UW News

May 20, 2004

A rare sight: Eruption on the sea floor surprises researchers at Northern Mariana Islands

News and Information

As one watches the clip of footage from the sea floor one hears the voices of scientists and technicians at the monitors in the control room on board the UW’s research vessel Thomas G. Thompson.

“That could have been an avalanche — right?” one asks.

Someone else later, “I mean this is spectacular. I doubt that anybody has ever seen this before.”

Indeed, the eruption of a sea floor volcano — this one spewing gas, rock and molten sulfur — has never been seen before, according to David Butterfield, UW affiliate associate professor of oceanography and senior scientist with the Joint Institute for the Study of Atmosphere and Oceans. On April 1, scientists witnessed such an event on the sea floor in the Northern Mariana Islands, a string of 14 islands in the western Pacific.

“We have seen eruptions in Hawaii in the shallow water on the flank of Kilauea,” Butterfield said. “We have seen very shallow seamounts explode through the sea surface off of Iceland and in the Pacific. But nobody has ever directly witnessed the eruption of a deep submarine volcano.

“At a submerged volcano near Rota, an island north of Guam, we saw some kind of eruptive activity, and our interpretation is that it was an explosive gas eruption that threw out small pieces of rock ‘lapilli,’ molten sulfur and billowing clouds of particulate sulfur.”

Butterfield monitored water conditions and determined the fluid was very corrosive so the operator backed the remotely operated vehicle out of there. The vehicle, a Canadian submersible, came to the surface coated with small balls of sulfur.

See a video clip “incredible vista of Brimstone Pit” at http://www.oceanexplorer.noaa.gov/explorations/04fire/logs/april01/april01.html.

NOAA scientist Bob Embley led the 21-day expedition on board the UW’s 274-foot vessel. The Mariana Arc is part of the volcanic mountains around the Pacific rim known as the ring of fire and which, on this side of the world, includes volcanic mountains in the Pacific Northwest and on the sea floor off our coast.

At a volcano north of Saipan, the scientists found an ancient caldera, collapsed in the center and about the size of the one that holds Crater Lake in Oregon. A string of hydrothermal vents there may be the shallowest active sulfide vents yet seen.

One of the rock pinnacles was tall enough to reach from the sea floor where it is pitch black into the part of the ocean where sunlight can penetrate. There the scientists documented the overlap of organisms from a “chemosynthetic” ecosystem fed by the chemicals from hydrothermal vent fluids and a “photosynthetic” ecosystem where such things as soft corals and red algae depend on sunlight for energy.

See http://www.oceanexplorer.noaa.gov/explorations/04fire/logs/april05/april05.html for images of the clear, filmy microbial mat, the result of vent fluids wafting up from below, coating the sunlight-dependent corals and such on the pinnacle, all while tropical fish swim by.

Nobody has ever seen this in an oceanic environment before, Butterfield said. The organisms seem to cohabit the area just fine, and scientists are interested in knowing if they are sharing energy in some way, or if fish are eating the microbial mats as they have been seen to do other places.