These are the locations of the world’s major plate tectonics. A tectonic plate (also called lithospheric plate) is a massive, irregularly shaped slab of solid rock, generally composed of both continental and oceanic lithosphere. Plate size can vary greatly, from a few hundred to thousands of kilometers across; the Pacific and Antarctic Plates are among the largest. Plate thickness also varies greatly, ranging from less than 15 km for young oceanic lithosphere to about 200 km or more for ancient continental lithosphere (for example, the interior parts of North and South America).
The main features of the plate tectonics are:
- The Earth’s surface is made up of a series of large plates (like pieces of a giant jigsaw puzzle).
- These plates are in constant motion travelling at a few centimetres per year.
- The ocean floors are continually moving, spreading from the centre and sinking at the edges.
- Convection currents beneath the plates move the plates in different directions.
- The source of heat driving the convection currents is radioactive decay which is happening deep in the Earth.
- The edges of these plates, where they move against each other, are sites of intense geologic activity, such as earthquakes, volcanoes, and mountain building.
- Plate tectonics is a relatively new theory and it wasn’t until the 1960′s that Geologists, with the help of ocean surveys, began to understand what goes on beneath our feet.