Most volcanic eruptions on Earth happen in a hidden, dark place: deep underwater. Scientists rarely detect these outbursts on the sea floor, but last year, they caught a seamount eruption in the act. Now, researchers have characterized it in unprecedented detail—showing how a rash of earthquakes preceded the eruption and how bulging of the volcano’s surface was used to successfully forecast the eruption. Scientists say the results will help them understand how other volcanoes around the world behave.
(From Science Magazine / by Julia Rosen)– The eruption began on 24 April 2015 at Axial Seamount, which lies 480 kilometers off the Oregon coast. Researchers already had a good picture of the volcano’s magma chamber, and they’ve now learned how it erupts, thanks to a cabled array of seismometers and pressure gauges deployed by the U.S. Ocean Observatories Initiative (OOI) and other projects. Scientists hope the results, published today in two Science papers, will shed light on volcanic processes, and also help quiet the OOI’s detractors, who have criticized the project’s $1.8 billion lifetime cost.
Immediately after the OOI sensors came online in late 2014, they started recording hundreds of daily tremors, says William Wilcock, a marine geophysicist at the University of Washington in Seattle who led the first study. By March 2015, they had increased to upward of 2000 per day. The frequency of earthquakes also tracked the tides, with more than six times as many events occurring at low tide—a pattern that can be a sign of an imminent eruption, Wilcock says. If the volcano is close to erupting, pressure from the magma critically stresses the faults, so that a drop in water pressure at low tides can trigger small earthquakes. “You unclamp the faults,” he says. After the eruption, seismometers also recorded booms that the researchers attribute to steam exploding out of fresh rock, which helped them map lava flows.
The eruption didn’t come out of the blue, however. Scientists had some pressure recorders, which measure seafloor deformation, in place for eruptions in 1998 and 2011. Based on how fast magma seemed to be accumulating again in recent years, lifting the roof of the volcanic caldera, researchers were expecting another outburst soon. “The magma chamber inflates to a certain level, and then it can no longer withstand the pressure anymore and the magma breaks out,” says Scott Nooner, a geophysicist at the University of North Carolina in Wilmington.
In September 2014, after seeing that the caldera had started growing at a faster rate, Nooner and William Chadwick, a geologist at the Hatfield Marine Science Center in Newport, Oregon, predicted another eruption in 2015. In the second study, they show that their forecast was successful. The researchers also documented how the caldera deflated by 2.5 meters after the lava erupted.
Read the full article here: http://www.sciencemag.org/news/2016/12/underwater-network-gives-scientists-rare-glimpse-deep-sea-volcanoes