GCSE chemistry unit 1 - plate tectonics

Plate tectonics

The Earth's structure

• The atmosphere - 10km thick (mostly)
• The crust - 5-70km thick)
• The mantle - 3500km thick 
• The core (inner and outer) - 3500km thick

Plate tectonics

1915, Alfred Wegener proposed continental drift. He noted that continents fit together like a jigsaw and found that, where they supposedly met, the rocks and fossils are identical. He could not explain, however, how this happened so his proposal was rejected.

Nowadays we accept the theory because we have found that the plates moved, and continue to move, due to radioactive processes in the core that produce heat which leads to convection currents in the mantle. The convection currents move the plates by about a centimetre a year.

Volcanoes can form where the plates move away from each other or one subsides (goes under the other).

Mountains are formed when plates move towards each other and buckle upwards.

Earthquakes occur when plates slide past each other.

It is difficult to predict exactly when earthquakes and volcanic eruptions will occur.