Undersea image of Axial Seamont.

Undersea image of Axial Seamont.

Oregon State University

An underwater volcano, some 300 miles off the Oregon Coast, is providing clues about how to better understand — and predict — eruptions.

The seamount erupted in 1998, 2011 and 2015.

Researchers from Oregon State University, NOAA’s Pacific Marine Environmental Laboratory, and the University of North Carolina found that after each eruption, the seafloor dropped by about eight feet and then gradually rose back up again over several years.

OSU Volcanologist William Chadwick says the underwater volcano can be thought of as a balloon, except it inflates and deflates with magma instead of air.

Three new papers were published this week about the volcano, including how the inflation movements helped researchers forecast the 2015 eruption seven months in advance.

Chadwick says seismic imaging works better in water.

On land, researchers have to drill holes, set off explosions, and record them with a few scattered seismometers.  But when the volcano is underwater, a ship can float over it, easily gathering data.