Scientists Just Discovered a Molten Layer Below Earth's Surface [View all]

Story by Tim Newcomb • 2h ago



In a new study published in the journal Nature Geoscience, researchers from the University of Texas detected a layer of molten rock hidden under Earth’s tectonic plates, about 100 miles from the surface and exceeding 2,600 degrees Fahrenheit.

In the past, scientists believed molten melt existed in patches, but the new findings reveal the global extent of the molten layer and its relationship to plate tectonics. The layer is part of the asthenosphere, which sits under Earth’s tectonic plates in the upper mantle and gives needed topography, forming a relatively soft boundary that lets plates move through the mantle. Without the softness, Earth’s upper layers would be too rigid for tectonic plate movement.

“When we think about something melting, we intuitively think that the melt must play a big role in the material’s viscosity,” Junlin Hua, research lead from the University of Texas Jackson School of Geoscience, says in a news release. “But what we found is that even where the melt fraction is quite high, its effect on mantle flow is very minor.”

That means the heat and rock in the mantle have the influence on the motion of tectonic plates, giving less prominence to the molten layer. So even though Earth’s interior is largely solid, “over long periods of time, rocks can shift and flow like honey,” Hua says.

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