Scientists try to find underwater eruption

SEATTLE – A team of U.S. scientists set out Saturday for Pacific waters off British Columbia’s Vancouver Island, where they believe an underwater eruption is under way.

“We really don’t know what to expect,” said Edward Baker, an oceanographer at the Pacific Marine Environmental Laboratory. “If we’re very lucky, we may get pictures of brand-new lava on the seafloor.”

The lab is part of the U.S. Commerce Department’s National Oceanic and Atmospheric Administration.

They hope their observations will help improve understanding of the Juan de Fuca plate, a tectonic slab of the Earth’s crust. Its movements in conjunction with occasional volcanic activity can produce earthquakes and even large-scale tsunamis like the one that caused the Dec. 26 disaster in southern Asia.

The 20-member U.S. team has been scrambling since Sunday, when seismic monitors detected quake swarms 200 miles offshore. Most of the nearly 4,000 temblors have been tiny, but some have exceeded magnitude 4.

“It has been going on long enough that we’re pretty sure lava is moving,” Baker said.

The researchers keep scientific instruments packed and ready. Fortunately, a University of Washington research vessel is between assignments and available for the voyage.

Scientists from Hawaii, Oregon, Canada and Massachusetts will participate in the weeklong cruise, paid for by the National Science Foundation and NOAA.

“We know so little about what goes on when these volcanoes erupt,” said Joe Resing, an ocean chemist at the marine lab. “Opportunities like this are very rare.”

The rapid-response team has raced to seven underwater eruptions over the past 10 years.

Their tools include a network of Navy hydrophones designed to monitor enemy submarines. The instruments can detect distant underwater quakes that are not picked up by land-based seismographs.

“It’s left over from the Cold War, and it’s become very useful,” Baker said. “But even I’m not allowed to know where the microphones are.”

The sensors located the shaking on the Juan de Fuca Ridge, where fresh oceanic crust forms as tectonic plates pull apart and magma wells up from deep inside the earth. The seafloor spreading is slowly forcing the Juan de Fuca plate under the North American plate, creating a subduction zone that has unleashed massive earthquakes in the past.

An eruption along the ridge doesn’t directly raise the risk of an earthquake on the subduction zone, Baker said. But the regions are closely linked.

“They’re both expressions of the Juan de Fuca plate movement, and everything we can learn about how that movement is expressed will give us a better insight into the whole package.”

To try to figure out what’s going on nearly two miles below the ocean surface, scientists will lower instruments to collect samples and measure temperature, salinity and the chemicals and particles released by underwater eruptions.

“It’s sort of like drilling holes all over the Earth’s crust to look for oil,” Baker said. “We’re going to be drilling holes in the water to look for evidence of hot fluids.”

Though underwater volcanoes are little more than cracks in the crust, they produce the same plumes of gas as land-based volcanoes like Mount St. Helens, Baker said.

“If there’s a big eruption, it’s very obvious in the water.”

The team will also lower a camera-equipped sled to the ocean floor, hoping for a glimpse of lava.

Underwater lava may still be warm but it won’t be molten, said Resing, who as a graduate student used to scuba dive around Hawaii to study what happened to lava when it hit the water.

“It just cools instantaneously,” he said.

It’s also possible that magma hasn’t breached the surface yet, Baker said.

In that case, the photos will show how the volcanic unrest has affected the previously mapped seafloor and local marine life.