Finding the Lost City

Unexpected Discovery Sheds Light on the Earth's Secrets

by Monte Basgall

"It’s just such a vivid reminder of how little we really know about the sea floor, and our planet in general," muses Jeffrey Karson, a geology professor at the Nicholas School’s Division of Earth and Ocean Sciences, almost two months after his group discovered "The Lost City" in the middle of the Atlantic Ocean.

"It’s nice when all of a sudden you have this explosion of new ideas and information handed to you. It’s something to really enjoy while it’s happening. But I would have to also say that there was a lot of luck in finding these."

The almost magical unexpected discovery transformed an interesting, but frustrating, international scientific expedition to an enigmatic underwater mountain. Karson, one of three principal investigators on the cruise, saw the magic begin unfolding shortly after midnight last Dec. 4th inside a darkened control room aboard the research vessel R/V Atlantis.

Peering at TV monitors that relayed floodlit video images from Argo-II, a camera-bearing underwater probe, scientists from eight different institutions in three countries had already been working in shifts over seven nights of surveying the mountain, which loomed about 3,000 feet below the ship. But everything changed when they saw the first signs of a beautiful and novel hydrothermal vent field there.

The expedition, which included Karson and three Nicholas School graduate students, had sailed from Bermuda on Nov. 11 bound for a point halfway to Morocco. Their ship, based at the Woods Hole Oceanographic Institution in Massachusetts, had steamed about four days to reach the Mid-Atlantic Ridge system, a zigzagging seafloor rift where Africa and Europe are slowly separating from North and South America.

According to the widely accepted Plate Tectonics theory, the huge plates that bear those continental masses are moving apart there at an average rate of 0.8 inches a year. As the plates separate, hot magma upwells from Earth’s underlying mantle to heal the resulting cracks in the ocean floor. This magma spews out as lava through volcanoes that form there, and the lava eventually re-pave the ocean floor with fresh crust.

That’s the way the Mid-Atlantic Ridge system is usually thought to behave. But the scientists were visiting this mysterious mountain, an imposing structure that geologists call a "massif," to validate or disprove suggestions that it formed very differently.

Rising more than 12,000 feet, the massif is taller than the typical Mid-Atlantic Ridge seamount. And rocks previously dredged up from its slopes suggested that something other than volcanism may have helped push it up.

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