Signs of eruption found off Oregon shores.

Braving winter seas whipped to a fury by El Nino-powered storms, a crew of oceanographers visited a submerged volcano this month and pulled up evidence of a recent eruption some 500 kilometers west of the Oregon coast.

"We were very fortunate to get anything," says Robert W. Embley of the National Oceanic and Atmospheric Administration (NOAA) in Newport, Ore. The wind and waves were rough enough to break a plug in the ship's hull, allowing water to pour in and ruin two computers.

The research vessel Wecoma set off on Feb. 9 for Axial volcano, a broad-shouldered mountain whose summit rises to within 1,350 meters of the ocean surface. Axial has captured the attention of marine scientists over the last few years because it appears to be active and it sits directly atop a section of the midocean ridge system. Along the length of this 65,000-km chain girdling the globe, the seafloor spreads apart to form new ocean crust.

Arriving at the volcano, the researchers discovered a dramatic increase in the amount of warm water spewing out of the summit depression, called a caldera. They also found microscopic shards of glassy rock in the fluids, suggesting that fresh molten rock had forced its way up through the crust and erupted on the seafloor within the last month. The team could not collect proof of an eruption because Wecoma lacks equipment to image the seafloor.

Researchers at NOAA first detected hints of the recent activity at Axial volcano on Jan. 25, when an underwater network of microphones picked up a flurry of earthquakes coming from the caldera. The earthquake swarm continued for more than a week, sometimes spawning more than 100 quakes per hour. The majority ranged in size between magnitude 2 and 3, although three quakes exceeded magnitude 4, says Christopher Fox of NOAA.

This is the third time marine scientists have detected quake swarms on the underwater sound surveillance system. The NOAA team observed swarms in 1993 north of Axial and then in 1996 southeast of the volcano. In both previous cases, researchers quickly visited the sites and documented recent eruptions.

The event at Axial volcano will yield more detailed information than the previous eruptions because scientists have been collecting baseline data at the volcano and can therefore evaluate how it has changed, says Edward T. Baker of NOAA in Seattle, a chief scientist on the Wecoma.

Last summer, Baker and his colleagues tethered instruments to the seafloor on top of Axial volcano. If the devices have survived the eruption, they will provide data about water currents and temperature, earthquakes, and seafloor tilting and spreading. The researchers will return to the volcano this summer with underwater cameras to image the ocean bottom and to collect the sensors. "That's going to be a crushing blow if we have all these instruments there and they turned out to be too close [to the eruption]," says Baker.

Although Axial forms part of the global midocean ridge, most other ridge segments do not form broad, high volcanoes, says Rachel M. Haymon, a marine geologist at the University of California, Santa Barbara. Nonetheless, the activity at Axial can help scientists learn lessons about the eruptions creating new crust along the ridge system. "It's so hard to document what is going on down there. To have some evidence of it is important," she says.