The Restless Earth

The Restless Earth

1. Plate Margins

   • Destructive
     • Plates move towards each other.
     • Oceanic crust forces underneath continental crust.
       • This is called 'subduction' and it occurs are a 'subduction zone.'
     • Oceanic melts into the mantle.
     • As the crusts rub against each other they cause friction.
     • Rock is destroyed.
     • Collision Zone
       • Two continental plates collide.
         • Neither is forced under so they're forced uupwards.
   • Constructive
     • Plates move away from each other.
     • Happens between two pieces of continental crust.
     • As they move apart due to the convection currents in the mantle, the gap is filled by magma.
       • Magma then cools and solidifies.
     • Can lead to the creation of ocean ridges.
   • Conservative
     • Plates slide past each other.
       • - At different speeds in the same direction.
         • or - In opposite directions.
     • Plates often get stuck, building up pressure that often causes powerful earthquakes.
     • No rock is created or destroyed.

2. Landforms

   • Fold Mountains
     • Occur at collision boundaries
     • See notes page for formation and uses.
       • Fold Mountains
   • Ocean Trenches
     • Occur at destructive boundary at the subduction zone.
     • Often near fold mountains.
     • Widely found in the Pacific Ocean.
   • Supervolcanoes
     • Capacity to erupt x100 more material than normal volcano.
     • Flat and wide.
       • Often found under the ocean.
     • Has a caldera instead of a crater.
       • Depression in the top.
   • Volcanoes
     • Composite
       • Alternating layers of lava and ash.
       • Usually found at destructive boundaries.
       • May erupt pyroclastic flow instead of regular lava flow.
       • Tall and steep.
       • Formed by thick, viscous lava.
     • Shield
       • Low, gentle sloping.
       • Usually found at constructive boundaries.
       • Frequent but gentle eruptions.
       • Formed by thin, runny lava.
     • Vents
       • Main - main place for magma to escape.
       • Secondary - this vent opens in the first becomes blocked.
     • Can be:
       • Dormant - temporarily inactive
       • Extinct - Never likely to erupt again.
       • Active - erupts frequently.

3. Earthquakes

   • Can happen at any boundary, most common at conservative.
   • Focus - point under the earth where the pressure is released.
   • Epicentre - directly above focus on surface of the Earth.
   • Seismic Waves - release of the energy.
   • Richter Scale
     • Uses information collected by seismometers which collect information on the amount of movement and the strength of the shock waves.
     • 0 - Infinity
       • No upper limit.
     • 10 fold. Each number on the scale is x10 more powerful than the previous.
       • eg. 2 is x10 more powerful than 1.
   • Mercalli Scale
     • Measures earthquake by damage.
     • 1-12 / I-XII
       • 1 - barely felt. 12 - total destruction.
     • Can be represented as pictures/diagrams.
   • Effects
     • Effects of Natural Disaster
     • Aftershocks can cause more damage.
   • Response
   • Tsunami
     • The entire depth of the sea is set in motion by an event, displacing the water above it and creating a wave.
     • One plate is dragged under another, stress on the boundary causes the edges to flex and deform.
       • The plates flex back into their original place, displacing all the water above.

4. Crusts

   • Oceanic
     • 5-10km thick.
     • More dense.
   • Continental
     • 25-100km thick.
     • Less dense.

Images and files in the map