When two tectonic plates collide, the oceanic crust, which is denser and thinner than continental crust, usually subducts beneath the other plate. This process is called subduction. Specifically:
- If an oceanic plate collides with a continental plate, the denser oceanic crust bends and is pulled beneath the lighter, thicker continental crust.
- If two oceanic plates collide, the older, cooler, and therefore denser oceanic plate subducts beneath the younger, less dense oceanic plate.
- Subduction zones form at these collision sites, often creating deep oceanic trenches.
- As the oceanic crust sinks into the mantle, it heats up and releases water and gases, which cause the overlying mantle to melt and form magma. This magma can rise to create volcanic arcs, either as volcanic mountain chains on continents or as chains of volcanic islands in the ocean.
- Subduction also leads to powerful earthquakes and can trigger tsunamis.
Thus, the typical behavior of oceanic crust during tectonic plate collision is to sink beneath the other plate through subduction, forming trenches and volcanoes as a result of this process.
