Wednesday, December 11, 2013

Giant Blob of Hot Rock Hidden Under Antarctic Ice

Many researchers have long suspected that Marie Byrd Land sits atop a hotspot, because the region swells above the surrounding topography like the top of a warm soufflé (and it has lots of volcanoes). But with few seismometers sitting on the ice, scientists were left speculating about what lies beneath Antarctica's ice.
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The evidence for the new hot zone, called a thermal anomaly, comes from a massive, temporary earthquake-monitoring network called Polenet that was installed between 2010 and 2012, giving scientists an unprecedented look at Antarctica's crust and mantle. (A gravity survey conducted at the same time also suggests there is a big warm spot beneath this part of West Antarctica.)
But confirming that Marie Byrd Land is truly above a hotspot may require a return trip to Antarctica for another seismic experiment, said Doug Wiens, principal investigator on Polenet.
"What's absolutely sure is there's a big thermal anomaly, a big blob," said Wiens, a seismologist at Washington University. "What's less sure is whether that anomaly goes deeper."
The thermal anomaly extends 125 miles (200 kilometers) below Marie Byrd Land, Lloyd said. Below about 255 miles (410 km), where a mantle plume's trailing tail would also leave a hotter-than-average mark in mantle rocks, there's little evidence for a rising hotspot, said Erica Emry, a postdoctoral researcher at Pennsylvania State University

.http://www.weather.com/news/science/giant-blob-hot-rock-hidden-under-antarctic-ice-20131211
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