Tectonic Plates

Tectonic Plates

1. Earth's surface

   • Centre of the Earth is a ball of solid iron and nickel called the core
     • Around the core is the mantle, which is semi-molten rock that moves very slowly
       • The outer layer of the Earth is the crust. About 20km thin
         • Continental
           • Less dense
           • Thicker
         • Oceanic
           • More dense
           • Thinner
   • Plates move because the rock in the mantle underneath is moving
   • Where plates meet are called boundries or plate margins

2. Plate margins

   • Destructive
     • Two plates moving towards each other
       • Eg. along the coast of Japan
     • Where an oceanic plate meets a continental plate, the denser oceanic plate is forced down into the mantle and destroyed
       • Often creates volcanoes and ocean trenches
     • Where two continental plates meet, the plates smash together but no crust is destroyed
   • Constructive
     • Where two plates are moving away from each other
       • Eg. at the mid-Atlantic ridge
     • Magma rises from the mantle to fill the gap and cools, creating new crust
   • Conservative
     • Two plates moving sideways past each other or moving in the same direction but as different speeds
       • E.g. along the west coast of the USA
     • Crust isn't created or destroyed