The restless earth

The restless earth

1. Structure of the earth

   • Inner core
     • Solid (iron and nickel)
   • Outer core
     • Liquid (iron and nickel)
   • Mantle
     • The dense, mostly solid layer between the outer core and crust (plastic)
   • Crust
     • Continental
       • Older, mostly 1,500,000,000
       • Less dense
       • Can't sink
       • Cannot be renewed or destroyed
       • Mainly granite
       • 35% surface
     • Oceanic
       • Newer, most less than 20,000,000yrs
       • Denser
       • Can sink
       • Can be renewed/destroyed
       • Mainly basalt
       • 60% earth's surface

2. Plate margins

   • Destructive
     • Subduction
       • One sinks under another
       • Pacific + Indo-Australian
     • Collision
       • Two continental push into each other
       • Eurasian + African
   • Constructive
     • Two plates move away from each other
     • South American + African
   • Conservative
     • Two plates slide alongside each other
     • Pacific + North American

3. Volcanoes

   • Composite
     • Eruptions infrequent but often violent
     • Steep slopes and narrow base
     • Secondary cones and layers of thick lava and ash
     • Destructive plate boundaries
   • Shield
     • Low, rounded peak
     • Wide base and gentle slopes
     • Layers of runny lava, little ash
     • Constructive plate boundaries
     • Eruptions frequent and not violent

4. Supervolcanoes

   • A mega colossal volcano that erupts at least 1000km3 of material. (Mt. St. Helens only erupted 1Km3)
   • Large depressions called calderas often marked by a rim of higher land around the edges
   • 1) Rising magma cannot escape and a large bulge appears on the surface
     • 2) Cracks appear in the surface and gas and ash erupt from the magma chamber
       • 3) the magma chamber collapses, forming a depression called a caldera
   • Yellowstone effects
     • National
       • Destroy 10,000Km2 of land
         • Kill 87,000 people
       • 15cm of ash would cover buildings within 1000Km and 1 in 3 die
         • Ash would affect transport, electricity, water and farming
           • Lahars possible
     • International
       • UK would receive ash 5 days later
         • Global climates would change, crops would fail and subsequently many people would die