Extremes of Eel City
|Hydrothermal vents provide fuel for life on the seafloor. Credit: lostcity.washington.edu|
An international team of scientists, led by researchers at the Woods Hole Oceanographic Institution, Scripps Institution of Oceanography, University of Oregon and University of Sydney, has discovered an active underwater volcano near the Samoan Island chain about 2,400 miles southwest of Hawaii.
During a research cruise to study the Samoan hot spot, scientists uncovered a submarine volcano growing in the summit crater of another larger underwater volcano, Vailulu’u. Researchers explored the unique biological community surrounding the eruption site, and were amazed to find an ‘Eel City,’ a community of hundreds of eels.
This new volcano, dubbed Nafanua after the ferocious Samoan goddess of war, did not exist just fours years ago, according to co-chief scientists Stan Hart, a geochemist at Woods Hole Oceanographic Institution (WHOI), and Hubert Staudigel, a geologist at Scripps Institution of Oceanography. With a growth rate averaging eight inches per day, the volcanic cone has rapidly formed since the scientists’ last expedition to this area in May 2001. Nafanua now stands at 300 meters, or nearly 1,000 feet.
"To actually have a documented case of an underwater volcano that has been constructed within a known period of time is very rare–this is one of those cases," said Hart, a Senior Scientist in the WHOI Geology and Geophysics Department.
Scientists were tipped off to the volcano’s existence when they profiled the seafloor of the Vailulu’u crater using multi-beam mapping. Existing maps of the seafloor in the area gave little indication that this volcano existed. When sound beams were directed into the crater this time, they measured an unusually shallow depth. These interesting results prompted further investigation of the area using the manned submersible Pisces V–a seven-foot sphere that can dive to more than 6,000 feet, operated by NOAA’s Hawaii Undersea Research Laboratory.
The water surrounding the volcanic cone is extremely turbid due to hydrothermal activity and the vigorous vents that produce this volcanic ‘fog’ are obscured, according to Staudigel. Although visibility from the submersible was less than 10 feet, the researchers were able to observe the unique biological community surrounding the newly formed volcanic cone.
Much of Nafanua is covered with yellow ‘fluff,’ microbial aggregations that are produced by microscopic life feeding on chemical energy from the volcano’s hydrothermal system.
As this international team explored the area, they discovered a number of large communities of eels inhabiting the fragile cavernous rock pillars surrounding the hydrothermal vent area. As the submarine landed near this area, scores of eels, each approximately one foot long, emerged from the rock caves and crevices. The scientists named this novel marine hydrothermal community ‘Eel City.’
"At this point we do not know why we found such extensive eel communities surrounding this volcano–it’s a mystery that we hope to learn more about on future cruises," Staudigel said.
Within decades, continued growth of Nafanua could bring the summit of this volcano from its current depth of 600 meters to a depth of approximately 200 meters–close enough to the sea surface that it could provide a potential hazard to ocean navigation and coastal communities. Such hazards may include the explosive reaction between red-hot lava and seawater, or tsunamis that may be caused by the collapse of the newly built volcano.
"It is a good idea for us to keep our eyes on this area, but there is no real reason for concern about immediate danger," said Hart.
Three students from High Tech High in San Diego were aboard one of the two expeditions to Nafanua and assisted researchers in collecting and analyzing data. These students also created and maintained an in-depth Web site related to the cruise where they posted reports, maps, photos and videos from submersible dives. Also, the students and scientists aboard the ship participated in the first ever student-to-student videoconference between a high school and a research vessel with the help of HiSeasNet, a satellite communications system that provides continuous Internet connectivity for oceanographic research vessels at sea.
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