Plate Tectonics and Continental Drift

Plate Tectonics and Continental Drift


The Plate Tectonic Theory

* The earth's crust is divided into separate parts called tectonic plates.
* These plates float on the partially molten rocks of the upper mantle.
* The plates move due to convection cells in the mantle.
* Margins are the areas between the tectonic plates. Margins of converging plates are called constructive margins while margins of diverging plates are called constructive margins. Margins where the plates slide against each other are called conservative margins.
* Plates can be oceanic or continental. When an oceanic plate meets a continental plate, it's drawn beneath the margin of the continental plate and the rocks of the oceanic plate go into the mantle. When a continental plate meets another continental plate, folding may occur and fold mountains created.
The History of Continental Drift
* Continents drift due to the movement of the tectonic plates.
* Originally, there was one large continent called Pangea surrounded by a sea called Panthalassa. It is believed Pangea was centered around present day Africa.
* Pangea split into two other continents. The northern continent was Laurasia and the southern continent Gondwanaland. Between the two wad a sea called Tethys.
* Gondwanaland then split into the present continents.