Plate tentonics

According to the theory of plate tectonics, Earth's crust is composed of a number of individual plates that change shape and position over time. Geophysical evidence indicates that the face of Earth's surface has changed significantly since its initial formation and that the plates on which the continents are located are in constant motion. The movement of the plates is responsible for the formation of ocean basins, mountain ranges, islands, volcanoes, and earthquakes. •Convection currents beneath the plates are responsible for plate movement.http://www.teachersdomain.org/resource/ess05.sci.ess.earthsys.lp_platetectonics/

•The ocean floors are continually moving — spreading from the center, sinking at the edges, and being regenerated.

There are six of majors plates named for the continents embedded within them, such as the North American, African, and Antarctic plates. the minors are no less important when it comes to shaping the Earth. The tiny Juan de Fuca plate is largely responsible for the volcanoes that dot the Pacific Northwest of the United States.

The plates that make up Earth's outter shell are:lithosphere. (This includes the crust and uppermost part of the mantle.)The movement of the plates creates three types of tectonic boundaries: convergent, where plates move into one another; divergent, where plates move apart; and transform, where plates move sideways in relation to each other.

Transform BoundariesThe San Andreas Fault in California is an example of a transform boundary, where two plates grind past each other along what are called strike-slip faults. These boundaries don't produce spectacular features like mountains or oceans, but the halting motion often triggers large earthquakes, such as the 1906 one that devastated San Francisco.

Plates Tentonics