Strong quake, eruption near Tonga prompts tsunami warning

The Associated Press ,  Nuku'alofa, Tonga   |  Fri, 03/20/2009 3:25 PM  |  World

A powerful earthquake struck on Friday in the Pacific Ocean, shaking an erupting underwater volcano off Tonga's main island and raising fears of increased lava and ash flows, officials say.

There were no immediate reports of injury or damage from the 7.9-magnitude quake which was felt more than 3,000 kilometers away in New Zealand. A tsunami warning for islands within a 1,000 kilometer radius of the epicenter was canceled two hours later.

"We are quite lucky there was no tsunami," Tongan government chief seismologist Keleti Mafi told Associated Press.

However, the powerful quake will directly affect the eruption of the volcano about 10 kilometers from the southwest coast of Tongatapu island, and could lead to more molten lava and ash flowing into the sea, Keliti said. A column of smoke and steam could be seen rising 20 kilometers into the sky.

"The strength of the earthquake was enough to crack the volcano's [undersea] vent and allow more magma to be ejected," Mafi said.

A check of the volcano on Thursday from a boat 3 kilometers away from the vent showed about "a 10 cone of lava at the vent," standing up out of the ocean.

"It's grown out of the sea," he said, adding that it was very risky getting close to the volcano at this stage.

With much of the vent still underwater, most of the ash from the eruption has gone into the water rather than into the air.

David Bellwood, a marine biology professor at Australia's James Cook University, said the lava would have little effect on marine life and would eventually harden and create new land, but a large amount of ash would kill anything in the immediate vicinity.

"In the short term, it is very damaging and will have limited, localized effects," Bellwood said, noting that the ash could kill reefs and marine animals alike. "But an underwater eruption is really a wonderful thing, it's creating new land. This kind of activity helps develop reef systems and preserve marine life."

The quake struck about 200 kilometers south-southeast of the capital, Nuku'Alofa, at a depth of 10 kilometers, the U.S. Geological Survey said.

The agency recorded a 5.3-magnitude aftershock in the same region two hours after the initial quake.

Officials in the Tongan capital, Nuku'alofa, were relieved that the 170-island archipelago appeared to have suffered no injuries or damage.

"Quite remarkable, given the magnitude of it. We might have gotten off lightly," national police commander Chris Kelly said.

"The house really moved. The trees were swaying and the ground was rippling," he said.

Local resident Dana Stephenson said the quake started with "deep rumblings ... then side-to-side movements which seemed to go on forever, but I guess was about 40 seconds - which is long enough."

Radio stations in Tonga broadcast warnings that people should move away from coastal villages due to the tsunami threat that Kelly said was later canceled.

New Zealand seismologist Craig Miller said "a long, low rolling motion" from the quake was reported by residents on the east coast of New Zealand's North Island.

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