Undersea Eruption Is Detected

On the site of deep-sea volcanic vents that nurture some of the most exotic life forms ever discovered, scientists are reporting a likely eruption a mile below the surface of the Pacific, about 300 miles off the Oregon coast.

It is deep enough, and small enough, so that there will be no visible effect on the ocean surface, and no creation of tsunamis, or seismic sea waves, said Stephen Hammond, director of the National Oceanic and Atmospheric Administration’s volcanic research program at Newport, Ore.

Hammond said last week that sounds recorded in the previous 10 days by Navy acoustic instruments are the same as those received during a confirmed eruption nearby in 1993.

That eruption, on the Axial Seamount, which rises from the Pacific floor to within about 5,000 feet of the surface, inspired dives by a submersible. The craft found six-foot-long worms and other creatures that came to the site to live on nutrients coming from the vents.

Hammond said the National Science Foundation will fund a weeklong exploratory voyage starting Monday by the Oregon State University ship, Wecoma.

He said the Wecoma will plant instruments on the sea floor to monitor seismic activity. There also are plans to establish a microbial observatory at the vents, which spew forth a hot soup of chemicals.

In recent days, there have been thousands of earthquakes--some up to magnitude 4.9--along the Axial Seamount, a portion of a sea floor spreading center about 50 miles south of the 1993 eruption.

A sea floor spreading center is a place along undersea mountain ridges where molten rock emerges from deep in the Earth, creating crust between dividing tectonic plates. This is occurring off the Pacific Northwest and part of Northern California, along the edges of the Pacific and Juan de Fuca plates.

The area off the Northwest has at least one undersea volcano that has come close to the ocean surface. Hammond said it is to the northwest of Axial, where the top of the Cobb Seamount is 90 feet below the surface.

Based on the 1993 eruption, and another that took place in 1996, the probable Axial eruption is expected to last several weeks.

“There are several things we are trying to learn with our research,” Hammond said. “What do these eruptions do to the chemistry of the ocean? How do they affect nutrients and the food chain? How do the chemical and thermal inputs affect the way the ocean moves and what influences do they have over the climate?

“It is most exciting to explore volcanic activity in this deep biosphere. It has the potential for immense practical applications. We are looking at the fundamental ways in which our planet functions.”