Geography - Restless Earth AQA

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Tectonic Plates

The outer layer of the earth is the crust. It is divided into lots of slabs called tectonic plates. Plates are made of two types of crust - continental and oceanic:

  • Continental crust is thicker and less dense
  • Oceanic crust is thinner and more dense

The places where plates meet are called plate margins. There are three types of plate margins:

  • Destructive Margins - Where two plates are moving towards each other. When an oceanic plate meets a continental plate, the denser oceanic plate is forced down and destroyed. This often creates volcanoes and ocean trenches. When two continental plates meet, the plates smash together, but no crust is destroyed
  • Constructive Margins - Where two plates are moving away from each other. Magma rises from the mantle to fill the gap and cools, creating new crust
  • Constructive Margins - Where two plates are moving sideways past each other, or moving in the same direction but at different speeds. Crust isn't created or destroyed
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Fold Mountains

When tectonic plates collide the sedimentary rocks that have built up between them are folder and forced upwards to form mountains

So fold mountains are found at destructive plate margins and places where there used to be destructive margins

You get fold mountains when a continental plate and oceanic plate collide and when two continental plates collide

Fold Mountains are used for:

  • Farming - Higher mountain slopes are great for growing crops
  • HEP - Steep sided mountains and lakes are great for generating HEP
  • Mining - Fold mountains are a major source for metal ores
  • Forestry - Fold mountains ranges are a great environment for growing tees
  • Tourism - Fold mountains have spectacular scenery which attracts a lot of tourists
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Fold Mountains Case Study - Alps

The alps is located in central Europe with its tallest peak being Mont Blank and has a population of around 12 million people.

People use the Alps for lots of things including:

  • Farming - The steep areas are used to farm goats, which provide milk and cheese
  • HEP- The narrow valleys are dammed to generate HEP which is used to produce electricity for local homes
  • Mining: Salt, iron ore, gold, silver and copper were all mined in the Alps
  • Forestry - Scots pine is planted all over the Alps as it stops the goats munching at the trees
  • Tourism - 100m tourists visit the Alps each year and 70% of them visit the mountains

People have to adapt to the conditions of the Alps:

  • Steep-Relief - Goats are farmed there because they're well adapted to live on steep mountains.  Trees and man made defences are used to protect against avalanches and rock slides
  • Poor Soils - Animals are put in the high areas as the soil isn't great for growing crops
  • Limited Communications - Tunnels have been cut through mountains to provide fast transport links
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Earthquakes are caused by the tension that builds up at all three plate margins:

  • Destructive - tensions builds when one plate gets stuck under the other
  • Constructive - tension builds up within the cracks of the  plates as they move away from each other
  • Conservative - tension builds when plates grind that grind past each other get stuck

The plates eventually jerk past each other, sending out shockwaves which is an earthquake. The shockwaves spread out from the focus

Earthquakes are measured by:

The Richter Scale - This measures the energy released called magnitude which is measured by a seismometer

The Mercalli Scale - This measures the effect of the earthquake by eyewitness form 1-12

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Earthquake Case Study - Kobe, Japan

Immediate effects:

  • Over 6,000 deaths
  • 300,000 homeless

Secondary effects:

  • Over $200 billion damage
  • Fires spread across the city

Immediate responses:

  • Emergency services put out fires and searched for survivors
  • Friends and family searched for loved ones
  • People had treatment in hospital corridors because of the large numbers

Long term responses:

  • Road network restore in 6 months
  • Buildings built to absorb earthquakes
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Earthquakes Case Study - Haiti

Immediate effects:

  • 316,000 deaths
  • 1,000,000 homeless
  • The capital cites prison was destroyed, freeing 4,000 inmates to escape
  • Estimated 3million people were affected by the Haiti earthquake

Immediate responses:

  • Bodies were buried in mass graves while others were burned
  • Slow distribution of resources resulted in people looting
  • Appeal videos from celebrates

Long term responses

  • Information given about how to survive future disasters
  • Improved drugs and medicines to treat people
  • Water supply was improved
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Volcanoes are found at Destructive and Constructive plate margins


  • The oceanic plate goes under the continental plate as it is more dense 
  • The oceanic plate moves down into the mantle, where its melted and destroyed
  • A pool of magma forms
  • The magma rises and erupts onto the surface forming a volcano


  • The magma rises into the gap created with the two plates moving away from each other forming a volcano

There are different types of volcanoes:

Composite - Made of ash and lava that's erupted, cooled and hardened into layers. The lava is usually thick and flows slowly. It hardens quickly to form a steep-sided volcano

Shield - Made up of lava only. The lava is runny. It flows quickly and spreads over a wide area, forming a low flat volcano

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Volcano's Case Study - Mount St Helen's

Cause - Destructive plate margin Juan de Fuca and North American plate

Immediate responses:

  • Helicopters for search and rescue
  • 2 million face masks sent to the area

Long term responses:

  • Rebuilding of bridges, roads and buildings
  • Replacing of fallen trees

Immediate effects:

  • The pyroclastic flow wiped out all living things 27km north
  • 57 people died

Long term effects:

  • A huge loss in the economy
  • Landscape changed dramatically
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Supervolcanoes are huge volcanoes that develop at destructive plate margins or over parts of the mantle that are really hot called hotspots. e.g. Yellowstone in the USA is on top of a supervolcano. Here's how they form at hotspots:

  • Magma rises through the cracks in the crust to form a large magma basin below the surface. The pressure causes a circular bulge on the surface several kilometers wide
  • The bulge eventually cracks, creating vents for lava to escape. The lava eruptes causing earthquakes and sending up gigantic spews of ash and rock
  • As the magma basin empties, the bulge is no longer supported so it collapses spewing up more lava
  • When the eruption is finished there is a big crater left where the bulge collapsed called a caldera

When it erupts...

  • It will throw out out thousands of kubic kilometers of rock, ash and lava
  • A thick cloud of super heated gas and ash will flow at high speeds, killing and burning everything it touches
  • Ash will shoot kilometers and almost  block out the sun which can cause ice ages
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Tsunamis Case Study - Indian Ocean

A tsunami is a special type of wave where the entire depth of the sea is displaced. This occurs from an event like an earthquake and volcano out at sea

Indian Ocean Tsunami - Occurred on 26th December 2004 were there was an earthquake on a destructive plate margin in the Indian Ocean, measured 9.1 on the Richter Scale

Immediate effects:

  • Over 220,000 deaths
  • 2 million homeless

Immediate responses:

  • Rescue services swamped by scale of disasters
  • International aid was immediate, providing fresh water, food, tents and raised millions of money

Long term responses:

  • Indian Ocean Tsunami warning system set up in 2006
  • £372 million donated by the British public
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