What happens at a subduction zone?

At a subduction zone, one tectonic plate is forced beneath another plate. This process occurs when two plates converge, and the denser oceanic plate is typically subducted under a less dense continental plate. As the subducted plate moves deeper into the mantle, it leads to various geological phenomena, including the formation of deep ocean trenches, volcanic activity, and seismic events such as earthquakes.

In contrast to the other options, at divergent boundaries, two plates move apart from each other, creating new crust as magma rises to the surface. The option involving the sliding of plates past one another refers to transform boundaries, where plates slide horizontally against one another without significant upward or downward movement. Lastly, when two plates collide and form new crust, this describes a convergent boundary where both plates are of similar density, which may lead to mountain-building rather than subduction. Therefore, the correct action at a subduction zone is the downward movement of one plate beneath another, highlighting the dynamic processes at tectonic boundaries.