DRIVING FORCES OF EARTH'S DYNAMIC CRUST Tectonic plates are massive segments of the Earth's crust that float atop the upper mantle, a layer composed mostly of solid yet deformable rocks. These plates are not stationary, they are in constant motion, driven primarily by convection currents within the Earth's mantle. Convection currents are formed as a result of heat generated from the Earth's core. This heat causes hot, less dense material to rise toward the Earth's surface, while cooler, denser m

The continents and ocean basins are in constant motion due to plate tectonics. This animation shows the plate tectonic evolution of the Earth during the last 540 million years. Modern countries are shown in shads of brown and tan. The age of the ocean floor is show in colors that range from blue (oldest) to red (youngest). The age in millions of years is shown in the upper left-hand corner of the screen. The geologic period is shown in the lower left-hand corner of the screen. Text and animation