Rota’s undersea volcano shows nonstop eruption

A team of scientists returned this month with new and dramatic video and sound recordings of an ongoing volcanic eruption underneath the deceptively calm waters of Rota Island in the Northern Mariana Islands.

Video of billowing ash plumes, molten sulfur droplets, and red lava jetting from a vent are just some of the new materials that the NOAA-led team of ocean explorers have of this long-term deep-sea volcanic eruption that was first discovered in 2004.

The eruption is at Brimstone Pit, a vent high on the side of the large submarine volcano called NW Rota-1, located about 37 miles northwest of the island of Rota, in the Northern Mariana Islands.

The volcano is one of many on the Mariana Arc, part of the “Submarine Ring of Fire” that circles the Pacific Ocean basin, where tectonic plates spread or collide.

“In three international expeditions spanning more than two years, we’ve discovered a submarine volcano erupting perhaps continuously and often violently, spewing rocks that sometimes forced us to back away our remotely operated vehicles,” said Bob Embley, an oceanographer with the NOAA Pacific Marine Environmental Laboratory in Newport, Ore., and chief scientist on missions in 2004 and 2006. “But with those underwater robots, we could often get in close to take compelling images and to sample the chemistry in ways not possible with volcanoes on land.”

The 2006 Submarine Ring of Fire expedition from April 18 to May 13, 2006, is the third in a series of explorations of the submarine volcanoes lying along the Mariana Arc, extending from south of the island of Guam northward more than 800 nautical miles (1,450 km).

Third expedition

A paper in the May 25 issue of the science journal Nature, with Embley as lead author, reports findings from the NOAA-sponsored expedition to the site in 2004, and from an expedition in 2005 sponsored by the Japanese Agency for Marine-Earth Science and Technology, and led by JAMSTEC’s Yoshihiko Tamura. The paper presents the first observations of a deep-sea eruption on a submarine arc volcano and its effects on the surrounding ocean, and describes plumes of sulfur-rich fluids and volcanic ash expelled in pulses from a crater that in 2004 measured nearly 50 feet in diameter at a depth of about 1,800 feet.

This year’s NOAA-sponsored mission was composed of an interdisciplinary team of 21 scientists from the U.S., Japan, Canada and New Zealand that sailed on the research vessel Melville, operated by the Scripps Institution of Oceanography. The science team worked closely with the Deep Submergence Operations Group of Woods Hole Oceanographic Institution to use the remotely operated vehicle Jason II to explore and collect samples on nine different active submarine volcanoes.

Bill Chadwick, a geologist at Oregon State University and the NOAA Vents Program, was on the 2004 and 2006 expeditions.

“The eruptive activity at Brimstone Pit, although violent at times, is usually limited to a small area because of the dampening effect of the surrounding water,” he said.

“The pressure of 1,837 feet of water over the site reduces the power of the explosive bursts, and the water quickly slows down the rocks and ash that are violently thrown out of the vent. Most of the time, the underwater robot Jason could hover about 10 feet away and watch for hours. You could never do that on land,” he said. “We could also see the release of volcanic gases from the erupting lava with new clarity with the help of the streams of bubbles and multicolored plumes as they were emitted.”

“Locally, carbon dioxide forms waterfalls of bubbles in front of the advancing lava,” said Cornel de Ronde, a geologist with New Zealand’s Institute of Geological & Nuclear Sciences, when describing Brimstone Pit. “It is these different gases that are the force behind the vigorous ‘mini-explosions’ within the lava flow.”

Life in the extreme

The scientists have also observed communities of microscopic bacteria and two species of shrimp living at the volcano.

The bacteria settle around vents that spew out hydrogen sulfide, a chemical that the life-forms convert into food, says Verena Tunnicliffe, a marine biologist at the University of Victoria in British Columbia, Canada.

“On NW Rota, not many animals would want to live on an erupting volcano, but two feisty shrimp species are able to reap the benefits of the volcano’s hydrothermal activity where heated fluids are full of reduced chemicals that foster the growth of bacteria. Bacterial mats coat many rock and rubble surfaces thus forming an abundant food source for animals that can use such mats,” she said. “So that means there’s an OK food source sitting there if you’re able to live in an unstable, nasty place.”

At Daikoku Volcano on the northern part of the Mariana Arc chain, researchers found a pool of liquid sulfur at a depth of 1,365 feet with a “crust” moving in a wavelike motion from continuous flow of gas from below. Liquid sulfur and clouds of gases rich in hydrogen sulfide and other sulfur gases, could be linked to an unusually high density of chemosynthetic organisms found on Mariana submarine volcanoes.

“These expeditions are part of our mission to explore the ocean for the purpose of discovery and the advancement of knowledge,” said Steve Hammond, acting director of the NOAA Office of Ocean Exploration. “They are critically important pathfinding missions that challenge us to understand the fundamental processes of the ocean and how they affect our lives.” (NOAA)