hypothetical movement of earth's crust plates: a theory that ascribes continental drift, volcanic and seismic activity, and the formation of mountain belts to moving plates of the Earth's crust supported on less rigid mantle rocks

geology See also plate tectonics the theory that the earth's continents move gradually over the surface of the planet on a substratum of magma. The present-day configuration of the continents is thought to be the result of the fragmentation of a single landmass, Pangaea, that existed 200 million years ago

The process by which new material that lies under the ocean rises and pushes the existing tectonic plates aside, creating new crust as it does so.

A series of mountain ranges on the ocean floor, more than 84,000 kilometers (52,000 miles) in length, extending through the North and South Atlantic, the Indian Ocean, and the South Pacific. According to the plate tectonics theory, volcanic rock is added to the sea floor as the mid-ocean ridge spreads apart.

(across the back of various types of cheque card, credit card, etc) a dark stripe of magnetic material consisting of several tracks onto which information may be coded and which may be read or written to electronically

The theory of plate tectonics refers to the science that suggests that the outer rigid layer of the earth is divided into plates that move relative to each other across the surface of the earth. It encompasses the study of plates, plate boundaries and the effects of the movement of these plates. Plate movement is often too slow to be measured.

the transfer of heat by the mass movement of heated particles into an area of cooler fluid

1. (of two or more lines, paths, etc) moving towards or meeting at some common point

diverging; differing; deviating

to change in form, appearance, or structure; metamorphose.

an act or instance of subducting; subtraction or withdrawal.

the solid portion of the earth (distinguished from atmosphere, hydrosphere ).

The asthenosphere lies beneath the lithosphere and consists of partially molten rock.

in geology, the innermost part of a core, specif. a solid sphere in the middle of the fluid core such as the iron-nickel core of the Earth

The outer core is located about 1800 milesbeneath the crust and is about 1400 miles thick.

Geology . the portion of the earth, about 1800 miles (2900 km) thick, between the crust and the core. Compare core1 ( def 10 ) , crust ( def 6 ) .