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"We've found a way to use traces of sulfur from ancient volcanoes that made its way into the mantle and eventually into diamonds to provide evidence for one particular process of continent building," explained Karen Smit of the Gemological Institute of America, lead author on the group's paper, which appears this week in Science. "Our technique shows that the geologic activity that formed the West African continent was due to plate tectonic movement of ocean crust sinking into the mantle."
Diamonds may be beloved by jewelry collectors, but they are truly a geologist's best friend. Because they originate deep inside the Earth, tiny mineral grains trapped inside of a diamond, often considered undesirable in the gem trade, can reveal details about the conditions under which it formed.
Way - Act - Emissaries - Earth - Depths
"In this way, diamonds act as mineralogical emissaries from the Earth's depths," explained Carnegie co-author Steve Shirey.
About 150 to 200 kilometers, 93 to 124 miles, beneath the surface, geologic formations called mantle keels act as stabilizers for the continental crust. The material that comprises them must thicken, stabilize, and cool under the continent to form a strong, buoyant, keel that is fundamental for preserving the surface landmass against the relentless destructive forces of Earth's tectonic activity. But how this is accomplished has been a matter of debate in the scientific community.
Mystery - Continents - Incarnations - Planet - Shirey
"Solving this mystery is key to understanding how the continents came to exist in their current incarnations and how they survive on an active planet," Shirey explained. "Since this is the only tectonically active, rocky planet that we know, understanding the geology of how our continents formed is a crucial part of discerning what makes Earth habitable."
Some scientists think mantle keels form by a process called subduction, by which oceanic plates sink from the Earth's surface into its depths when one tectonic plate slides beneath...
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