b'14 Carnegie Science|Summer 2019Diamonds Reveal Key to Earths Stability and HabitabilityT he persistence ofThe images show diamonds from Sierra Leone with sulfur-containing mineral inclusions. Earths continents, despite destructive tectonic activity, has been essential for the emergence of life. This stability depends on how the mantle layerbetween the core and the crustis attached to the landmasses. New researchImages courtesy Gemological Institute of Americaby a group of geoscientists from Carnegie, the Gemological Institute of America, andthe continental crust. The material thatShirey explained. Since this is the only the University of Alberta demonstratescomprises them must thicken, stabilize,tectonically active, rocky planet that we that diamonds can be used to reveal how aand cool under the continent to form aknow, understanding the geology of how our buoyant section of mantle beneath somestrong, buoyant, keel that is fundamentalcontinents formed is a crucial part of of the continents became thick enough tofor preserving the surface landmassdiscerning what makes Earth habitable.provide long-term stability. Science against the relentless destructive forces ofSome scientists think mantle keels formpublished the paper.Earths tectonic activity. But how this isby a process called subduction, when Weve found a way to use traces ofaccomplished has been a matter of debate. oceanic plates sink from the Earths surface sulfur from ancient volcanoes that madeSolving this mystery is key tointo its depths beneath another plate. Others its way into the mantle and eventuallyunderstanding how the continents camethink keels are created by a process in which into diamonds to provide evidence for oneto exist in their current incarnations andplumes of hot magma rise from deep within particular process of continent building,how they survive on an active planet,the Earth.explained lead author Karen Smit of the Gemological Institute of America. Ourvolcanic chaintechnique shows that the geologicmid-ocean ridgeactivity that formed the West Africansubductioncontinent was due to plate tectonic movement of ocean crust sinking into the mantle.Diamonds, beloved by many, are140 km Galso a geologists best friend. BecauseG Dthey originate deep inside the Earth,D LAB cratonupper mantletiny mineral grains trapped inside 410 km upper mantleimpurities to jewelerscan reveal the lithosphericconditions under which it formed.mantletransition zoneIn this way, diamonds act as mineralogical emissaries from the660 km transition zoneEarths depths, explained Carnegie kilometers) beneath the surface,lower mantle lower mantlecoauthor Steve Shirey.About 93 to 124 miles (150 to 200900 kmgeologic formations called mantle keelslike the keel of a boatstabilize kimberlitebasalt/eclogiteThis schematic shows the sections of Earths mantlebetween the crust and core, where diamonds formand subduction, where one plate slips under another into the interior.lithospheric mantleImage courtesy Carnegie Institution for Science/Steve Shirey, adapted from Tappert and Tappert, Rough Diamonds, Cambridge convecting mantle'