Pieces of crust and brittle uppermost mantle, perhaps 100 kilometers thick and hundreds or thousands of kilometers wide, that cover the Earth's surface. The plates move very slowly over, or possibly with, a viscous layer in the mantle at rates of a few centimeters per year. (See Figure 8. )

See tectonic plates.

The surface of the Earth is broken into large plates that move very gradually over time. Where the edges of two plates come together, there is often intense and sometimes dangerous geological activity, involving earthquakes and volcanoes. The massive pressure that results from plate movements can build mountain ranges, which continue to push upwards for many years, as plates buckle against each other.

Thick, moving slabs of rock composed of crust and the uppermost layer of the under lying mantle.

Rigid slabs that make up the Earth's crust; see "plate tectonics"

The rigid pieces that make up the puzzle of Earth's crust.

The outer shell of the Earth is made up of almost rigid plates that fit together. These plates "float" on a dense, more fluid layer just beneath them. The plates slowly move around, though we do not notice it in our everyday lives. Earthquakes occur most frequently on, or near, the edges of plates where stress is most concentrated.

The crust of the Earth is broken into plates. The plates are enormous chunks of rock that float atop the soft mantle. The plates are moving at a speed that has been estimated at 1 to 10 cm per year. Oceanic plates (those that are under the ocean) are thinner and denser than continental plates. Forward Backward

Large sections of Earth's lithosphere that are separated by deep fault zones.

Huge, mobile rock slabs of varying sizes and thicknesses that form the earth's crust.

Giant, rigid slabs of the Earth's crust. The plates "float" on a dense, fluid layer just beneath them.

giant slabs of underground rocks, often bigger than continents

Tectonics The term used to describe the process which results in the movement of the earths crust. Over time the semi-molten mantle within the earth creates convection currents, which cause heated rock to rise and cooling rock to descend. At the earths surface this process results in the movement of the continental plates. The resulting movement means that the UK and US are moving apart at roughly the same rate that an average persons finger nails grow.