Earth Structure and Theory of Plate Tectonics

Hazards

Lithosphere

• Crust

• Solid, rigid, upper section of the mantle

• 80-90cm thick

Asthenosphere

• Lies beneath the lithosphere

• Semi-molten on which the plates will float on and move

Continental Drift

• Alfred Wegener

• 1912

• Started with a ‘super continent’ called Pangaea

• Split apart (Triassic, 200 million years ago) into 2 masses

  • Laurasia in the north

  • Gondwanaland in the south

Evidence for Continental Drift

• Puzzle-like fit of South America and West Africa

• Fossil brachiopods found in Indian limestone are comparable with similar fossils in Australia

• Fossil remains of the reptile Mesosaurus are found in both South America and Southern Africa. Unlikely it migrated

• Rocks in Brazil and West Africa have similar striation

• The fossilied remains of a plant which ezisted when coal was being formed have been located only in India and Antarctica

• Rock sequences in Northen Scotland closely agree with those founf in Eastern Canada