Deepest Underwater Volcanic Eruption Discovered

It is about 14,700 feet (4,500 meters), or 2.8 miles, below the ocean surface, making it the deepest known eruption on Earth.  (Image: via   Oregon State University  )
It is about 14,700 feet (4,500 meters), or 2.8 miles, below the ocean surface, making it the deepest known eruption on Earth. (Image: via Oregon State University )

A team of researchers has documented a recent volcanic eruption on the Mariana back-arc in the western Pacific Ocean that is about 14,700 feet (4,500 meters), or 2.8 miles, below the ocean surface, making it the deepest known eruption on Earth. That is deeper below the ocean surface than Mount Rainier’s height above sea level.

It was discovered by researchers searching for new hydrothermal vent sites where the Pacific tectonic plate subducts beneath the Philippine Sea plate, forming the Mariana trench and the active volcano arc, which is made up of nine islands and more than 60 seamounts. The Mariana back-arc is a zone of seafloor spreading and active volcanism in the upper plate behind the volcanic arc.

Fresh lava. (Image: via Oregon State University )

Fresh lava. (Image: via Oregon State University )

The research is published in a special issue of Frontiers in Earth Science. Bill Chadwick, a marine geologist at Oregon State University and NOAA’s Pacific Marine Environmental Laboratory, who is lead author on the study, said:

Chadwick said that in the last 30 years, scientists utilizing improving technology and exploration methods have detected evidence of about 40 undersea eruptions. Before 1990, he said, there were zero. The Mariana back-arc eruption was first discovered in December 2015 by cameras aboard an autonomous underwater vehicle, Sentry.

Photos revealed the presence of a pristine dark, glassy lava flow on the seafloor with no sediment cover. Venting of milky hydrothermal vent fluid indicated that the lava flow was still warm, and therefore very young. Newly collected bathymetric data indicated major depth changes in the area between surveys in 2013 and 2015, consistent with an eruption. The new lava flows stretched over an area about 4.5 miles long and ranged in thickness between 130 and 450 feet.

Squat lobster. (Image: via Oregon State University )

Squat lobster. (Image: via Oregon State University )

The scientists returned to the site in April and December of 2016 and used remotely operated vehicles Deep Discoverer and SuBastian during expeditions on the NOAA ship Okeanos Explorer and the research vessel Falkor. The new observations showed a rapidly declining hydrothermal system on the lava flows, suggesting the eruption had taken place only months before its discovery the previous year. Chadwick said:

Chadwick was part of science teams that actually observed underwater eruptions at NW Rota Seamount along the Mariana volcanic arc. He and his colleagues have also monitored Axial Seamount off the Pacific Northwest coast of the United States and documented three eruptions there in the last 20 years, and monitoring data shows that it is building toward another eruption within the next several years.

The research is important, he says, for several reasons. Chadwick, who works at OSU’s Hatfield Marine Science Center in Newport, Oregon, noted:

Provided by: Oregon State University [Note: Materials may be edited for content and length.]

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