Friday, November 22, 2013

[Geology • 2013] Seismic Detection of an Active Subglacial Magmatic Complex in Marie Byrd Land, Antarctica | Volcano Discovered Smoldering Under a Kilometer of Ice in West Antarctica


Mount Sidley, the highest volcano in Antarctica, may have a lot of company lurking out of sight. Scientists are using seismographs to hunt for hidden volcanoes in Antarctica.
photo: Doug Wiens

Abstract
Numerous volcanoes exist in Marie Byrd Land, a highland region of West Antarctica. High heat flow through the crust in this region may influence the stability of the West Antarctic Ice Sheet. Volcanic activity progressed from north to south in the Executive Committee mountain range between the Miocene and Holocene epochs, but there has been no evidence for recent magmatic activity. Here we use a recently deployed seismic network to show that in 2010 and 2011, two swarms of seismic activity occurred at 25–40 km depth beneath subglacial topographic and magnetic highs, located 55 km south of the youngest subaerial volcano in the Executive Committee Range. We interpret the swarm events as deep long-period earthquakes based on their unusual frequency content. Such earthquakes occur beneath active volcanoes, are caused by deep magmatic activity and, in some cases, precede eruptions. We also use radar profiles to identify a prominent ash layer in the ice overlying the seismic swarm. Located at 1,400 m depth, the ash layer is about 8,000 years old and was probably sourced from the nearby Mount Waesche volcano. Together, these observations provide strong evidence for ongoing magmatic activity and demonstrate that volcanism continues to migrate southwards along the Executive Committee Range. Eruptions at this site are unlikely to penetrate the 1.2 to 2-km-thick overlying ice, but would generate large volumes of melt water that could significantly affect ice stream flow.


Amanda C. Lough, Douglas A. Wiens, C. Grace Barcheck, Sridhar Anandakrishnan, Richard C. Aster, Donald D. Blankenship, Audrey D. Huerta, Andrew Nyblade, Duncan A. Young, Terry J. Wilson. 2013. Seismic Detection of an Active Subglacial Magmatic Complex in Marie Byrd Land, Antarctica. Nature Geoscience. 2013; DOI: dx.doi.org/10.1038/ngeo1992



Volcano Discovered Smoldering Under a Kilometer of Ice in West Antarctica

: Heat May Increase Rate of Ice Loss

 — It wasn't what they were looking for but that only made the discovery all the more exciting.

In January 2010 a team of scientists had set up two crossing lines of seismographs across Marie Byrd Land in West Antarctica. It was the first time the scientists had deployed many instruments in the interior of the continent that could operate year-round even in the coldest parts of Antarctica.


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