The First Solid Evidence of Eruptions Under Antarctic Ice

The First Solid Evidence of Eruptions Under Antarctic Ice
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In August, researchers at Edinburgh University announced that frigid West Antarctica is home to at least 138 volcanoes, all concealed within an ice sheet that's up to two kilometers thick in some places!

The finding left Robert Bingham, one of the study's authors, with an urgent question.

“The big question is: how active are these volcanoes? That is something we need to determine as quickly as possible," he told The Guardian.

“If one of these volcanoes were to erupt it could further destabilise west Antarctica’s ice sheets. Anything that causes the melting of ice – which an eruption certainly would – is likely to speed up the flow of ice into the sea."

Luckily, Bingham didn't need to wait long for an answer. A team of scientists from New Mexico Tech, Dartmouth College, and Vermont Technical College has uncovered evidence of volcanic eruptions in ice cores taken from the West Antarctic ice sheet (WAIS). A paper describing their findings has just been published in Scientific Reports.

Nels Iverson, a PhD Candidate in Geochemistry, and his team examined an ice core situated near two known volcanoes in the ice sheet, Mount Thiel and Mount Resnick. Utilizing scanning electron microscopy and electron microprobe analysis, they found thick layers in the ice core dating back 22.3 thousand years and 44.8 thousand years. These layers were filled with tephra, rock fragments and particles ejected by volcanic eruptions (see figure below).

The researchers think the two eruptions that deposited the tephra were fairly small, with occasional explosions when glacial meltwater interacted with red hot magma. They would have certainly breached the surface of the ice sheet, however.

The findings show that at least some of the volcanoes below the West Antarctic ice sheet are not extinct, with the most recent eruption occurring roughly 22,300 years ago.

The researchers worry that the current trend of ice loss could awake Antarctica's volcanoes from their dormant slumber.

"Continuing ice loss from WAIS will eventually lower the ice sheet elevation and may cause a positive feedback by increasing volcanism in West Antarctic. Although there is no supporting evidence linking enhanced volcanism with collapse of WAIS in the Quaternary, increased volcanism could produce more basal melt water, increasing ice flow and ice loss thus perpetuating positive feedback. The delicate balance between deglaciation and volcanism may have a profound effect on the stability of WAIS and the subsequent sea level rise."

Source: Nels A. Iverson, Ross Lieb-Lappen, Nelia W. Dunbar, Rachel Obbard, Ellen Kim & Ellyn Golden. The first physical evidence of subglacial volcanism under the West Antarctic Ice Sheet. Scientific Reports 7, Article number: 11457 (2017) doi:10.1038/s41598-017-11515-3

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