Rugged 'mountains' taller than Everest lurk deep inside Earth

nationalgeographic.com

85 points·pseudolus··7 comments

Oh, 450 miles down.

I first thought they were talking about some place like LA, which is flat with occasional rock outcroppings. That's a mountain range that silted up.

tl;dr Some areas of the boundary between the upper and lower mantle are littered with huge (~10 km scale) fragments of subducted crust.

Edit: I recall reading, some years ago, that oceanic crust sometimes fragments during subduction. Using seismic tomography, one can sometimes see pieces that have separated from subducting slabs. Otherwise, the slab just becomes less well defined with increasing depth.

Dashing my hopes for a journey to the center of the earth.

maybe we just need to dig shallow tunnels and wait a few million years for them to be pulled under

A subducted crust would be like a reverse or upside down mountain, right? Is it accurate to call them mountains.

Like the difference between chutes and ladders.

As I understand it, these crust fragments wouldn't just be lying flat on the boundary between the lower and upper mantle. They would likely have rotated during their movement in the flowing upper mantle, and gotten stuck at the boundary in some ~random orientation.

As an analogy, consider some layered drink. Say peppermint schnapps over creme de cacao. Then add some chunks of dark chocolate. I'm guessing that they'd settle out at the interface, being denser than the peppermint schnapps, but less dense than the creme de cacao.

National Geographic hosts one of the most superfluously code-encrufted websites on earth, thus it's unintentionally fitting that their article on subterranean topography references a subject abysmal.

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