Hydrothermal "Megaplume" Found in Indian Ocean

Brian Handwerk
for National Geographic News
December 12, 2005

An enormous hydrothermal "megaplume" found in the Indian Ocean serves as a dramatic reminder that underwater volcanoes likely play an important role in shaping Earth's ocean systems, scientists report.

The plume, which stretches some 43.5 miles (70 kilometers) long, appears to be active on a previously unseen scale.

"In a nutshell, this thing is at least 10 times—or possibly 20 times—bigger than anything of its kind that's been seen before," said Bramley Murton of the British National Oceanography Centre.

Scientists reported the finding last week at the fall meeting of the American Geophysical Union (AGU) in San Francisco. Researchers also announced newly discovered deep-sea hydrothermal fields in the Arctic Ocean and the south Atlantic.

The appearance of hydrothermal vents around the world suggests that they are a far more common part of the ocean system than once believed and could be a major influence on circulation patterns and ocean chemistry.

Scientists are only beginning to identify the tectonic conditions that may indicate where the fields can be found, but the possible locations are increasing.

"I'd be surprised if in the next five years we didn't experience a mini-revolution in terms of finding these [fields] in places where they are not supposed to exist," said geophysicist Robert Reves-Sohn of the Woods Hole Oceanographic Institution.

Volcanic Bombshell

Hydrothermal vents are volcanic hotspots that emit gasses and mineral-enriched water as hot as 760°F (400°C). The heat from these vents supports unique ecosystems where creatures survive using thermal and chemical energy in place of sunlight.

Megaplumes like the one found in the Indian Ocean are probably caused by undersea volcanic eruptions, though scientists aren't yet certain.

"Once formed they can possibly hang around for years," Murton said. The heat from such events could have a dramatic effect on ocean circulation, which plays a role in determining Earth's climate.

"The energy content is an order of magnitude greater [than ordinary plumes], and the thermal power may be many orders of magnitude greater," Murton said.

Continued on Next Page >>




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