less than 200mill years old
Can sink
Can be renewed and destroyed
Destructive plate margins
As the two plates collide, the heavier oceanic plate sinks beneath the lighter continental plate.
Friction between the plates generates heat, causing the continental plate to melt, forming magma.
A fault occurs and magma escapes to the surface, to form a volcano. As the plates rub together, vibrations
cause earthquakes.
The continental crust buckles to form mountains.
When two continental plates collide mountains are formed.
Constructive plate margins
Plates move apart
Pressure is released from mantle
Magma escapes to surface
Volcanoes are formed, many underwater
New land is formed, creating a midocean ridge

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Conservative plate margins
Best example at San Andreas Fault, California
North American Plate and Pacific Plate both move in same direction, but at different speeds.
Friction prevents easy movement, stress and strain build up and pressure is released with a sudden jerk,
causing an earthquake
Ocean trenches
Deepest part of ocean
Found where an oceanic plate is sinking below a continental plate
Both fold mountains and ocean trenches form when plates converge. If they occur together it is due to
subduction.…read more

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Farming Subsistence farming. Steep slopes are terraced to create areas of flat land these also prevent
soil erosion and retain rain water. Some cash crops, e.g. rice and cotton. Llamas are used for meat, milk,
transport and wool.
Mining Many minerals minded e.g. tin silver gold. 50% of Peru's exports are from mining. Yanacocha gold
mine is biggest gold mine in the world. This creates jobs but can increase crime.
HEP Uses flowing water to generate electricity.…read more

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Forests flattened.
Secondary effects:
1) Floods because ash blocked rivers
2) Air space closed
3) Bridges and roads damaged.…read more

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Longitudinal waves cause up and down movement.
Transverse waves cause side to side movement more damage
Primary waves these travel fastest and cause back and forth movement
Secondary waves slower and cause side to side movement
Richter scale:
Measures movement of the ground. A logarithmic scale (3 is 10 times bigger than 2). No upper limit.
Mercalli scale:
Measures effect of earthquakes observed by people. Very subjective (people may exaggerate). Not
mathematical, on a scale of 1 to 12. 12 is total destruction.…read more

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Sichuan, China, 2008
Primary effects:
1) 69,000 died
2) 400,000 injured
3) 5 mill buildings collapsed
Secondary effects:
1) Landslides
2) Floods
3) Lots made homeless
4) Telephones didn't work
Immediate Responses:
1) Troops came in by helicopter
2) International aid from Russia and Japan
Long term responses:
1) Debts cancelled by banks
2) Temporary homes built
3) Red Cross raised money
4) Took 3 years to recover
Attempting to forecast and earthquake. We know where, just not when.…read more

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Streets littered with bodies
8) Disease spread
9) Farmland and crops destroyed
Short term response:
1) Hundreds of millions of pounds pledged by foreigners
2) Soldiers, nurses, etc sent to help.
Long term response:
1) Billions pledged to rebuild infrastructure
2) Programmes set up to rebuild
3) Warning system developed
4) People trained for if it happens again.…read more


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