plate tectonics

In geology, plate tectonics is a scientific theory that explains the formation of major landforms by the movement of Earth's various “plates” that make up its outermost layer, or crust, along the top of a deeper, molten layer. Tectonic plates include the various oceanic plates as well as the remnants of an ancient supercontinent that broke into pieces and slowly separated, forming the continents that exist today. When the plates collided, they formed mountains, volcanoes, trenches, and fault lines at the points of collision. The geological landscape depends on whether one plate slides under the other (subduction), both plates thrust upward (continental collision), or the plates slide or grind against each other to create transform faults. Plates also form geological features, such as ocean basins, when they move away from each other.