India’s missing mass has likely been mixed back into the Earth’s mantle
The Himalayan mountains don’t often get compared to pool floats, but then again hunks of India and Eurasia don’t often go missing either. Both concepts play a role in a recent study of how India is slowly slamming into Asia, and shrinking in the process. While the world’s highest mountains are evidence of tectonic plates pushing material upwards, they don’t seem to account for all the material that should be there. Nobody thinks this land disappeared entirely, but even being pushed deeper underground isn’t really supposed to happen.
The key components of this model are the Earth’s crust and mantel. The crust is all the rock and dirt we normally think of as “earth.” The mantel is a deeper, denser layer of rocky silicate, but on a geological timescale it acts like a viscous fluid. The assumption has long been that material from the crust would not really enter the mantle due to their relative densities. If something from the crust was pushed down to the mantle, it should immediately surface again, like a pool float that’s released underwater, quickly rising to the surface. However, after eliminating other possibilities for India’s missing mass, researchers from the University of Chicago are suggesting that things may not be that simple.
Explaining itinerant elements
In a study encompassing a variety of data sets about the Indian and Eurasian tectonic plates, the missing crust seems to have ignored our existing models and become enveloped in the Earth’s mantle. This could then explain where the missing mass went, as well as an unrelated puzzle concerning volcanoes. Lead and uranium are generally found in the Earth’s crust, not the mantel, but somehow both elements turn up in eruptions pumping magma from deeper under the ground. If the mantle does absorb components of the Earth’s crust, it could help make sense of where the lead and uranium are coming from.
Source: How Did a Chunk of India and Eurasia Just Disappear? by Stephanie Pappas, Live Science