15 December 2005

Deep sea gardens discovered everywhere

Seafloor hot vents, like this one, are powering undersea gardens around the world, researchers are finding (Image: OAR/NURP; NOAA; P Rona)Ocean explorers are uncovering a whole gaggle of new undersea gardens from the Arctic to the Indian Ocean powered by nothing but hot water, and rich in both exotic life and valuable ores.

Geothermal vents on the ocean floor had previously been thought possible only in places like the eastern Pacific, where the relatively rapid spreading apart of tectonic plates creates seafloor volcanic activity to power the fields of smoking hot water.

Now, scientists have found vents in the Arctic Ocean, along the mid-Atlantic Ridge and discovered a vastly productive hot water spout in the Indian Ocean.

"Up to 20 years ago all these new discoveries were in regions that were off-limits," says hydrothermal vent specialist Professor Peter Rona of Rutgers University.

In other words, they were in places where the seafloor is spreading apart more slowly than in the eastern Pacific.

In 1985, Rona led an expedition to a hydrothermal site known as TAG that had a huge mound of hydrothermally created iron, copper, zinc, gold and silver ores about 3 kilometres underwater along the mid-Atlantic Ridge.

"It changed the picture of seafloor hot springs from regional to global," Rona said at a recent meeting of the American Geophysical Union in San Francisco.

Adding chemicals to oceans
Among the important implications of more hydrothermal fields is that they are contributing significant quantities of chemicals to the oceans as well as helping to cool the Earth's interior, rather like a radiator in an automobile.

"We're a water-cooled planet," says Rona.

So far, known hydrothermal vents put out about 17 terawatts of power, equivalent to about half the energy produced by humans, says Dr Robert Reves-Sohn of Woods Hole Oceanographic Institution.

But with just 10% of the world's ocean ridges explored, there are bound to be a lot more hydrothermal vent fields out there, he says.

Mining ores
Another lesson learned from the new vents has been how and where valuable metal ores get laid down in the first place, says Rona.

The TAG mound is too deep to mine in any practical way, he says, but it has sent economic geologists scurrying around the globe looking for ancient, dead forms of the same mounds that have found their way onto land via plate tectonics.

Similar deposits are the source of a great deal of the world's historic copper ore.

As for the life forms on these new vent fields, they are proving to be exceptionally diverse, says Rona.

"We're finding that creatures will use anything to make a living," says hydrothermal vent researcher Dr Colin Devey of the University of Kiel in Germany.

Source: abc.net.au/science/news/enviro

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