BUENOS AIRES, Argentina -- Scientists mapping the sea floor 600 miles northwest of Easter Island, in the South Pacific, have found what they say is the greatest concentration of active volcanoes on Earth.
Using sonar scanning devices to peer into the ocean depths, the scientists aboard the research vessel Melville were surprised to discover 1,133 seamounts and volcanic cones in an area about the size of New York state.
Many of the volcanoes rise more than a mile above the ocean floor, and some are almost 7,000 feet tall, with their peaks 2,500 to 5,000 feet below the sea's surface.
Two or three of the volcanoes could be erupting at any given moment, said Ken Macdonald, a professor of marine geophysics at the University of California at Santa Barbara who was a leading scientist on the project.
Mr. Macdonald, along with Tanya Atwater, professor of geological sciences at the University of California at Santa Barbara, and Don Forsyph, a professor of geophysics at Brown University, were surprised by the sheer number of volcanoes hTC they found while conducting surveys aboard the Melville from November to mid-January.
"We thought we would find a few dozen new volcanoes," Mr. Macdonald said. "Instead we found over 1,000 that had never been mapped before."
A marine geologist who was not part of the research team, Janet Morton of the U.S. Geological Survey in Menlo Park, Calif., said, "Though you would expect to find a lot of volcanoes there, 1,100 is a much greater density of activity than other parts of the sea floor."
There is no greater concentration of volcanoes on land either, specialists said.
Indeed, the finding underscores just how little is known about the ocean depths. Many scientists say that more is known about the mountains and valleys on the dark side of the moon than about the ocean floor, the last unexplored frontier on earth.
Mr. Macdonald estimated that no more than 5 percent of the sea bottom has been mapped in detail. Scientists said that one potential benefit of the discovery is that the volcanic eruptions are generating large new mineral deposits, including copper, iron, sulfur and gold.
Although the minerals cannot be commercially exploited now, future technological advances could make that possible, they said.
The discovery is also likely to intensify speculation over whether volcanic activity, pouring huge amounts of heat into the ocean, could change water temperatures enough to affect weather patterns in the Pacific, an idea that is greeted with skepticism by many scientists.
Scientists are particularly interested in determining whether periods of extreme volcanic activity underwater -- when perhaps a dozen or more volcanoes erupt simultaneously -- could trigger El Nino, a phenomenon that alters weather patterns around much of the globe every four to seven years.