Subduction.

Subduction is a geologic process in which one of the plates in Earth's crust subducts, or slides under, another plate. Subduction is a key part of plate tectonics, which is a scientific theory about how Earth's surface changes. Subduction occurs when one tectonic plate is denser than another. Subduction zones are located in places where two of Earth's plates meet. Scientists believe that subduction is one of the most important forces shaping Earth's crust, and it is responsible for creating mountains, forming volcanoes, and more. Subduction has important effects on all living things on Earth. Although subduction is an important geologic process, the changes it causes occur very slowly.