A unique rock formation in China holds clues that tectonic plates subducted, or went underneath other plates, during the Archean eon (4 billion to 2.5 billion years ago), just as they do nowadays, a new study finds. 

This 2.5 billion-year-old rock, known as eclogite, is rare, forming when oceanic crust is pushed deep into the mantle (the layer between the crust and the core) at relatively low temperatures. This type of high-pressure, low-temperature rock is “largely confined to subduction zones on the present Earth,” study co-lead researchers Timothy Kusky and Lu Wang, Earth scientists at the China University of Geosciences, told Live Science in an email.


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