What does subduction refer to in tectonic processes?

Subduction refers to the process in tectonic activity where one tectonic plate moves under another and is forced into the mantle due to gravitational forces. This often occurs at convergent plate boundaries, where an oceanic plate collides with a continental plate or another oceanic plate, resulting in the denser oceanic plate sliding beneath the less dense continental or another oceanic plate.

This process is significant because it is responsible for many geological phenomena, such as the formation of deep ocean trenches, volcanic arcs, and earthquake activity. For example, the Pacific Plate is subducting beneath the North American Plate, leading to the creation of the Cascade Range, which includes several volcanoes.

The other choices describe different tectonic processes. Movement apart describes divergent boundaries, where plates pull away from each other, leading to seafloor spreading. Colliding continental plates are referred to as continental collision rather than subduction because it often leads to mountain building instead of one plate sinking beneath the other. Lastly, the formation of mid-ocean ridges occurs at divergent boundaries where two tectonic plates pull apart, allowing magma to rise and create new seafloor.