A new hydrothermal vent field, which scientists have dubbed "The Lost City," was discovered December 5th on an undersea mountain in the Atlantic Ocean. The unexpected discovery occurred at 30 degrees North on the Mid-Atlantic Ridge during an oceanographic cruise aboard the research vessel Atlantis. A team of scientists from the Scripps Institution of Oceanography, Duke University, the University of Washington and other institutions conducted the National Science Foundation (NSF)-supported expedition. "We thought that we had seen the entire spectrum of hydrothermal activity on the seafloor, but this major discovery reminds us that the ocean still has much to reveal, "says Margaret Leinen, NSF assistant director for geosciences.

"These structures, which tower 180 feet above the seafloor, are the largest hydrothermal chimneys of their kind ever observed," said Deborah Kelley, a University of Washington geologist and co-principal investigator on the cruise.

"If this vent field was on land, it would be a national park," added Duke University structural geologist Jeff Karson, a second co-principal investigator who, along with Kelly, dove in the submersible Alvin to the site.

Perhaps most surprising is that the venting structures are composed of carbonate minerals and silica, in contrast to most other mid-ocean ridge hot spring deposits which are formed by iron and sulfur-based minerals. The low-temperature hydrothermal fluids may have unusual chemistries because they emanate from mantle rocks.

Nothing like this submarine hydrothermal field has ever been previously observed, say the scientists. These events are unique, they believe, because they rest on one-million-year-old ocean crust formed tens of kilometers beneath the seafloor, and because of their incredible size. Dense macrofaunal communities such as clams, shrimps, mussels, and tube worms, which typify most other mid-ocean ridge
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Contact: Cheryl Dybas
cdybas@nsf.gov
703-292-8070
National Science Foundation
10-Dec-2000