August 10, 2011

Undersea Volcano Erupts, Just As Predicted

US scientists from Oregon and New York, who have been monitoring the Axial Seamount, an undersea volcano located 250 miles off the Oregon coast, said on Tuesday that they have successfully predicted an eruption for the first time.

The team of scientists forecast the eruption beginning about five years ago, predicting the volcano, which last erupted in 1998, would erupt again sometime before 2014. This marks the first successful prediction of eruption of an undersea volcano.

During an expedition to the site on July 29th, researchers using a remotely operated robot found a lava flow that was not there the year before, and began noticing that the entire area looked very different than before.

"When we first arrived on the seafloor, we thought we were in the wrong place, because it looked so completely different," said Bill Chadwick, an Oregon State University geologist who forecast another eruption by 2014. "We couldn't find our markers or monitoring instruments or other distinctive features on the bottom."

The team was using bottom pressure sensors, the same tools used to monitor the sea floor for potential tsunamis after an earthquake. They were finally able to locate a few of their instruments and then discerned that the eruption occurred on April 6 of this year.

Scott Nooner, of Columbia University, has been monitoring Axial Seamount for more than a decade along with Chadwick. Their 2006 paper, published in the Journal of Volcanology and Geothermal Research, predicted that Axial would erupt before the year 2014. Their forecast was based on a series of seafloor pressure measurements that indicated the volcano was inflating.

"Volcanoes are notoriously difficult to forecast and much less is known about undersea volcanoes than those on land, so the ability to monitor Axial Seamount, and determine that it was on a path toward an impending eruption is pretty exciting," said Chadwick, who was chief scientist on the recent expedition, which was jointly funded by the National Oceanic and Atmospheric Administration and the National Science Foundation.

Axial last erupted in 1998 and Chadwick, Nooner and their colleagues have been monitoring it ever since. "It is now the only volcano on the seafloor whose surface deformation has been continuously monitored throughout an entire eruption cycle," added Nooner.

The bottom pressure sensors measure vertical movements of the floor of the caldera much like scientists would use GPS on land to measure movements of the ground. They discovered that the volcano was gradually inflating at the rate of six inches per year, indicating that magma was rising and accumulating under the volcano's summit.

When Axial last erupted, the floor of the caldera suddenly subsided by 10.5 feet as magma was removed from the underground chamber to erupt at the surface. The scientists estimated that Axial would erupt again when re-inflation pushed the caldera floor back up to its 1998 level.

"So far, it is hard to tell the full scope of the eruption because we discovered it near the end of the expedition," said Chadwick, who works out of OSU's Hatfield Marine Science Center in Newport. "But it looks like it might be at least three times bigger than the 1998 eruption."

The scientists noted that the lava flow from the 2001 eruptions was at least 1.2 miles wide.

Axial Seamount's eruption "has resulted in millions of square meters of new lava flows on the seafloor," said Barbara Ransom, program director in the National Science Foundation's Division of Ocean Sciences. "The technological advances that allow this research to happen will lead to a new understanding of submarine volcanoes, and of any related hazards."

The bottom-anchored instruments documented hundreds of tiny earthquakes during the volcanic eruption, but land-based seismic monitors and the Sound Surveillance System (SOSUS) hydrophone array operated by the U.S. Navy only detected a handful of them on the day of the eruption because many components of the hydrophone system are offline.

"Because the earthquakes detected back in April at a distance from the volcano were so few and relatively small, we did not believe there was an eruption," Bob Dziak, an OSU marine geologist who monitors the SOSUS array, told AFP. "That is why discovering the eruption at sea last week was such a surprise."

Both Dziak and Chadwick are affiliated with the Cooperative Institute for Marine Resource Studies "“ a joint NOAA/Oregon State University institute.

"The acid test in science "“ whether or not you understand a process in nature "“ is to try to predict what will happen based on your observations," Chadwick said. "We have done this and it is extremely satisfying that we were successful. Now we can build on that knowledge and look to apply it to other undersea volcanoes "“ and perhaps even volcanoes on land."

The scientists will now work with Julie Huber of the Marine Biological Laboratory in Woods Hole, Massachusetts to analyze DNA and RNA of microbes found in samples from the surrounding area of the undersea volcano.


Image 1: The manipulator arm of the ROV Jason prepares to sample the new lava flow that erupted in April 2011 at Axial Seamount, located off the Oregon coast. (photo courtesy of Bill Chadwick, Oregon State University; copyright Woods Hole Oceanographic Institution)

Image 2: A spider crab inspects an ocean-bottom hydrophone mooring at the Axial Seamount before its 2011 eruption. The hydrophone, in the white pressure case, is designed to detect undersea earthquakes. (photo courtesy of Bill Chadwick and Bob Dziak of Oregon State University, copyright Woods Hole Oceanographic Institution)


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