Scientists Observe Rapid Change In Underwater Volcano
May 14, 2012

Scientists Observe Rapid Change In Underwater Volcano

Lee Rannals for

Researchers have been able to capture the rise and collapse of an underwater volcano in the Pacific Ocean for the first time.

The team studying Monowai volcano near Tonga has recorded large changes in height of the volcano in just two weeks.

The researchers gathered images by sonar on a ship, unveiling new details about the submarine mountains.

There are as many as 32,000 underwater mountains that have been identified around the world, and the majority of the volcanoes are believed to be volcanic in origin.  Several thousand of these volcanoes could be active, but are too deep and remote for scientists to study.

The new Monowai volcano research helps to provide new insight into the world of submarine geology.  The volcano was first spotted from an aircraft in 1944, and surveys over the years that followed helped reveal significant changes.

Scientists performed studies between 1978 and 2007, and showed Monowai's summit has repeatedly risen and fallen over the years.

However, the most recent analysis of images taken over a few weeks last year reveal that even in a short period, the volcano had transformed.

The scientists first spotted that the sea above the volcano had turned a yellowy-green and gas bubbles were rising to the surface.

"I had butterflies," Tony Watts of Oxford University and lead author of the paper published in the journal Nature Geoscience told the BBC. "The gas was smelling awful - like rotten eggs. We saw a slick ahead of us and with something venting, there could have been a sudden shallowing of the water."

The team left the region and was later warned that seismic detectors on the Cook Islands had detected violent activity around the volcano.

"If we had been over the volcano during the eruption, rocks could have hit the hull of the ship - that could have been potentially dangerous," he told the British news agency.

The researchers returned later and were surprised to see how much the volcano had changed after the eruption.  The volcano's summit had dropped by about 62-feet, and new lava flows has raised another the area another 260-feet.

The authors wrote that only Vesuvius and Mount St Helens had recorded larger growth rates.  They said the speed of growth and change is "a reminder of how rapidly geological processes like submarine land sliding and volcanism can occur."

"Any movement on the seabed has the potential to create a tsunami," Watts told BBC. "An earthquake suddenly dislocates the seabed. Here a violent disturbance lasted five days with magma oozing out which might be too slow to trigger a tsunami - but it's unknown.

"This is a violent exchange of rock into the water - it could destabilize the cone and cause a landslide which in principle could cause a tsunami.

The researchers believe that in order to account for Monowai's growth between 2007 and 2011, the volcano would have needed 10 to 13 events like the one the team witnessed.

"Terrestrial volcanologists get very excited when they see differences of 10 or 20 centimeters," Watts told MSNBC. "What we've seen here is on a scale that has rarely – if ever – been repeated."