Images show how trench swallows volcanoes

MICHELLE COOKE
Last updated 09:57 07/12/2011
Volcano on Tonga Trench
BBC

MARCH INTO THE ABYSS: A sonar image of a volcano beginning to crumble into the trench. Courtesy Universities of Oxford and Durham and NERC.

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Massive underwater volcanoes are slipping into a highly active fault line in the Pacific Ocean, but scientists are baffled as to what the effects of the phenomenon will be.

Incredible new images reveal how tectonic action is dragging huge volcanoes into the Tonga-Kermadec Trench, a fault line which runs north from New Zealand towards Tonga and Samoa, BBC reported.

There are frequent earthquakes in the area and scientists are struggling to understand whether the destruction of the volcanoes increases the risk of a tsunami - or whether it could create a new fault line.

The images, which were taken on a research expedition last year, show how the earth's crust is moving west, where the Pacific plate collides with the Indo-Australian plate.

The trench is 10.9km deep and the second deepest stretch of seabed in the world. The edge of the trench is dotted with volcanoes.

The images show how the giant volcanoes are moving up to 6 centimetres a year, and are collapsing into the chasm.

There were several theories as to what could result from the crumbling volcanoes.

The volcanoes could potentially block or slow down the subduction process, which is when one plate moves under the other, GNS principal scientist Cornel de Ronde said.

That would cause a new fault line to open up somewhere on the earth's crust, and could lead to more earthquakes, possibly in areas that aren't used to experiencing seismic activity.

The scientists on the study first thought that the phenomenon would cause catastrophic earthquakes, but now believe that earthquakes are less frequent where the volcanoes enter the trench.

"When you see size of these features you'd think they'd cause massive earthquakes and disruption - and that was our starting hypothesis," Professor Tony Watts of Oxford University said.

"But we found that the volcanoes were highly fractured before they entered the trench - which is very important for what happens after they enter the system."

Scientists at Oxford and Durham universities were working to determine what the impact of the process would be.

"Are they added to the Australian plate or are they carried down in fragments into the deep earth mantle?," Watts said.

That is the question scientists are trying to answer.

The pictures were created by sonar imaging taken in waters up to 6 kilometres deep.

One image shows that the volcano nearest to the chasm was already starting to collapse.

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