Dec. 17, 2009  -- Scientists today unveiled rare video of the deepest underwater volcanic eruption ever seen, at a site where scorching 2,500-degree lava explodes into cold seawater nearly a mile below the ocean surface.

"It was very exciting. We've never seen anything like that on the ocean floor," said Bob Embley, a marine geologist at NOAA's Pacific Marine Environmental Laboratory in Newport, Oregon.

The West Mata volcano was discovered below the Pacific Ocean in an area between Samoa, Fiji and Tonga. It is six miles long and four miles wide, rising one mile from the sea floor. The top of the volcano sits 4,000 feet below the surface of the water.

Last May, scientists on board the research ship Thomas Thompson deployed a remote-controlled vehicle called Jason to get close to the rumbling volcano as it ejected molten bubbles of lava three feet across. Embley described the scene as "an underwater Fourth of July."

Samples collected near the volcano showed the seawater to be highly acidic, similar to battery or stomach acid, researchers said. Despite the harsh conditions, scientists found and photographed a species of shrimp apparently thriving near the volcanic vents.

"Nobody would have predicted that things would have survived long enough in water that acidic. It seems like it's too harsh a condition," said University of Washington chemical oceanographer Joseph Resing.

The volcano is spewing a type of lava known as Boninite, which until now had only been seen in extinct volcanoes more than a million years old.

'A Very Rare Thing'

"Most of the eruptions on Earth happen underwater, and you would think by now we would have seen one. It's a very rare thing that we've never seen flowing molten lava until now," said Resing, the mission's chief scientist.

Scientists hope deep-ocean eruptions can tell them more about how the planet recycles heat and matter at the friction points where Earth's tectonic plates meet. They also hope to learn more about how carbon dioxide and sulfur gases cycle through the ocean.

Volcano a Mile Beneath the Pacific

The National Science Foundation and National Oceanic and Atmospheric Administration paid for the research, which is being presented at the American Geophysical Union's annual science meeting in San Francisco.

West Mata lies within the Pacific "Ring of Fire", where volcanoes are common.

In the Philippines, authorities are moving 30,000 people away from the danger zone near the erupting Mayon volcano.