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Alvin to Explore Underwater Mountain

ST. GEORGE, BERMUDA -- An international team of scientists, including a geology professor and three graduate students from the Nicholas School of the Environment at Duke University, will leave Bermuda Saturday on a four-week expedition to an underwater mountain at the Atlantic Ocean's middle. For two of those weeks, the research submarine Alvin from the Woods Hole Oceanographic Institution in Massachusetts will take investigators thousands of feet deep to explore the 12,000-foot mountain's features, including its smooth corrugated top and its steep, landslide-exposed slopes. Computer browsers around the world will be able to keep track of the expedition by calling up periodic updates from the Woods Hole research vessel R/V Atlantis, to be posted on the Internet each Tuesday and Thursday, from Nov. 14 to Dec. 14, except for Thanksgiving Day at http://earthguide.ucsd.edu/mar. They will also be able to relay questions to the scientists by e-mailing mbasgall@atlantis.whoi.edu. The goal of the researchers, who come from eight different institutions, is to answer some of the many remaining mysteries about how Earth makes new skin. That process, called seafloor spreading, is perpetually underway along a globe-straddling line of volcanically active ridges where fresh crust is created. Girding our planet like a baseball's seams, these mid-ocean ridges define the surface edges of the huge, slowly moving plates that floor all oceans. As those plates inch apart, older existing crust atop their boundaries thins and stretches. That opens up conduits for hot magma from the inner Earth to flow up as molten lava. "Happening over and over again, that process produces new oceanic crust; and over geological times it re-paves the ocean basins repeatedly," said Jeffrey Karson, a Duke structural geologist and professor who is one of the expedition's three co-principal investigators. The mountain this expedition will target is located next to the Atlantic Ocean's spreading center -- the Mid-Atlantic Ridge -- but is about 5,000 feet taller than the usual mid-ocean ridge crest. There is also little evidence of lava, the normal building material for crust. Karson and others on this cruise have visited similar structures elsewhere along mid-ocean ridge lines. Co-discovered by the expedition's chief scientist, Donna Blackman of the Scripps Institution of Oceanography in La Jolla, Calif., this mountain is part of a very young sea floor, clearly a new addition to the Earth's crust. The scientists want to know what forces pushed it up to such a great height. According to one theory, when the normal magma supply stops for a period of time where the crust is thinning, cracks that geologists call faults could form in a way that uplifts rocks normally deep underground. The process is something like a "taffy pull," Karson said. "As it pulls apart horizontally, it gets thinner vertically." Under those circumstances, changes in the underground balance of forces could raise such a high mountain. Another process may also be at work. As faults form where the crust is thinning, seawater could pour into them. If those cracks extend deep enough, the water could contact hot olivine-bearing rock from Earth's mantle, which underlies the crust. That interaction could form a new material called serpentine, which would swell the mantle rock's volume to make it less dense. Being less dense, the rock would rise and the upward push may have helped create the mountain. Deborah Kelley, a research assistant professor at the University of Washington's School of Oceanography in Seattle and a world expert in the interaction of fluids with oceanic rock, will serve as the expedition's third co-principal investigator. Expedition scientists will test these ideas using sophisticated devices operated and maintained by Woods Hole engineers and technicians on the R/V Atlantis. First deployed from the ship will be the DSL-120, a deeply towed side-scan sonar that uses sound wave reflections and absorptions to "paint" electronic and paper maps of the terrain it passes over. That will be followed by Argo-II, a camera-bearing towed instrument package that Atlantis can maneuver into surprisingly tight spaces to provide digital and photographic images of the sea floor. The most spectacular tool will be Alvin, a titanium-hulled submarine that can carry two reseachers and a pilot to depths of as much as 14,764 feet for as long as eight hours. Wedged in Alvin's cramped cockpit, the scientists will look through the submarine's small 3 1/2-inch thick windows and use an array of cameras to make invaluable personal observations. In addition, the submarine has two external robot arms to grasp and break off rock samples for later chemical studies. At the expedition's height, the decks of the R/V Atlantis will become a separate study in group dynamics as scientists, technicians and the ship's crew work in shifts around the clock to launch, operate and retrieve the various submersible vehicles; sort and study recovered rock specimens, monitor scientific instruments and video screens; log data and transcribe their taped dictations made during Alvin dives; strategize for the next day's activities; and somehow manage to find the time to eat and sleep. Other Duke participants will include Nick Bacher, a graduate student studying paleoclimatology and geochemistry under geology professor Paul Baker; Heather Hanna, a graduate student in igneous petrology and geochemistry studying under associate geology professor Emily Klein; Peter Rivizzigno, a graduate student in structural geology whose adviser is Karson; and Monte Basgall, a senior science writer at Duke's Office of Research Communications.