If a volcano erupts at the bottom of the sea, does anybody see it? If
that volcano is Axial Seamount, about 300 miles offshore and 1 mile
deep, the answer is now: yes.
Thanks to a set of high-tech instruments installed last summer by the
University of Washington to bring the deep sea online, what appears to
be an eruption of Axial Volcano on April 23 was observed in real time by
scientists on shore.
"It was an astonishing experience to see the changes taking place 300
miles away with no one anywhere nearby, and the data flowed back to
land at the speed of light through the fiber-optic cable connected to
Pacific City -- and from there, to here on campus by the Internet, in
milliseconds," said John Delaney, a UW professor of oceanography who led
the installation of the instruments as part of a larger effort
sponsored by the National Science Foundation.
This custom-built precise pressure sensor detects the seafloor's rise
and fall as magma, or molten rock, moves in and out of the underlying
magma chamber. Three are installed on the caldera of the underwater
volcano.NSF-OOI/UW/CSSF
Delaney organized a workshop on campus in mid-April at which marine
scientists discussed how this high-tech observatory would support their
science. Then, just before midnight on April 23 until about noon the
next day, the seismic activity went off the charts.
The gradually increasing rumblings of the mountain were documented
over recent weeks by William Wilcock, a UW marine geophysicist who
studies such systems.
During last week's event, the earthquakes increased from hundreds per
day to thousands per day, and the center of the volcanic crater dropped
by about 6 feet (2 meters) over the course of 12 hours.
"The only way that could have happened was to have the magma move
from beneath the caldera to some other location," Delaney said, "which
the earthquakes indicate is right along the edge of the caldera on the
east side."
The seismic activity was recorded by eight seismometers that measure
shaking up to 200 times per second around the caldera and at the base of
the 3,000-foot seamount. The height of the caldera was tracked by the
bottom pressure tilt instrument, which measures the pressure of the
water overhead and then removes the effect of tides and waves to
calculate its position.
The depth instrument was developed by Bill Chadwick, an oceanographer
at Oregon State University and the National Oceanic and Atmospheric
Administration who has also been tracking the activity at Axial Volcano
and predicted that the volcano would erupt in 2015.
The most recent eruptions were in 1998 and 2011.
The volcano is located about 300 miles west of Astoria, Oregon, on
the Juan de Fuca Ridge, part of the globe-girdling mid-ocean ridge
system -- a continuous, 70,000 km (43,500 miles) long submarine volcanic
mountain range stretching around the world like the strings on a
baseball, and where about 70 percent of the planet's volcanic activity
occurs. The highly energetic Axial Seamount, Delaney said, is viewed by
many scientists as being representative of the myriad processes
operating continuously along the powerful subsea volcanic chain that is
present in every ocean.
"This exciting sequence of events documented by the OOI-Cabled Array
at Axial Seamount gives us an entirely new view of how our planet
works," said Richard Murray, division director for ocean sciences at the
National Science Foundation. "Although the OOI-Cabled Array is not yet
fully operational, even with these preliminary observations we can see
how the power of innovative instrumentation has the potential to teach
us new things about volcanism, earthquakes and other vitally important
scientific phenomena."
The full set of instruments in the deep-sea observatory is scheduled
to come online this year. A first maintenance cruise leaves from the UW
in early July, and will let researchers and students further explore the
aftermath of the volcanic activity.
This story is taken from Science Daily
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