Undersea volcano may provide clues to terrestrial eruptions

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Undersea volcano may provide clues to terrestrial eruptions
A deep sea octobus explores the new lava flows on Axial Seamount in 2015.

The Axial Seamount, located some 300 miles off the Oregon Coast, has become one of the most intensely studied volcanoes on Earth – and it may provide clues to better understand how and when terrestrial volcanoes erupt.

Three new papers published this week detail the workings of the most active undersea volcano in the northeast Pacific Ocean, which erupted in 1998, 2011 and 2015 – the latter of which was forecast seven months in advance by researchers from Oregon State University, NOAA’s Pacific Marine Environmental Laboratory, and the University of North Carolina at Wilmington.

The key to the researchers’ forecast was a gradual inflation of the seafloor created by intruding magma, noted William Chadwick, an Oregon State volcanologist and co-author on two of the three papers, which are being published in Science and Geophysical Research Letters. Chadwick also is with NOAA’s Pacific Marine Environmental Laboratory.

“We’re beginning to really understand how this volcano works and some of these lessons can be applied to other volcanoes in a general way,” Chadwick said.

“During its eruptions, Axial’s seafloor drops suddenly by about eight feet, and then over the next several years it gradually rises back up. When it re-inflates to a certain level, the volcano is almost ready to erupt again.

“Axial inflates and deflates like a balloon, except it’s filling with magma instead of air.”

Chadwick said that following the 2015 eruption, Axial began re-inflating rapidly at first but the rate has been slowing. The volcano has regained just less than half of the eight feet of seafloor it lost during the 2015 eruption.

“Now we’ll just have to watch and see how fast it builds back up,” Chadwick said. “We’ll be trying to forecast the next eruption again, but right now it’s a little too early to tell.”

Chadwick calls Axial Seamount a “great natural laboratory” because it is close to land, has a simple structure and is frequently active, yet not a hazard to people.

“Ironically, in some ways we can learn more about how volcanoes work by studying them underwater because the seismic imaging works so much better in the oceans,” Chadwick said.

“Previous surveys created the images of where the magma is and because ships can go everywhere over the volcano we get a lot more data. On land, you have to drill a hole, set off an explosion, and record it with a few scattered seismometers. It’s not nearly as effective.”

That previous seismic data helped the researchers interpret the monitoring data collected during the 2015 eruption.

The researchers also have benefited from the Ocean Observatories Initiative, a National Science Foundation-funded program to study the world’s oceans that includes the Cabled Array, a network of sensors that helped them make real-time seismicity and geodetic measurements.

The instruments recorded a growing number of tiny earthquakes that increased from fewer than 500 a day to more than 2,000. During the eruption, there were 600 earthquakes every hour, according to William Wilcock at the University of Washington.

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News source: Oregon State University.
Figure legend: This Knowridge.com image is credited to Bill Chadwick, Oregon State University, and ROV Jason, Woods Hole Oceanographic Institution.