When continental and oceanic crusts collide, the result is usually a subduction zone. In this process, the oceanic crust, being denser, gets forced beneath the continental crust. As the oceanic plate moves beneath the continental plate, it sinks into the Earth's mantle. This process leads to the formation of a deep ocean trench at the collision boundary, and the subducting oceanic plate also releases water vapor and carbon dioxide into the overlying mantle, potentially leading to volcanic activity and the formation of mountain ranges in the continental crust above the subduction zone.