At deep-sea trenches
, the ocean crust plunged deep into the Earth's mantle triggering major earthquakes.
These plates converge at deep-sea trenches
, plate boundaries where one plate sinks (subducts) below the other at so-called subduction zones.
Scientists today recognize distinct assemblages of animal species in six major seafloor regions (colored dots) along the system of volcanic mountains and deep-sea trenches
that form the borders of Earth's tectonic plates.
, which are subject to frequent catastrophic sediment slumping, have relatively low diversities.
(See Oceanus Winter 1992/93 for a discussion of "Island Arcs, Deep-Sea Trenches
, and Back-Arc Basins.) Ocean drilling has provided fundamental information about colliding-plate processes, including accretion of sediments and volcanic edifices from underthrusting to overriding plates, emplacement of rocks that have been altered by the forces at work in colliding-plate zones, and the nature of continental collisions.