BioEd Online

A remote South Atlantic island, trapped under polar ice, is blowing its top in spectacular fashion. It is the first time that researchers have had a chance to watch an Antarctic lava flow in action.

"I'd give my right arm to be down there now," says John Smellie, a volcano expert at the British Antarctic Survey in Cambridge, UK. "It's very rare that we get to make direct observations of eruptions under ice sheets."

Montagu Island is part of the volcanic South Sandwich Islands, which lie about 2,000 kilometres from mainland Antarctica and are dependent territories of the United Kingdom.

Montagu's active volcano, Mount Belinda, has been grumbling away since late 2001, but for most of that time has produced little more than smoke and ash.

"Then suddenly, towards the end of September, the crater filled with lava and it has been running ever since," says Smellie. "In the past four weeks, it has released half a million cubic metres of lava," he adds. The island, which is about 12 kilometres across, has so far expanded by about 0.2 square kilometres, or roughly 30 football pitches. Meanwhile the melting ice sheet is pouring huge quantities of water into the ocean.

Images of the eruption were snapped by NASA's Earth-monitoring satellite Terra, which passes over the island about twice a day and takes high resolution snaps twice a month. Scientists were alerted to the event by a computerized detection system called MODVOLC. The system was developed at the Hawaii Institute of Geophysics and Planetology in Manoa to churn through Terra's data in search of interesting hot spots.

Hot stuff

Smellie normally studies Antarctic rock formations to find out how eruptions have affected the growth and retreat of ice sheets over the past 30 million years. "But how hot rock interacts with ice is so poorly understood," he says. "This opportunity to monitor a live eruption and see how it affects ice cover is priceless."

Smellie hopes to hitch a ride over the island on a Royal Air Force aeroplane, which will fly from the Falkland Islands next March. "It will be the highlight of my career," he says. Although satellite images are useful, a fly-by will provide a much more accurate picture of the terrain.

The changes to the area will be dramatic. Smellie points out that a relatively small eruption in 1996 beneath the Vatnajökull glacier at Gjálp, Iceland, released a flood that became the second biggest freshwater discharge on the planet at the time, beaten only by the River Amazon, he says.

When lava hits ice and snow, it can also create dangerous volcanic mud flows, says Matt Patrick, part of the Hawaii team that got the first glimpse of the satellite images. "These data should help with our understanding of these processes in general," he adds. Details of the eruption are presented in the latest issue of the Bulletin of Volcanology¹.