Final answer:
When plates collide at a convergent boundary, the process known as subduction occurs where one plate moves under another. Subduction zones, which can feature deep ocean trenches and may lead to earthquakes and volcanic activities, are essential in maintaining the Earth's crust balance.
Step-by-step explanation:
When plates collide with one another, it is known as a convergent plate boundary. Within convergent boundaries, a process known as subduction takes place where one plate descends beneath another into Earth's mantle. This occurs because as new crust is created, such as at divergent boundaries, somewhere else on Earth older crust must be destroyed to maintain balance.
Subduction is common at boundaries between oceanic and continental plates or between two oceanic plates. In these zones, the denser oceanic plate is forced beneath the lighter continental plate, or one oceanic plate subducts under the other. The descending plate encounters high pressure and temperature, leading to its melting and eventually to volcanic activity and earthquakes. Subduction zones are typically associated with deep ocean trenches, like the Japan trench, and can create mountain ranges and volcanic arcs. As the process of subduction recycles the Earth's crust, it plays a crucial role in the dynamic evolution of our planet.