Rock that sank over 90 kilometres into Earth reveals a sharp shift in thermal gradient

A rock found on Goodenough Island indicates an unexpected thermal gradient change during its descent deep within Earth's crust. Researchers estimated that this rock traveled over 90 kilometres into a subduction zone about 4.4 million years ago. Initial warm conditions shifted to a cold thermal regime as it descended further into the Earth. Both shearing stress and the youth of the subduction zone may explain this temperature change.

from Science News: Fresh Discoveries, Research & Breakthroughs https://ift.tt/Yi70gbB
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