4um: Volcanic eruptions reshape Arctic ocean floor: study

The Arctic seabed is as explosive geologically as it is politically judging by the "fountains" of gas and molten lava that have been blasting out of underwater volcanoes near the North Pole.

"Explosive volatile discharge has clearly been a widespread, and ongoing, process," according to an international team that sent unmanned probes to the strange fiery world beneath the Arctic ice.

They returned with images and data showing that red-hot magma has been rising from deep inside the earth and blown the tops off dozens of submarine volcanoes, four kilometres below the ice. "Jets or fountains of material were probably blasted one, maybe even two, kilometres up into the water," says geophysicist Robert Sohn of the Woods Hole Oceanographic Institution, who led the expedition.

Chunks of broken sea floor rock, or "talus ejecta" and large-grain pyroclastic deposits cover an outer slope of the Oden volcano on the seabed floor near the North Pole.

He and his colleagues, who describe the underwater scene in the journal Nature today, estimate that exploding mixtures of lava and gas flew out of the volcanoes at speeds of more than 500 metres a second. When the material hit the frigid seawater, Sohn says it would have formed huge clouds that rained volcanic material down on the sea floor, creating the carpet of glassy shards and bits that can be seen for kilometres.

The team explored the volcanoes last summer as the Russians were planting a flag on the nearby sea floor triggering an international flap over ownership of the seabed.

Sohn said in an interview Wednesday that his crew of 30 researchers from the U.S., Europe and Japan chuckled over the "grandstanding" as the Russians rumbled by in their icebreakers. But they stayed focused on the intriguing spot on the Gakkel Ridge they had come to explore. The 1,800-kilometre-long ridge, which cuts across the Arctic from Greenland to Siberia, is in international waters. It is one of the planet's "spreading" ridges where molten rock rises up from inside the earth creating new crust.

The $5-million expedition was financed by the U.S. National Science Foundation and NASA, which hopes to use the know-how gained in its hunt for extraterrestrial life. The scientists sent three unmanned probes down through the ice to explore a 30-kilometre-long stretch of the ridge where a swarm of undersea earthquakes occurred in 1999.

The probes, one of which "flew" just two to five metres above the sea floor, gathered samples and images that point to remarkable under sea eruptions. In the valley where the two crustal plates are coming apart, which is about 12 kilometres across, they found dozens of distinctive flat-topped volcanoes that appear to have erupted in 1999, producing the layer of dark, smoky volcanic glass on the seabed.

"The scale and magnitude of the explosive activity that we're seeing here dwarfs anything we've seen on other mid-ocean ridges," says Sohn, who studies ridges around the world. The volume of gas and lava that appears to have blasted out of the Gakkel volcanoes is "much, much higher" than that seen at other ridges.

Sohn says it would have been "spectacular to witness" the eruptions, but he says it is a good thing there is four kilometres of seawater on top of the Gakkel Ridge as the eruptions would have been "highly problematic" had they occurred on dry land.

The scientists say the heat released by the explosions is not contributing to the melting of the Arctic ice, but Sohn says the huge volumes of CO2 gas that belched out of the undersea volcanoes likely contributed to rising concentrations of greenhouse gases in the atmosphere. How much, he couldn't say.

There are no volcanoes exploding in the area right now, but they scientists say there appears to still be a lot happening on the sea floor. "I had the impression this whole central volcano area was oozing warm fluid," says Henrietta Edmonds of the University of Texas, who was on the expedition tracking the plumes of warm waters rising from the spreading ridge. She says they point to the presence of "gushing black smokers" as well as microbial and other forms of life that can thrive in scalding, mineral-rich waters that percolates out of spreading ridges.

The scientists say they have explored just one small stretch of the Gakkel Ridge and hope to return in a few years.

"This will be a gold mine for deep sea research for many, many, many years," says Sohn.

Volcanic eruptions reshape Arctic ocean floor: study

Margaret Munro , Canwest News Service

Chunks of broken sea floor rock, or "talus ejecta" and large-grain pyroclastic deposits cover an outer slope of the Oden volcano on the seabed floor near the North Pole.