A hot vent find in the Atlantic.

This summer, a team of oceanographers on its way to track down the exact sites of the low-temperature hydrothermal vents, or undersea geysers, it had found on the Mid-Atlantic Ridge last year (SN:10/20/84, p.246) made an even steamier discovery. While retrieving some current meters at another hydrothermal field along the ridge, the scientific party aboard the National Oceanic and Atmospheric Administration (NOAA) ship Researcher found the telltale signs of enhanced hydrothermal activity in water samples. They

decided to abandon their original plan to cruise father south, and three weeks later zeroed in on a cluster of at least 11 high-temperature vents--"black smokers" that were vigorously spewing out blackened, mineral-laden water just like their counterparts along the East Pacific Rise.

The find is remarkable not only because it adds to the number of vents found in the Atlantic but also because it is the first example of high-temperature venting along a slow-spreading ridge. Traditionally scientists have hunted for undersea geysers along ridges where seafloor is being created rapidly; the East Pacific Rise, for example, churns out new ocean floor about 10 times faster than the Mid-Atlantic Ridge. But since 1972, when the first evidence of low-temperature venting was found along the Mid-Atlantic Ridge, oceanographers have come to understand that fast-spreading ridges dont't have a monopoly on venting.

Finding high-temperature vents fortifies the view that slow-spreading ridges -- which account for half of the world's ridge network--may contribute much more to the oceans' chemical and thermal budgets than previously thought. In addition, the recent find demonstrates that there is enough heat available under slow-spreading ridges to drive black smokers--an idea that was in question before the cruise, says Researcher chief scientist Peter Rona at NOAA in Miami. Rona also reports that the group dredged polymetallic sulfides from the floor, a find suggesting that the Atlantic may house more economically important resources than had been assumed.

Rona's group, which includes researchers from the University of Cambridge in England and the Florida Institute of Technology in Melbourne, has yet to analyze in detail the water and sediment samples collected during the July 9 to Aug. 7 cruise. Preliminary results will be presented at the December meeting in San Francisco of the American Geophysical Union. The researchers would like to return to the vents with a submersible to examine them in detail and to collect samples of the hot, bubbly fluids from the mouths of the vents.