Volcano Activity - Antarctica, Marie Byrd Land, [Mount Sidley Volcano]

Earth Watch Report  -  Volcanic Activity

Image Source   :  Wikimedia Commons
Marie Byrd Land, West Antarctica
Author NASA/Michael Studinger

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Volcano Activity

Antarctica

Marie Byrd Land, [Mount Sidley Volcano]

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Volcano Activity in Antarctica on Wednesday, 11 December, 2013 at 04:25 (04:25 AM) UTC.

Description

A big, hot blob hiding beneath the bottom of the world could be evidence of a long-sought mantle plume under West Antarctica, researchers say. The possible hotspot �" a plume of superheated rock rising from Earth's mantle �" sits under Marie Byrd Land, a broad dome at West Antarctica's edge where many active volcanoes above and below the ice spit lava and ash. The hot zone was discovered with seismic imaging techniques that rely on earthquake waves to build pictures of Earth's inner layers, similar to how a CT scan works. Beneath Marie Byrd Land, earthquake waves slow down, suggesting the mantle here is warmer than surrounding rocks. The strongest low-velocity zone sits below Marie Byrd Land's Executive Committee Range, directly under the Mount Sidley volcano, said Andrew Lloyd, a graduate student at Washington University in St. Louis. "The slow velocities suggest that it's a mantle hotspot," Lloyd said on Monday during the fall meeting of the American Geophysical Union. The hot zone also matches up with Marie Byrd Land's high topography and active volcanoes, Lloyd said. 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. 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. "There's no smoking gun," Emry said. However, more work remains to be done on the Polenet data, which could reveal new clues and further refine what the mantle looks like under West Antarctica, Emry told LiveScience's OurAmazingPlanet.

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