Off Florida, a `lost city' of towers

Scientists plan to explore hydrothermal vent field populated by microbes

Medicine & Science

April 28, 2003|By Robert S. Boyd | Robert S. Boyd,KNIGHT RIDDER/TRIBUNE

A crew of scientists is heading into the Atlantic to survey what they call a "Lost City" of underwater towers and chimneys created by heat from the interior of the Earth.

The "city" -- first discovered in December 2000 -- is inhabited by primitive microbes, spurring speculation that life on our planet might have begun in just such an environment 4 billion years ago.

One of the spires is as tall as an 18-story building and sits amid a swirl of hot water rising from hydrothermal vents in the ocean bottom. The site is 1,500 miles off the Florida coast, atop a seafloor mountain ridge named the Atlantic Massif.

The scientists will spend a month exploring the vent field in the three-person submarine Alvin, which located the wreck of the Titanic in 1985. They will also use an unmanned robotic submarine equipped with cameras, chemical and biological sensors.

You can follow the expedition's progress on its Web site: www.lostcity.washington.edu.

The Atlantic structures are different from the so-called "black smokers" found on the floor of the Pacific Ocean since the late 1970s. The new towers are taller, whiter and cooler than their Pacific cousins. Also, they are formed by a process that has been seen nowhere else.

In the Pacific, smokers rise above undersea volcanoes and magma chambers -- huge pots of molten rock -- along huge cracks in the sea floor. The cracks are created when the giant tectonic plates that make up the Earth's surface pull apart. Water temperatures reach as high as 700 degrees Fahrenheit.

In contrast, the Atlantic vent field sits on a 1.5 million-year-old slab of crust that has been stripped to the underlying rocks. Seawater penetrates into the hot rocks, generating a chemical reaction that produces water rich in hydrogen and methane gas, a tasty diet for microorganisms.

The buoyant brew, ranging from 100 to 165 degrees Fahrenheit, floats up into the cold seawater. When the hot and cold fluids mix, chemicals separate and solidify, piling up into the mounds and spires that earned the name Lost City.

Unlike the Pacific smokers, which are dark and sulfurous, the Atlantic structures are nearly 100 percent carbonate, like the limestone in caves. Their color is white, cream or gray. In some places, they are covered with a mat so thick with microbes that the minerals cannot be seen.

The international crew, which will be based aboard the research ship Atlantis, consists of 24 scientists sponsored by the National Science Foundation, a U.S. government agency. Expedition leaders are Deborah Kelley, an oceanographer at the University of Washington in Seattle, and Jeff Karson, a professor of earth and ocean science at Duke University in Durham, N.C. Kelley and Karson were aboard the Alvin when it first spotted the Lost City, but were unable to take more than a brief look.

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