What happens at a subduction convergent boundary?

Answer 1

The oceanic crust (the denser crust) is subducted under the lighter crust which basically means that it goes under the upper crust as they meet so they don't crash into each other like at a collision zone.

Answer 2

a subduction zone is a convergent boundary where two tectonic plates collide.

Answer 3

At a subduction zone, a plate forms a trench as it sinks under the other plate. The oceanic crust on the plate sinks back to the mantle at the subduction zone, due to sea-floor spreading.