Restless Earth

Restless Earth

1. Plate Boundaries

   • Destructive Plate Boundary
     • Volcanoes are formed and Earthquakes take place
     • The much denser Oceanic Crust is forced underneath the Continental Crust. This is called the Subduction Zone
       • If two Continental crusts are forced together, Mountain ranges such as the himalayas are formed
   • Constructive Plate Boundary
     • The Oceanic Crusts move apart
     • Volcanoes are formed
   • Conservative Plate Boundary
     • The plates slide past each other
       • They move in the same direction, opposite directions and at different speeds
     • Earthquakes take place when the plates get stuck. When they slip an Earthquake is caused
     • An example is the San Andreas Fault in California
   • Collision Plate Boundary
     • Plates move together
     • No volcanoes are formed
     • Both Continental Crust that move together, Have similar densitys
     • Fold mountains created when plates buckle- Himalyas

2. Structure of the Earth

   • The crust
     • Outer layer of the Earth. It is a thin layer, between 0-60km thick and is a solid layer of rock
     • Two types of crust. Continental Crust which carries Land and Oceanic Crust which carries Water
   • The Mantle
     • Widest section of the Earth. Thickness of appoximately 2,900 km. Made up of semi-molten rock called magma
     • In the upper mantle, the rock is hard. In the lower mantle the rock is soft and begins to melt
   • The Core
     • Outer core is made from Iron and Nickel and is liquid. The Inner core is also made from Iron and NIckel but is solid
     • Centre of the Earth
     • The Inner core has a temperature of up to 5,500 degrees and with its immense heat energy it acts as the engine room of the Earth
     • The Outer Core is the layer surrounding the Inner Core. It has a similar temperature to the Inner Core
   • Convection Currents
     • A current of warm material that rises beneath plates and makes them move
     • When Convection Currents diverge (Seperate) near the Earth's crust, Plates move apart (Constructive Plate Boundary)
     • When Convection Currents coverge (Move together) the plates move together (Collision Plate Boundary)
     • The radioactive decay that is happening in the core heats up the mantle which rise as it is less dense. The semi-molten rock spreads out and carries the plate above with it
     • The sideways motion moves the crusts plate. After movement, the mantle cools and sinks back down to be reheated in the core.

3. Volcanoes

   • Composite Volcanoes (Cone Volcanoes)
     • Steep-Sided, Symmetrical cone shape, HIgh with a narrow base
     • Alternate layers of acid, lava and ash
     • Eruptions are usually very explosive because gas builds up under pressure and then is released very suddenly with great force
     • Less frequent eruptions
   • Shield Volcanoes
     • Wide base, Gentle Slopes
     • Made up of hardened lava
     • Lava is more runny so it flows quicker. This runny lava spreads quickly over a wide area, forming a low, flat volcano
   • Dome Volcanoes
     • Made up of layers of hardened lava
     • The lava is thick and slow flowing, Rapidly cools
     • The lava hardens quickly so they have steep, convex slopes
     • Narrow base and high cones
   • Pyroclastic Flow
     • A pyroclastic flow is a fast moving current of superheated gas and rock
     • It can reach up to speeds of 450mph and 1000 degrees
     • The flow normally travels downhill. The steeper the gradient, the faster the flow
     • The flow is the result of the plume of the volcano losing pressure and collapsing

4. Super Volcanoes

   • Cover a larger area than normal Volcanoes
   • Much bigger but much flatter than normal volcanoes
   • Do not have a crater, Have a caldera instead
   • Ash from an eruption settles over hundreds of square kilometres

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