UNIT 1

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  • Created by: MahdiyatJ
  • Created on: 07-05-16 17:01

The Structure of the Earth

Inner core - This is the centre of the earth where it is the hottest. it is solid and consistes of iron and nickel with temperatures of upto 5000oc.

Outer Core – This is a liquid layer also composed of Iron and Nickel and is extremely hot with temperatures similar to the inner core.

Mantle – This is the widest section of the Earth at approximately 2,900km. It is made up of semi-molten rock called magma. Towards the top of the mantle the rock is hard, but lower down nearer to the centre of the earth the rock is soft and beginning to melt.

Crust – This is the thin outer layer of the earth which is only between 0-60km thick. The crust is the solid rock layer which we live on. There are two different types of crust:

  • Continental Crust – Carries land
  • Oceanic Crust – Carries water
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The Plate Boundaries

Destructive - Where two plates collide and one plate flows beneath the other – subduction. - Earthquakes and volcanoes occur here - E.g.: Nazca Plate and South American Plate

Constructive - Rising convection currents pull crust apart forming volcanic ridge - Mid-Atlantic Ridge - E.g.: Eurasian and North American Plates

Conservative - Two plates slide past each other - Earthquakes occur here - E.g.: San Andreas Fault, California

Collision - Two continental plates collide and the two plates buckle - Many earthquakes occur here - E.g.: Indo-Australian and Eurasian plates

Continential Drift Theory: Alfred Wegener                                                                       > Scientists know that the continents were once all joined together. They formed a supercontinent called Pangea.

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Volcanic HazardsShield Volcano... Composite Volcan

Shield Volcano...

  • Are found on constructive plate boundaries
  • Are formed by eruptions of thin, runny lava which flows a long way before it solidifies
  • Have gentle sloping sides and a wide base
  • Contain basaltic magma which is very hot with low silica and gas content
  • Erupt frequently but not violently

Composite Volcanoes...

  • Are found on destructive plate boundaries
  • Are formed by eruptions of viscous, sticky lava and ash that don’t flow far
  • Have steep sloping sides and a narrow base
  • Made up of layers of thick lava and ash
  • Contain andesitic magma which is less hot but contains lots of silica and gas
  • Erupt infrequently but violently, including pyroclastic flows (mix of ash, gases and rock)
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Kashmir, Pakistan 2005

Primary effects

  • Buildings collapsed
  • 75,000 people killed landslides and large cracks appeared on the grounds

Secondary effects

  • Broken sewage pipes contaminated water supplies and spread diseases
  • People died of cold due to weather

Short term responses

  • The army and emergency services arrived to join the rescue effort
  • Aid workers arrived from aboard to help out

Long term responses

  • School and hospitals were rebuilt
  • Building regulations were improved to reduce future damage
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Fukishima, Japan 2011

Primary effects

  • 2 million left homeless because of the Tsunami
  • 15.400 people were killed

 Secondary effects

  • 500,000 were forced to live in shelters
  • The damage underground on gas pipes led to fires which spreaded quickly

Short term responses

  • A tsunami warning was issued 2 minutes after the earthquake  
  • 230 emergency teams were mobilised

Long term response

  • Thousands could not escape due to the tsunami
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How can Earthquake damage be reduced?

what makes and earthquake proof building?

  • A damper in the roof acts like a pendulum reducing damage to building  
  • Cross braking stops floors from collapsing
  • Shock absorbs built in cross brakes
  • A strong steel frame which is also flexible, stops cracking
  • Strong double glazed windows broken glass shattering down
  • Very deep foundation to prevent collapse
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