Plate Tectonics

Plate Tectonics

1. Structure of the Earth

   • Core - Iron, Nickle, semi-molten outer core, 6,000C
   • Mantle - iron, magnesium, semi-molten, 5,000C
   • Asthenosphere - molten, convection currents occur
   • Crust - coolest, less dense rocks
     • Oceanic - basaltic, 6-10km thick
       • Continental - can be up to 70km, made from various rocks
   • Lithosphere - contains the rigid part of the mantle and the crust, 80-80km

2. Pangaea

   • Alfred Wegener published an idea that a supercontinent called Pangaea lived 300 million years ago
   • Split into two continents - Laurasia in the south and Gondwanaland in the north.
   • Evidence
     • Geological - the fitting of south America and Africa, evidence of glaciation in India, Antarctica and south America., rock sequences in Scotland and Canada.
     • Biological - fossil remains of Mesosaurus found in both southern America and southern Africa., plant remains in India and Antarctica
   • Palaeomagneticism - lava erupts from the Mid Atlantic Ridge, minerals in the lava are aligned with the Earth's magnetic pull. Sea floor spreading; older bands of rock are further away from the ridge.. The subduction zones equal out this increase in landmass.

3. Types of plate margins

   • Destructive
     • Subduction Zone
     • Less dense plate, subducts
       • Oceanic<Continental
     • Earthquakes and volcanoes
   • Constructive
     • Two plates pulling apart
     • Lava rises from the ridge and creates new land
   • Conservative
     • Two plates slide past each other
     • Friction is created, release causes earthquakes
     • San Andreas Fault line

4. Tectonic Plate Landforms

   • Constructive
     • Oceanic Ridge - where two plates pull apart there is a weaker zone in the crust and an increase in heat near the surface. the hotter expanded crust forms a ridge.
       • Iceland - Mid Atlantic Ridge
     • Rift Valley - the land mass fractures due to heat and rifts appart, central parts of land drop and form rift valleys.
   • Destructive
     • Fold mountains - during subduction, one plate is melted and increased pressure then leads to volcanoes forming. Once the chamber is empty. The volcano becomes inactive and thus becomes a mountain.
     • Island Arcs - a string of volcanic islands in the ocean along the plate boudary.

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