bob@uhmanoa.UUCP (02/19/87)
Shimmering flows of magma-heated water, flakes of white bacteria swirling like snow, a new species of fish that looks like a titanic toad, and rocks that fizzle when you take them to the surface... A few of the interesting things seen in the first close-hand look at Loihi, Hawaii's active underwater volcano. Over the past week, Loihi, the lava-laced underwater Volcano some 21 miles southof the Big Island of Hawaii got its first human visitors. They roade to depths of almost a mile in the Alvin submersible (best known for its exploration of the wreck of the Titanic). In the dark depths, they found a rocky, slimy moonscape almost surprisingly devoid of life...but with extremely high concentrations of pressurized carbon dioxide. Sampled rocks, when brought to the surface, fizzled like soda cans. What they didn't find: no extremely hot water, the warmest water measurements averaged 87 degrees Fahrenheit, hot only compared to the usual temperaterature of surrounding seawater at that depth; no active chimneys of geyser-like "black smokers" (like the ones that gush up 600-degree water along the East Pacific Rise spreading center); not very many animals, only those norally associated with seamounts, the usual eel-like fishes and rattails (except for a new species of toad-like fish, two of which were captured and brought to the surface). Pending taxonomic classification (quite likely a new genus as well as a new species), the ugly fishes were given the working nickname "Nierenberg", in honor of a former director of Scripps Institute of Oceanography in California. Some small (3-foot high) chimneys were found, forming a field of relatively low-temperature vents, and the main location where they were found was christened the "field of a thousand fingers". General observations by the geologists in the expedition was that volcanism on Loihi seemed to be occuring in a spotty, sporadic manner. Most of the exploration centered on the broad central plateau topping Loihi. Further exploration over the next couple of days will home in on the two major crator features at the southern end of the summit plateau. [I describe it as a "plateau" because that's the way it appears from the submerisble, from bathymetric data, it's rather obvious that it's actually a shallow caldera---formed by a partial collapse of the top of the volcano.] One of the major objectives of the next set of dives is to collect a representative sample of basaltic rocks from different parts of the inside of those craters. Extensive chemical analysis (using mass spectrometers and other techniques) is expect to tell a lot about the nature and times of eruptive activity. Two theories have been proposed for the relative sparsity of life on Loihi. One is that the high CO2 levels (4,000 times that of the surrounding seawater) is acting as a poison to creatures which might metabolize the seamount's methane and hydrogen sulfide. Other other theory is that the surface is just too young to have established colonies of crabs, worms or other animals that can live off methane or sulfides. Some of the more poetic observations, from a biologist's notes made on while on the bottom (made during Alvin dive number 1,800): "Birth [of an island] is painful. Laboring to reach the suface, heaving under the weight of 100 atmospheres of pressure from the overlying water, streams of hot water gently [are] pouring out like the volcano is purring---perhaps building up for the next good blow, when pillows [pillow lava=typical underwater formation] will pile into massive rock mounds, fracture and collapse into undersea avalanches, rumbling down slope. -- Bob Cunningham bob@hig.hawaii.edu