Tectonics Revision

Tectonics revision

The Earth

• Made up of 4 layers: – – – –

Crust Mantle Outer Core Inner Core

The Crust • Divided up into PLATES – These move very slowly – Move apart = spreading or diverging = constructive – Move together = colliding or converging = destructive – Move sideways past each other = conservative

Constructive Plate margins Usually found under oceans eg: Mid Atlantic Ridge in the Atlantic. Form a spreading ridge. Earthquakes are uncommon. Undersea volcanoes form. Some reach the surface when the sea is shallow. eg. Surtsey & Heimaey of Iceland. • Continents move away from one another. • • • • •

Destructive Plate |Margins • Usually found at the edge of oceans • Feature = deep ocean trenches = Subduction zone e.g. The Kuril Trench off Japan or the Peru Trench off S. America. • Most common around the edge of the Pacific Ocean. • Ocean plate sinks under Continental plate. • Big earthquakes common. • Volcanoes also form in Continental mountain range next to trench. • Fold mountain ranges common eg: Andes, Rockies

Conservative Plate Margins • • • •

Found where two plates move past each other side by side. Can be on ocean/continent boundaries eg: San Andreas Fault Movement infrequent = big pressure build up Site of infrequent very serious earthquakes

Conservative or Transform Margin

The summary