Tuesday, November 14, 2006

Island born from volcano eruption

Tonga's chief geologist said Tuesday he hopes to visit a neighboring island that recently rose from the Pacific Ocean during a recent undersea volcanic eruption, before waves erode it.

Government geologist Kelepi Mafi said he plans to visit the chunk of rock next week if his country can afford to send a military ship there.

Satellite images and passing sailors' reports suggest a new piece of land emerged from the ocean near the northern Tongan island group of Vava'u in early August.

Mafi said no officials had yet been to the site, where yacht crews described an active volcanic island 1.6 kilometers (1 mile) in diameter, with four peaks and a central crater.

Earthquake readings indicate that a "pretty sizable" event had occurred in the area, and photos show a new land mass that is "quite large," Mafi said by telephone from Tonga's capital, Nuku'alofa.

"We are still studying the seismogram ... but we want to send a team to the site itself and look at the eruption," he said.

He hopes that if funding is available, a Tongan Defense Service boat will take a party to the island next week.

The crew of the Maiken, a yacht that left Vava'u in early August, reported on their Web log on Aug. 12 that they saw "rafts" of light, porous pumice stone floating in the water — then spotted the active volcano.

They also posted photos of huge pumice rafts that they encountered after passing Tonga's Late island while sailing toward Fiji.

Mafi said one of Nuku'alofa's eastern beaches also had been "flooded" with black pumice shortly after the eruption.

Ed Venzke, an editor with the Smithsonian Institution's Bulletin of the Global Volcanism Network, said first reports of the new island had come from passing boats, and he has since confirmed its existence from satellite images.

The same volcano last erupted in 1984, producing an island that has since eroded away.
"It looks like there was a similar type of eruption. It has built up a new island and produced huge amounts of pumice," Venzke told The Associated Press by phone from Washington.

He said an Oct. 4 satellite image showed the island was 0.098 square acres (0.04 hectares) in area.

"If it's just pumice that has built up the island, the waves will knock it down and erode it very quickly. It won't last long," he said.

It was not yet known whether the eruption was continuing, or if there is any lava flow.

"But if this eruption continues and produces lava flows, the lava flows will cool and form a hardened shell on the island that will be more resistant to being eroded away," Venzke said.

Volcanoes that produce such eruptions are remote, so little is known about them.

"There are many cases in the past where we received reports of pumice rafts, but had no idea of where the rafts came from," Venzke said.

Richard Wunderman, editor of the Washington-based Bulletin of the Global Volcanism Network, said a large pumice raft, presumably from Tonga, has been sweeping across Fiji, and they were trying to learn about its origins.

A previous eruption in the area generated a small island and similar fields of floating pumice, he said.

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