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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,
by mirimir 8y ago
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.
- teilo 8y agoDashing my hopes for a journey to the center of the earth.
- hnthroaway1926 8y agomaybe we just need to dig shallow tunnels and wait a few million years for them to be pulled under
- hammock 8y agoA 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.
- mirimir 8y agoAs 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.