Published on June 11th, 2012 | by James Ayre0
Underwater Volcano Gave Clear Signals Before Eruption
June 11th, 2012 by James Ayre
An undersea volcano located 250 miles off the coast of Oregon gave off clear warning signals just hours before erupting last year, according to researchers from Oregon State University.
The research is from the same team that correctly predicted the eruption of the same volcano, years in advance, before its 2011 eruption.
The researchers had predicted the 2011 eruption by documenting the levels of magma intrusion and the volcano’s inflation.
By reanalyzing their original underwater hydrophones data, the researchers have found an abrupt spike in seismic energy about 2.6 hours before the eruption. The researchers think this discovery may lead to short-term underwater volcanic prediction.
The researchers also think the volcano, Mount Axial, may erupt again as soon as 2018. This is based on “the cyclic pattern of ground deformation measurements from bottom pressure recorders.”
The lead author and an Oregon State Geologist, Bill Chadwick, said that “the link between seismicity, seafloor deformation and the intrusion of magma has never been demonstrated at a submarine volcano, and the multiple methods of observation provide fascinating new insights.”
“Axial Seamount is unique in that it is one of the few places in the world where a long-term monitoring record exists at an undersea volcano – and we can now make sense of its patterns,” said Chadwick, who works out of Oregon State’s Hatfield Marine Science Center in Newport, Ore. “We’ve been studying the site for years and the uplift of the seafloor has been gradual and steady beginning in about 2000, two years after it last erupted.”
“But the rate of inflation from magma went from gradual to rapid about 4-5 months before the eruption,” added Chadwick. “It expanded at roughly triple the rate, giving a clue that the next eruption was coming.”
In the four months before the eruption, hydrophones at the volcano had recorded a gradual buildup in the number of small earthquakes, but not much increase in the overall seismic energy being released. A few hours before the eruption, though, that began to change.
“The hydrophones picked up the signal of literally thousands of small earthquakes within a few minutes, which we traced to magma rising from within the volcano and breaking through the crust,” Bob Dziak, an Oregon State Biologists said. “As the magma ascends, it forces its way through cracks and creates a burst of earthquake activity that intensifies as it gets closer to the surface.”
“Using seismic analysis, we were able to clearly see how the magma ascends within the volcano about two hours before the eruption,” Dziak said. “Whether the seismic energy signal preceding the eruption is unique to Axial or may be replicated at other volcanoes isn’t yet clear – but it gives scientists an excellent base from which to begin.”
The researchers also used a robotic submersible to bounce sound-waves off the seafloor, mapping the terrain before and after the eruption. These before and after maps allow the researchers to distinguish new lava flows.
The researchers also used three different kinds of sonar to map the seafloor around Mount Axial, finding larva flows up to 450 feet thick.
“These autonomous underwater vehicle-generated maps allowed us, for the first time, to comprehensively map the thickness and extent of lava flows from a deep-ocean submarine in high resolution,” said David Caress, an MBARI engineer and lead author on one of the Nature Geoscience articles. “These new observations allow us to unambiguously differentiate between old and new lava flows, locate fissures from which these flows emerged, and identify fine-scale features formed as the lava flowed and cooled.”
In the next few years, the researchers will be “installing many new instruments and underwater cables around Axial Seamount as part of the Ocean Observatories Initiative.” These will greatly increase monitoring capacity at the volcano.
“Now that we know some of the long-term and short-term signals that precede eruptions at Axial, we can monitor the seamount for accelerated seismicity and inflation,” said OSU’s Dziak. “The entire suite of instruments will be deployed as part of the Ocean Observatories Initiative in the next few years – including new sensors, samplers and cameras – and next time they will be able to catch the volcano in the act.”
The researchers also found new hydrothermal vents after the eruption, and biological activity gathering at them.
“We saw snowblower vents that were spewing out nutrients so fast that the microbes were going crazy,” he pointed out. “Combining these biological observations with our knowledge of the ground deformation, seismicity and lava distribution from the 2011 eruption will further help us connect underwater volcanic activity with the life it supports.”
Source and Images: Oregon State University
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