Seismometers Deployed Across West Antarctic Rift System and Marie Byrd Land Show Mantle Plume, Other Geological Intrigues

Planetary scientists would be thrilled if they could peel the Earth like an orange and look at what lies beneath the thin crust. We live on the planet's cold surface, but the Earth is a solid body and the surface is continually deformed, split, wrinkled and ruptured by the roiling of warmer layers beneath it.

The contrast between the surface and the depth is nowhere starker -- or more important -- than in Antarctica. What is causing the mysterious line of volcanoes that emerge from the ice sheet there, and what does it mean for the future of the ice?

"Our understanding of what's going on is really hampered because we can't see the geology," said Andrew Lloyd, a graduate student in earth and planetary sciences in Arts & Sciences at Washington University in St. Louis. "We have to turn to geophysical methods, such as seismology, to learn more," he said.

Lloyd helped deploy research seismometers across the West Antarctic Rift System and Marie Byrd Land in the austral summer of 2009-10. He then returned in late 2011 and snowmobiled more than 1,000 miles, living in a Scott tent, to recover the precious data.

The recordings the instruments made of the reverberations of distant earthquakes from January 2010 to January 2012 were used to create maps of seismic velocities beneath the rift valley. An analysis of the maps was published online in the Journal of Geophysical Research: Solid Earth on Nov. 12, 2015 (doi:10.1002/2015JB012455).

This is the first time seismologists have been able to deploy instruments rugged enough to survive a winter in this part of the frozen continent, and so this is the first detailed look at the Earth beneath this region.

Not surprisingly, the maps show a giant blob of superheated rock about 60 miles beneath Mount Sidley, the last of a chain of volcanic mountains in Marie Byrd Land at one end of the transect. More surprisingly, they reveal hot rock beneath the Bentley Subglacial Trench, a deep basin at the other end of the transect.

The Bentley Subglacial Trench is part of the West Antarctic Rift System and hot rock beneath the region indicates that this part of the rift system was active quite recently.

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