"City" of Ancient Rock Found at Bottom of Atlantic Ocean

ABCNews.com

July 13, 2001

More than 2,000 years ago, the Greek philosopher Plato wrote about a splendid city named Atlantis, with fertile soil and glorious temples, that "in a single day and night of misfortune…disappeared into the depths of the sea."

Now, researchers probing the ocean bottom have found 18-story-high towers of stone deep in the ocean near a section of volcanic fault ridges that extend for 6,200 miles along the Atlantic Ocean floor.

The majestic height of the two dozen stone structures and their location on a seafloor mountain named Atlantis Massif inspired the scientists to name the area "Lost City," in honor of the fabled, flooded city referred to by Plato.

The underwater stone spirals are unusual for their composition and location. Scientists think they may offer a glimpse into the earliest environment of Earth, when life began, and may host as yet undiscovered forms of life.

"It was clear these were unlike anything we'd ever seen before," said Deborah Kelley, an oceanographer at the University of Washington. She was one of three people who traveled to the newly discovered underworld in a submersible vessel.

Mountain With "Fingers"

Researchers have found in volcanic cracks on areas of the ocean floor about 100 underwater vent systems composed of mineral deposits. Colonies of strange, primitive creatures, including blood-red tubeworms and large clams, feed on nutrients leached by hot, dissolving gas from the vents.

But this network of stone is unique. Instead of being formed around volcanic vents, the stone structures are about nine miles from the cracks. The towers extend like groping fingers above Atlantis Massif, a submerged mountain about the size of Mt. Ranier in Washington State.

Jeff Karson, an oceanographer who explored the area with Kelley, said: "If this were on land, this would be a national park."

The Lost City is also strikingly bright—brighter than the usual conditions in which things can generally be seen using artificial light a half-mile below sea level.

Although other rock formations around volcanic ridges have appeared black, the newly discovered formations are gleaming white because they are made up of materials similar to those of pale concrete, such as carbonate minerals and silica. Kelley, the lead author of a report on the formations in the July 12 issue of Nature, said the steep-sided towers of rock blossom into feathery ledges of precipitated stone that sprawl outwards for as wide as 30 feet.

Most unusual about the structures are their size. The highest stone spiral reaches 180 feet above the ocean floor.

Until this discovery, the highest known underwater structure was an 80-foot-high stone chimney known as "Godzilla," located on the seafloor off the coast of Washington State. "Godzilla" cracked in half and toppled to the seafloor three years ago.

Heat From Green Rock

The towers of Lost City were able to grow so tall in part because they are nine miles away from the volcanic vents of the Mid-Atlantic Ridge. This distance buffers the rocks from volcanic eruptions that occur once every five to ten years at the ridge's axis and from earthquake activity that's more frequent around the vents.

But their distance from the underwater vents also suggests that the towers must be formed by a unique process.

In so-called "black smoker" formations, ocean water sloshes near hot magma at the volcanic vents and then heats up to 750 degrees Fahrenheit. The hot water absorbs minerals and chemicals from surrounding rocks and eventually flows upwards. As the hot water rises, it cools and releases the minerals and chemicals, which form towers of dark mineral rock and nutrient-rich ecosystems.

In Lost City, the construction of the stone towers appears to be driven not by hot magma but by a rare rock. Sections of a glassy green rock known as olivine are exposed directly under small cracks in the ocean floor. When ocean water seeps into this 1.5-million-year-old mantel rock, it reacts with the olivine to form a scaly, dull green rock known as serpentine.

This reaction generates heat, which triggers the same building of mineral deposits as seen at black smokers. But the deposits at this site are made of a different, paler rock.

"The fluids coming out of these cracks at Lost City have not been found before," said Karen Von Damm of the Institute for the Study of Earth, Oceans and Space at the University of New Hampshire. "So it's likely there's also new life there that hasn't been found before."

By "new" life, Von Damm means undiscovered life that may be very ancient. Some people believe any life around the chalky towers of Lost City may resemble the earliest life-forms on Earth.

Like Primitive Earth?

Unusual life-forms called Archaea have been found around traditional oceanic vent systems. These animals have been placed near the bottom of the evolutionary time scale. Scientists believe any life-forms near Lost City might be even more primitive.

Any animals living near Lost City would exist in temperatures of about 160 degrees Fahrenheit—below the scorching temperatures of other hydrothermal vents and closer to what is thought to have been the early climate of Earth. The new vents also have high pH levels, or low acidity, which some scientists believe also may have been present when life began on the planet.

The site also produces high levels of methane, which the most ancient forms of bacteria are thought to have feasted on billions of years ago.

"The area conjures up the origins of life," said Richard Lutz, an oceanographer at Rutgers University who, in the late 1970s, was among the first oceanographers to explore the first hydrothermal vent system ever discovered. "There's a good case that this could have been the kind of environment where life began."

Copyright 2001 ABCNews.com