Undersea Volcano Erupts a Mile Below the Surface

It’s sort of a variation on the old “If a tree falls in a forest…” quandary. 80 percent of volcanic eruptions on Earth probably go unnoticed by people, because they take place in the planet’s oceans, often at depths of thousands of feet. There’s nobody down there to flee in terror or to write an eloquent account of nature’s fury, as Pliny the Younger did when Vesuvius erupted back in 79 AD.

Or rather, undersea eruptions used to go unnoticed. University of Washington researchers have installed an array of cutting-edge monitoring instruments in the vicinity of the Axial Seamount, an underwater volcanic mountain that’s about 300 miles off the coast of the Pacific and a mile beneath the ocean surface. In late April, that gadgetry enabled them to anticipate and then observe a eruption in real time, and to collect a massive amount of data on the event.

“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,” noted UW oceanography professor John Delaney in a press release.

The researchers, who are working in a larger effort sponsored by the National Science Foundation, got their first inkling that Axial was about to blow just before midnight on April 23, when eight seismometers installed at the site transmitted warnings that seismic activity in that area was going off the charts. The rate of tremors increased dramatically over the next 12 hours, to a rate of thousands per day.

Meanwhile, the center of Axial’s volcanic crater dropped by about 6 feet.

“The only way that could have happened was to have the magma move from beneath the caldera (the collapse of land following an eruption) to some other location,” Delaney said, “which the earthquakes indicate is right along the edge of the caldera on the east side.”

Axial Seamount’s latest eruption actually was predicted in advance by Oregon State University researcher Bill Chadwick and his colleague Scott Nooner at the University of North Carolina at Wilmington. It previously erupted in 1998 and 2011, when scientists captured a picture of a bizarre layer of undersea glass formed when molten lava from the volcano encountered the near-freezing seawater.

From Discovery News