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Undersea Volcano Gave off Signals Before

Eruption in 2011

Photo Courtesy: Hatfield Marine Science Center

A team of scientists that last year created waves by

correctly forecasting the 2011 eruption of

AxialSeamount years in advance now says that the

undersea volcano located some 250 miles off the

Oregon coast gave off clear signals just hours before

its impending eruption.

The researchers documentation of inflation of the

undersea volcano from gradual magma intrusion over a

period of years led to the long-term eruption forecast.

But new analyses using data from underwater

hydrophones also show an abrupt spike in seismic

energy about 2.6 hours before the eruption started,

which the scientists say could lead to short-term

forecasting of undersea volcanoes in the future.

They also say that Axial could erupt again as soon as 2018 based on the cyclic pattern of ground deformation

measurements from bottom pressure recorders.

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Results of the research, which was funded by the National Science Foundation, the National Oceanic and

Atmospheric Administration, and the Monterey Bay Aquarium Research Institute (MBARI), are being published this

week in three separate articles in the journal Nature Geoscience.

Bill Chadwick, an Oregon State University geologist and lead author on one of the papers, said 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

States Hatfield Marine Science Center in Newport, Ore. Weve 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.

Bob Dziak, an Oregon State University marine geologist, had previously deployed hydrophones on Axial that monitor

sound waves for seismic activity. During a four-year period prior to the 2011 eruption, there was a gradual buildup in

the number of small earthquakes (roughly magnitude 2.0), but little increase in the overall seismic energy resulting

from those earthquakes.

That began to change a few hours before the April 6, 2011, eruption, said Dziak, who also is lead author on one of

the Nature Geoscience articles.

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, Dziak 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 isnt yet clear but it gives scientists an excellent base from which to begin.

The researchers also used a one-of-a-kind robotic submersible to bounce sound waves off the seafloor from an

altitude of 50 meters, mapping the topography of Axial Seamount both before and after the 2011 eruption at a one-

meter horizontal resolution. These before-and-after surveys allowed geologists to clearly distinguish the 2011 lava

flows from the many previous flows in the area.

MBARI researchers used three kinds of sonar to map the seafloor around Axial, and the detailed images show lava

flows as thin as eight inches, and as thick as 450 feet.

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.

The researchers also used shipboard sonar data to map a second, thicker lava flow about 30 kilometers south of the

main flow also a likely result of the 2011 eruption.

Knowing the events leading up to the eruption and the extent of the lava flows is important because over the next

few years researchers will be installing many new instruments and underwater cables around Axial Seamount as part

of the Ocean Observatories Initiative. These new instruments will greatly increase scientists ability to monitor the

ocean and seafloor off of the Pacific Northwest.

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 OSUs 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.


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The scientists also observed and documented newly formed hydrothermal vents with associated biological activity,

Chadwick said.

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.

Scientists from Columbia University, the University of Washington, North Carolina State University, and the Universityof California at Santa Cruz also participated in the project and were co-authors on the Nature Geoscience articles.

About OSU's Hatfield Marine Science Center:

The center is a research and teaching facility located in Newport, Ore., on the Yaquina Bay estuary, about one mile

from the open waters of the Pacific Ocean. It plays an integral role in programs of marine and estuarine research and

instruction, as a laboratory serving resident scientists, as a base for far-ranging oceanographic studies and as a

classroom for students.


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