Oceanic crust is denser than continental crust. At a subduction zone, the oceanic crust usually sinks into the mantle beneath lighter continental crust. (Sometimes, oceanic crust may grow so old and that dense that it collapses and spontaneously forms a subduction zone, scientists think.)
The simplest definition of an ecosystem is that it is a community or group of living organisms that live in and interact with each other in a specific environment.
