bob@uhmanoa.UUCP (Bob Cunningham) (12/10/87)
Getting there is "like swimming in yellow paint". But the surface is red, like Mars. Hovering around one of the active vents is "almost like being in the middle of Niagra Falls, with massive hot waterfalls cascading and shimmering around you," says Alex Malahoff. Then, there the forests of chimneys, populations of weird bacteria, and a few of the world's ugliest fishes. That's what it's like around the top of the Loihi volcano, 4,000' feet below the surface of the Pacific, 21 miles south of the island of Hawaii. Malahoff, Mike Garcia, and other researchers from the University of Hawaii, along with Harmon Craig, Dave Hilton and others of Scripps Institute of Oceanography, first visited Loihi in February using the Woods Hole Oceanographic Institute's submersible Alvin. Last month, Malahoff and others re-visited Loihi using UH's Pisces V submersible, just recently overhauled for Pacific Ocean work. At its summit, Loihi reaches to about 3,000' below the surface, with the whole summit constantly breaking up and leaking lava. Nothing is stable; Loihi appears to be erupting continuously. Two rift zones have been identified so far, on the northern and southern flanks of Loihi. The main vents on the south rift zone (with the most active hydrothermal vents yet found) are about 4,000' deep. There are hundreds, probably thousands of these vents, white orifices, producing hot water with high concentrations of methane, and CO2. The CO2 concentration is about 140 times that of normal sea water. Water (and rock) samples brought to the surface fizzle like a bottle of champagne that has been shaken up before being uncorked. The vent water contains unusual bacteria able to grow without oxygen at temperatures measured up to 75 degrees centrigade, and probably higher, most likely using energy from the methane. Hydrothermal deposits include nontronite, an iron-rich clay (giving the bottom its distinctive reddish color), enriched with some high temperature metals, including gold. A "seep area" downslope from the active hydrothermal fields where water may be seeping out has continuous mats of bacteria-like "lawns", very different from bacteria at other vents (such as mid-ocean ridge vents), and may be unique to Loihi. These bacteria may be using iron from the seepage as an energy source, preserved in iron oxide formed outside their cells. The clams, worms, and other large animals normally associated with hot water vents are not found on Loihi. However, two toad-like fish were captured on the summit back in February---described by several people as "possibly the world's ugliest fishes"---have been identified as members of a rare monkfish species (Sladenia remiger) found only once before, in 1912 in the Philippines. Including the Loihi specimens, only six individual fish in this genus have been caught and recorded (including a Sladenia gardineri, caught in the Chagos Arichpelago in 1908, and several Sladenia schaefersi caught in 1976 in the Carribean)...although similar fish have allegedly been seen at 3,000' off the Kona coast of Hawaii. The exploration of Loihi has just begun, with long-term plans to study its geology, chemistry and biology. Three more Pisces V dives are scheduled for February, nine in August, and five in September. There are tentative plans for planting permanent seismic arrays (transmitting data to land via fiber optic cables), and some deep drilling. Meanwhile, if you are interested in Loihi, a series of papers will be presented at a special symposium on 11 December, during the American Geophysical Union's annual meeting in San Francisco. -- Bob Cunningham bob@loihi.hig.hawaii.edu