Fossil Record


Fossils have been lost to the fossil record in subduction zones.

Skematic depiction of subductionA 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 Triassic Earththe 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.