It's a song of fire and ice — an active volcano that's spewing magma at a depth of more than a half-mile beneath a massive sheet of ice. It's an unprecedented discovery that hints at the possibility for a huge eruption, but with completely unpredictable consequences.
A team of seismologists led by Douglas Wiens of Washington University made the discovery after detecting a series of low-magnitude earthquakes in Marie Byrd Land in western Antarctica — the kind of tremors that often precede volcanic eruptions. The researchers ruled out the possibility that these events, which were happening at a depth of 15 to 25 miles (25 to 40 km) beneath the sub-glacial surface, were caused by ice quakes, glacial motion, or tectonic activity owing to their deep, long-period waves. And because these tremors were happening close to the boundary between the Earth's crust and mantle, it further raised the intriguing possibility that it was related to volcanic activity.
The discovery of the volcano, which rests about a half-mile (1,000 m) beneath the ice, has reinforced long-held suspicions that volcanic activity resides along the sizeable West Antarctic Ice Sheet. The region features several volcanoes along the coast and offshore, but this is the first time scientists have confirmed magma action so far inland.
So what happens when a volcano erupts so far under the ice? The scientists speculate that underground magma and fluids force open new paths and fracture rock (which causes the seismic activity). If the volcano were to experience a serious eruption, it would likely melt the bottom of the ice sheet immediately above the vent. But what would happen next is anybody's guess.
Interestingly, Iceland sometimes experiences massive floods called jökulhlaups. This happens when volcanic eruptions melt glaciers, resulting in a tremendous release of melt water.
But it's fairly obvious that, in the case of the Antarctic volcano and the half-mile sheet of ice above it, it would have to take a tremendous explosion to budge or melt it — something akin to a Yellowstone caldera event. If this were to happen, it could result in rapid ice melt and a dramatic rise of sea levels.
That said, even a small eruption could have noticeable effects.
"If you have a future eruption it's going to increase the heat flow, so you're going to have more melting in the surrounding area, which will then lead to more water at the base of the ice sheet and cause the overlying ice flow to increase in velocity because it's been lubricated," noted study coauthor Amanda Lough, a seismology graduate student at Washington University in St. Louis.
Radar imaging also revealed a buried layer of ash caused by an eruption of Mt. Waesche about 8,000 years ago, and evidence of small flows of magma on the sub-ice topography.
Read the entire study at Nature Geoscience: "Seismic detection of an active subglacial magmatic complex in Marie Byrd Land, Antarctica."