Scientists Find 'Lost City' of Ancient Rock
July 11, 2001 -- More than 2,000 years ago, the Greek philosopher Plato wrote about asplendid city named Atlantis with fertile soil and glorious templesthat "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 — the tallest ever — near a section of volcanic fault ridges that extend for 6,200 miles along the Atlantic Ocean floor.
Inspired by the formations' majestic heights and by the fact that the stone towers appear on a seafloor mountain named Atlantis Massif, the scientists named the field of about two dozen stone structures The Lost City in honor of the fabled, flooded city.
Not only are the underwater stone spirals unusual in composition and their location, scientists think they may offer a glimpse into Earth's earliest environments when life began.
"It was clear these were unlike anything we'd ever seen before," says Deborah Kelley, an oceanographer at the University of Washington and one of three people who traveled to the newly discovered underworld in a submersible vessel.
A Mountain With Fingers
Scientists have found about 100 other underwater vent systems made up of clusters of mineral deposits around volcanic cracks in the ocean floor. 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. Rather than forming directly around volcanic vents, the formations are about 9 miles from the cracks. The towers extend like groping fingers above Atlantis Massif, a submerged mountain about the size of Washington's Mt. Ranier.
As Jeff Karson, an oceanographer who explored the Lost City with Kelley remarked, "If this were on land, this would be a national park."
The Lost City is also strikingly bright — or as bright as things can appear under artificial light a half-mile below sea level.
While rock formations around volcanic ridges normally appear black, these formations are gleeming white because they are made up of materials similar to pale concrete, such as carbonate minerals and silica. Kelley, who was lead author of a study about the formations in this week's issue of the journal, Nature, says the steep-sided towers of rock blossom into feathery ledges of precipitated stone which 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.
Before finding Lost City, the highest known underwater structure was an 80-foot-high stone chimney known as "Godzilla" on the seafloor off the Washington state coast. "Godzilla" cracked in half and toppled to the sea floor three years ago.
Heat From a Green Rock
Part of the reason Lost City's sea-scrapers could grow so high is because they're located 9 miles away from the volcanic vents of the Mid Atlantic Ridge. This distance buffers the rocks from volcanic eruptions that occur once every 5-10 years at the ridge's axis and from earthquake activity that's more frequent around the vents.
But the structures' distance from the underwater vents also suggests 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.
At Lost City, the construction of the stone towers appears to be driven not by hot magma, but by a rare rock. In this region, 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 these deposits are made of a different, paler rock.
"The fluids coming out of these cracks at Lost City have not been found before," says 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, and this life might in fact be very ancient. Some believe any life around the chalky towers of Lost City could resemble Earth's earliest life forms.
Lost City Like Earliest Earth?
Unusual life forms called Archaea have been found around traditional oceanic vent systems and these animals have been placed near the bottom of the evolutionary time scale. Scientists believe life around Lost City might be even more primitive.
Animals around Lost City would be living in temperatures a little more similar to Earth's suspected early climate — around 160 degrees Fahrenheit, compared with the even more scorching temperature at hydrothermal vents. The new vents also have high pH levels — or low acidity — which some have proposed was also present when life began on the planet.
Finally, the site 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," says Richard Lutz, an oceanographer at Rutgers University who was among the first oceanographers to explore the first hydrothermal vent system ever discovered in the late 1970s. "There's a good case that this could have been the kind of environment where life began."
Kelley is eager to return to the Lost City site since she and her team discovered the field too late in their expedition to explore it for more than one dive. But Lutz hopes to get there first when he sets off in two weeks to relocate the underwater city for an IMAX film project.
No matter who sees the Lost City next, Karson suspects there may be many more out there left to discover.
"In science there can be a prevailing notion that we understand everything and can predict everything," he says. "But this is a vivid reminder that we're still in era of exploration."