GeographySPEC B unit 1 (restless planet)

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  • Created by: Prachanna
  • Created on: 28-03-13 22:28

The Earth in Cross-section

Layers in the earth - crust,asthenosphere, upper mantle, lower mantle, outer core, inner core.


Lithosphere - Continetal crust, Oceanic Crust and Upper Mantle

Mantle- Asthenosphere and Lower Mantle

Core - Outer Core and Inner Core

Types of Crust

Continetal crust - This is made up of a realtively less dense rock called granite. This is a thick rock.

Oceanic Crust - This made up of a more denser rock called basalt and is much thinner than the continental crust.These crusts are broken up into plates

Convection currents 

 In the Mantle it can reach High temperautre this is caused by radioactive decay releade by the core. This can cause rock material to heat up and rise, as it ises and reaches the surface of the asthenosphere (partially molten rock acts as base for plates) the rock particles spread out along the surface and when the start to lose their heat the then come back done to the centre of the mantle. This is a recurring cycle that goes on and on. This can put pressure on the plates above causing them to move.

 Plate Boundaries

Constructive Margins:

When two plates ( oceanic crusts) are pulled apart by the covection currents,at the opening of the vent, it causes magma to rise and this can form a volcano. When the magma rises it spreads out and it becomes a new base and the spread the seafloor further.

E.G. - The Eurasian plate is slowly spreading away from the North-American Plate in the mid-Atlantic.

 Destructive Margins:


When an oceanic crust and a continental crust both are colliding the more heavier and denser oceaic crust is caused to sink under the lighter continetal crust -- this process is known as subduction. Because the oceanic crust sinks into the mantle the pressure and great heat causes the crust to melt casung the rock to become magama again. However because some lighter rock materials rise as



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