In a surprising discovery, scientists have stumbled upon a smouldering volcano, hiding a kilometre beneath the ice sheet in West Antarctica, which may be building up steam for a massive eruption.
The finding raises concerns about the increased rate of ice loss in the region, researchers said.
In January 2010, a team of scientists set up two crossing lines of seismographs across Marie Byrd Land in West Antarctica.
The goal, said Doug Wiens, professor of Earth and planetary science at Washington University and one of the project’s principle investigators, was essentially to weigh the ice sheet.
Automated-event-detection software was put to work to comb the data for anything unusual.
When the team found two bursts of seismic events between January 2010 and March 2011, Wiens’ PhD student Amanda Lough looked more closely to see what was rattling the continent’s bones.
Uncertain at first, the more Lough and her colleagues looked, the more convinced they became that a new volcano was forming a kilometre beneath the ice.
“I started seeing events that kept occurring at the same location, which was odd. Then I realised they were close to some mountains — but not right on top of them,” Lough said.
The events were weak and of very low frequency, which strongly suggested they weren’t tectonic in origin. While low-magnitude seismic events of tectonic origin typically have frequencies of 10 to 20 cycles per second, this shaking was dominated by frequencies of 2 to 4 cycles per second.
To probe farther, Lough used a global computer model of seismic velocities to “relocate” the hypocentres of the events to account for the known seismic velocities along different paths through the Earth. This procedure collapsed the swarm clusters to a third their original size.
It also showed that almost all of the events had occurred at depths of 25 to 40 kilometres. This is extraordinarily deep — deep enough to be near the boundary between the Earth’s crust and mantle, called the Moho, and more or less rules out a glacial origin.
A colleague suggested that the event waveforms looked like Deep Long Period earthquakes, or DPLs, which occur in volcanic areas, have the same frequency characteristics and are as deep.
“Everything matches up,” Lough said.
The seismologists also talked to Duncan Young and Don Blankenship of the University of Texas who fly airborne radar over Antarctica to produce topographic maps of the bedrock.
“Most mountains in Antarctica are not volcanic, but most in this area are. Is it because East and West Antarctica are slowly rifting apart? We don’t know exactly. But we think there is probably a hot spot in the mantle here producing magma far beneath the surface,” Wiens said.
The discovery of the new as yet unnamed volcano was announced in the journal Nature Geoscience.