Graveyard of Earth’s Plates: Ancient Protocrust of Earth Discovered in Depths of Earth’s MantleEarth's earliest crust, more than four billion years old, survived deep in the mantle / Traces of ancient Earth's crust still exist today in volcanic rocks at Earth's surface / Publication in PNAS Dr. Jonas Tusch and Carsten Münker, both scientists at the Institute of Geology and Mineralogy at the University of Cologne, along with their colleague Dr. Elis Hoffmann, Freie Universität Berlin, used chemical analyses of magmatic rocks to prove that the remains of the first crust of our planet lie buried at great depths in Earth's mantle.