The zone, at an angle to the surface of the Earth, down which a lithospheric plate descends. Most present-day subduction zones extend from trenches on the ocean floor, from where a zone of earthquake hypocentres (called a Benioff zone) extends, at an angle ranging from near-horizontal to near-vertical, to a depth of up to 700 km. Andesitic volcanoes form approximately 100 km above the subducting slab, and the presence of andesitic volcanoes in the geologic record is regarded as evidence of an ancient subduction zone and thus of a destructive plate margin.

Subduction zone