Saturday, January 26, 2008

Antartica is spread out over an active volcano

A team of British researchers has uncovered the first evidence of a volcanic eruption beneath the West Antarctic ice sheet.

The researchers from the British Antarctic Survey, in findings published in the February edition of the journal Nature Geosciences, report the Hudson Mountains subglacial volcano erupted about 2,200 years ago.

"We believe this was the biggest eruption in Antarctica during the last 10,000 years," said lead author Hugh Corr in a release. "It blew a substantial hole in the ice sheet and generated a plume of ash and gas that rose around 12 km into air."

This ash and gas eventually fell back to the ice surface and was buried by years of snow, the team reports, creating a bright reflection in the ice over an elliptical area of about 23,000 km square.
Previous studies had misidentified the reflective area as the ice bottom. The researchers discovered this ash layer by analyzing radar data collected during an airborne survey of the area in 2004-05.

Additionally, ice cores extracted from the area showed a thin layer of ice that conducts electricity unusually well. The team said this conductivity may be a result from the volcano blasting acid and other conductive chemicals into the air that subsequently fell to the ground and became incorporated into the ice.

The thickness of the ice above the ash layer suggests the eruption occurred 2,200 years ago, most likely around 325 BC, the report said.

The researchers have no direct evidence of recent eruptive activity, but believe the volcano is still active. Evidence of recent activity includes a report of steam in the area in 1974 and an eruption reportedly seen in satellite data in 1985.

An active volcano in the area could generate heat under the ice and accelerate the melting of the nearby Pine Island glacier, the report said. As well, the heat would create melt-water to lubricate the glacier's movement.

"The flow of this glacier towards the coast has speeded up in recent decades and it may be possible that heat from the volcano has caused some of that acceleration," said Prof. David Vaughan, another study author, in a release.

However, he adds, the heat from the Hudson Mountains subglacial volcano would probably not affect neighbouring glaciers.

"It cannot explain the more widespread thinning of West Antarctic glaciers that together are contributing nearly 0.2 mm per year to sea-level rise," Vaughan said. "This wider change most probably has its origin in warming ocean waters."

The team said the finding may help researchers refine their predictions on rising sea levels and the future of the ice sheet.

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