Here's why:
* Density Difference: Oceanic crust is denser than continental crust. When they collide, the denser oceanic plate is forced to bend and slide beneath the less dense continental plate.
* Volcanism: As the oceanic plate descends, it melts due to friction and heat from the mantle. This molten rock rises to the surface, often creating volcanic arcs along the continental edge.
* Earthquakes: Subduction zones are known for their intense earthquake activity. The movement and friction between the plates create seismic waves that can be very powerful.
While other events like mountain building and trench formation also occur at these boundaries, they are direct consequences of the primary process of subduction.
