Shake, Rattle and…

06.20.2012 |

Axial Seamount. Image from USGS.

Let’s start by stating the obvious:  being able to predict volcanic eruptions is good.  But not every volcano is going to cause destruction on the scale of Mt. St. Helens or Eyjafjallajokull (say that 3 times fast).  Some volcanoes – like the ones located underneath the sea –can erupt without human beings even noticing.

That’s not to say that these eruptions aren’t destructive.  They can wipe out the surrounding seafloor ecosystems. That’s one reason scientists are interested in trying to predict these undersea eruptions; another reason is that every such eruption can give us more information about the movement of tectonic plates.

While undersea volcanic eruptions can give us valuable data, predicting when they might erupt has traditionally been a bit difficult. So when an undersea volcano known as Axial Seamount became active in the early 2000s, researchers figured they had a great candidate for testing some theories about predicting undersea eruptions.

Axial Seamount is located on the Juan de Fuca Ridge, about 200 miles off the coast of Oregon and Washington State. “It’s a really neat area – a ‘hot spot’ for volcanic activity, like Hawaii, and a place where the tectonic plates are slowly moving apart, so there’s a lot of seismic activity,” says Del Bohnenstiehl, associate professor of marine, earth and atmospheric sciences.  “However, nearly all of the earthquakes are too small to be detected using the existing network of seismic stations on land.”

In 2007, Bohnenstiehl joined a team of researchers from Oregon State and NOAA to monitor the Axial Seamount volcano. They created undersea seismometers by attaching hydrophones (which measure underwater sound waves) to metal plates and placing them on the volcano’s surface.  They also utilized bottom pressure recorders, which measure the displacement of the earth on a volcano. Then they waited.

Four years later, they recorded an eruption. And more importantly, they had data that showed a regular, measurable increase in seismic activity leading up to the eruption – a key to predicting volcanic behavior.

“Seismic activity increased in the years leading up to the eruption, but right before it began we saw a really sharp seismic increase,” Bohnenstiehl says. “There was a two-to-three hour window between this increase and the start of the eruption, which means that using real-time seismic data could give researchers enough lead time before an eruption to be able to gather valuable data about these events.”



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