Fossil Evidence that
illustrates how life forms
evolve
Techniques used to
determine geological time
scales
techniques used to learn
about the earth
Impact of Earthquakes
on the Enviroment
Factors responsible for
Earthquakes
Factors responsible for
mountain building
Factors Responsible for
Ocean Ridges
Factors Responsible for
Volcanic Eruptions
Theory of Plate
Tectonics
Impact of Volcanoes
on The Enviroment
Bibliography
Theory of Plate Tectonics
Plate Tectonics, sometimes called Lithospheric plates,
are large, slabs of oceanic and/or continental crust. Plates come in many sizes.
The largest plates are the Pacific and Antarctic Plate, they measure thousands of
miles across. The Juan de Fuca Plate is off the coast of Washington state, it is a
smaller plate, only a few hundred miles across.
Oceanic plates, are composed of basalt, an iron-rich and heavy rock, that sink deeper
in the mantle. Continental plates, are composed of granite, that is light, that "floats"
and rises above the oceanic plates. Continental plates are usually thicker
(up to 100 km) to balance their height (i.e. mountains). Oceanic plates are usually
very thin (5 km).
Continents may "float" in the middle or off to the side of the plates that they’re on.
The majority of most plates, especially the Pacific Plate, consist of oceanic crust.
