OREGON STATE UNIVERSITY

ERUPTIONS, VOLCANIC WONDERLAND FOUND IN DEEP SEA

05/13/2004

NEWPORT, Ore. - Oceanographic researchers who just completed a study of undersea volcanoes in the Mariana Arc south of Japan have discovered what the Cascade Range of Oregon, which has a similar geologic setting, might look like if it were buried deep beneath the sea - and erupting.

Instead of forested slopes, fresh alpine air and snow-capped peaks, this type of volcanic mountain range would feature plumes of molten sulfur, other-worldly life forms based on chemical energy instead of sunlight, "black smokers" churning hydrothermal fluids and sometimes explosive undersea eruptions.

Some cones look like an underwater version of Mount Hood, while others resemble Crater Lake.

This expedition, which for one of the first times in history was able to witness a small undersea eruption of an active volcano, was an enormous success, said Bill Chadwick, a volcanologist with the Cooperative Institute for Marine Resource Studies at Oregon State University.

The institute, based at OSU's Hatfield Marine Science Center, works closely with the agency that organized the expedition, the Pacific Marine Environmental Laboratory of the National Oceanic and Atmospheric Administration.

"We were just going from one incredible event to the next, seeing things we had never witnessed before," said Chadwick, who was a key participant on this exploratory cruise largely funded by NOAA's Ocean Exploration Program. "It was very exciting, and quite remarkable in that every volcano we visited seemed to be unique in its own way."

The researchers made new findings about how life based on photosynthesis in the upper layers of the ocean makes a gradual transition to life further down based on chemosynthesis, or chemical energy - odd microbes, snails, barnacles and worms clinging to hydrothermal vents. They found an enormous variation in geology and life forms, which may lead to the identification of new species. One volcano appeared to have had a catastrophic eruption in its past and had formed a huge caldera just about the same size as the one which holds Oregon's Crater Lake, within prehistoric Mount Mazama.

They found carbon dioxide spewing from rocks under such enormous subsea pressure that it emerged as a bubbling liquid in one site named "champagne vent." And they had to back their equipment away from one ongoing eruption at a site named "Brimstone Pit" when the belching sulfur, acid, boiling water and rocks became too intense.

The basic geology of the Mariana Arc, which includes such islands as Guam, Saipan and Iwo Jima, is conceptually similar to the Cascade Range of the Pacific Northwest. Both are on the Pacific "Ring of Fire," and in each case, an oceanic plate is being subducted underneath another of the Earth's major crustal plates, and ultimately causing a string of volcanoes above the point where the subducted plate begins to melt.

In Oregon, that results in the Cascades, which have volcanism ranging from fairly benign lava flows to the catastrophic eruptions such as Mount St. Helens, along with hot springs and other features.

In the western Pacific Ocean, the same activities are taking place on the oldest and deepest seafloor in the world. The Challenger Deep in the Marianas Trench, for instance, is the deepest part of the world's oceans, at 35,838 feet. If Mount Everest were cut off at sea level and placed there, its peak would still be a mile underwater.

But beneath the surface of the ocean, scientists are now discovering a murky and exceedingly active group of volcanoes that appear to rival any of their terrestrial cousins. The most recent visit was the culmination of a two-year, $2 million project funded by NOAA's Ocean Exploration Program, aboard the R/V Thomas G. Thompson and using a remotely-operated undersea vehicle called ROPOS. In the past, scientists say, much of this type of research was done at "spreading centers" such as the mid-ocean ridges, where new ocean floor is formed. This time, they examined the volcanoes that occur when plates collide and ocean floor is eventually melted and recycled deep within the Earth.

The work was a collaboration of scientists from NOAA, OSU, the University of Washington, University of Victoria, U.S. Geological Survey, and other institutions, including scientists from Canada, New Zealand and Japan.

Using ROPOS, the researchers were able to take video, make scientific measurements and recover samples at sites ranging from about 70 feet deep to almost a mile. They explored both the peaks and flanks of seven volcanoes, and near their summits often found seafloor hot springs and unique biological communities that depend on them.

These types of volcano are generally more conical and explosive, Chadwick said.

"One of the most dramatic events was the eruptive activity on Northwest Rota 1, a volcano about 60 miles north of Guam," Chadwick said. "At a depth of about 540 meters in what we called Brimstone Pit, there was a large plume of hot water, drops of molten sulfur, bursts of rocks. It would be considered a pretty small event by volcanic standards but it was definitely eruptive and one of the first times we've ever seen and recorded anything like that beneath the ocean."

At other sites, the researchers found black smokers, which are chimneys made from spewing minerals and hydrothermal vents. In the past, such vents have usually been observed only deep beneath the sea. But on the upper flanks of these volcanoes, some of them had schools of tropical fish, tuna or sharks swimming nearby. One site had so many chimneys it was named the "Black Forest," with some of these bizarre chemical vents up to 30 feet high.

"As the ROPOS came closer to the surface, where sunlight was able to penetrate, it was just a riot of life with incredible amounts of fish and corals," Chadwick said. "And we found at least some life forms, such as one type of spider crab, that could live in either environment, either the one based on sunlight or the one based on chemicals. Most scientists believe life on Earth may have originated in deep ocean vents."

It will still take the researchers some amount of time to compile, analyze and publish all the data that emerged from these cruises, Chadwick said, which only concluded in late April. Scientists in Washington, D.C., today announced some of the findings from this cruise, and more information on the expedition can be obtained at the web site of NOAA's Ocean Exploration Program, at http://oceanexplorer.noaa.gov/explorations/04fire/welcome.html.

"Unlike much scientific research, this type of expedition is a little riskier, because you often have no idea what, if anything, you will find," Chadwick said. "But this research provided some remarkable findings, some things never seen before, and allowed us to learn about a portion of the world that had not been explored before."