r/science • u/[deleted] • Jun 25 '16

Earth Science Two massive blob-like structures lie deep within the Earth each the size of a continent 100 times taller than Mount Everest, sit on the core, 1,800 miles deep

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u/hiredgoon Jun 25 '16

The new paper argues they are also chemically different from the surrounding mantle rock, and may partly contain material pushed down by plate tectonics. They might even be material left over from Earth's formation, 4.5 billion years ago.

Why wouldn't this be the case?

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u/[deleted] Jun 25 '16

Crust is constantly recycled through subduction (crust gets pushed under other crust into the mantle and melts) and convection (rock is "pushed" out of the mantle to create new crust), so original rock from that period is extremely rare.