Tectonic Processes.

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Tectonic Processes

Plate tectonic theory

The location of continents today of far removed from what it was millions of years ago, when it is believed that all continents were joined to one land mass. Alfred Wegener put forward a theory regards their movement in 1912 with his theory of Continental Drift. His theory was based on observations such as:

Biological: Coal is found in UK but needs warm, wet, humid conditions to form.

Observational: The shapes of countries appear to 'fit'one another, for example, S.America And Africa.

In the 1940's-1960's the theory was revised and Plate Tectonic theory emerged. It is based on the premise that the lithosphere (crust and rigid upper mantle) is divided into plates, which are moved by convection currents coming from the earth's core.

Plates and Plate Movement

Characteristics of the crust

There are 2 main types of crust that lie on plates and each has its own characteristics:

Oceanic Crust (Sima)

Young (under 200 million years), thin, dense and heavy, will sink. Always being created and destroyed. For example, Basalt.

Continental Crust (Sial)

Old, light, thick (up to 150km under mountains) permanent, does not