subduction zone is an area on Earth where two tectonic
plates meet and move towards one another, with one sliding
underneath the other and moving down into the earth's
mantle. Such continental collisions proceed at a speed
of only several inches per year. Typically, an oceanic
plate slides underneath a continental plate, and this
often creates a zone with many volcanoes and earthquakes.
The process of subduction can and has removed vast
swaths of fossils from the
fossil record. A good example is found in the Triassic
fossil record. Earth during the Triassic had all its
land mass in a single supercontinent, Pangaea, centered
near the equator. All the deep-sea sediments deposited
during the Triassic have been subsumed into the earth’s
mantle through subduction of oceanic plates, leaving
no deep ocean fossil record from the period. The supercontinent
Pangaea was rifting during the late Triassic, and
eventually separated into areas that are now New Jersey
and Morocco. Because a single landmass has a shorter
periphery than multiple continents of the same area,
marine deposits across the planet are relatively uncommon.
Consequently, the North American marine fossils come
from but a few western exposures.