Exploring an Underwater Mountain

The research vessel Atlantis pulled out of the port of St. George in Bermuda recently and headed off to sea in search of a mountain.

Scientists from eight universities will spend a month aboard the ship, based at the Woods Hole Oceanographic Institution, in Woods Hole, Mass., searching for clues to a mystery. Their basic question: Why has a towering mountain risen from the ridges and hills along a fascinating geological structure called the Mid-Atlantic Ridge?

Far beneath the surface of the ocean, 12,000-foot Atlantis Massif is nearly twice as tall as other mountains in the area, and no one is certain why.

During the expedition, scientists will study the mountain with cameras and sonar, and take turns spending two weeks aboard the titanium-hulled submarine Alvin, snapping pictures and collecting rocks for analysis back in their labs. And the rest of us have been invited to go along for the ride.

Reports from the expedition will be published twice a week on the group’s Web site, and questions can be e-mailed to the scientists through their spokesman, Monte Basgall.

“We pulled out Saturday from St. George, Bermuda’s quaint first capitol, which is almost four centuries old,” Basgall tells me by e-mail. The ship set out on a “perfect morning,” he adds, and within moments the scientists had turned to the task at hand.

Young, But High Mountain

The Mid-Atlantic Ridge has long fascinated scientists because it is one of the regions on the Earth — all located under seas — where new crust is being formed. As the tectonic plates pull apart at the ridge, hot rocks from below to rise to the surface and cool into slabs of stone. Many centuries from now, the forces of nature will use some of those rocks to build new mountains along the shorelines, constantly reforming the planet we call home.

The ridge itself is enormous, winding south from Iceland for more than 6,000 miles, and it is one of the largest mountain ranges on Earth. But it is completely under water, usually at least 12,000 feet, except for the few areas where mountains poke through the surface. However, most of the mountains along the twisted, gnarled ridge are relatively modest.

That’s why Donna Blackman of the Scripps Institution of Oceanography in La Jolla, Calif., was so surprised when she and Joe Cann of the University of Leeds in the United Kingdom discovered Atlantis Massif while mapping the ridge a few years ago.

Mountains are common at mid-ocean ridges, but this one is a dandy. It is four to six times wider than other mountains in the area, known as abyssal hills, and it towers over its neighbors like, well, a mountain.

But since it is part of the ridge structure, it must be very young, geologically speaking, because it was formed from new crust welling up through the fissures along the ridge, which is also called a spreading center. Blackman wanted to know how it got there, and why it was so huge. By most reckoning, it should be a lot more puny.

She’s the chief scientist on the expedition. Co-principal investigators are Deborah Kelly of the University of Washington, an expert on the interaction of fluids with oceanic rock, and Jeffrey Karson, a structural geologist at Duke University.

Karson likens the ridge to a “taffy pull.” As the sea floor pulls apart, it becomes thinner, allowing molten rock to push through.

“Happening over and over again, that process produces new oceanic crust, and over geological times it re-paves the ocean basins repeatedly,” he says.

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