bob@uhmanoa.UUCP (Bob Cunningham) (10/19/87)
[My monthly or so informal report on Kilauea Volcano...this month including mention of interesting developments at the MacDonald and Loihi Seamounts as well.] One of the best public shows in 13 years (the last time it was easy to view Kilauea's lava flowing into the sea) is now underway as lava pours across the extreme southeast corner of the Hawaii Volcanoes National Park and into the Pacific Ocean. Lava which last week cut through a corner of the Royal Gardens subdivision (destroying several more houses) and across the Chain of Craters Road is continuing into the ocean at a point about 3/4 of a mile from the Park's Wahaula Visitor Center. All previous recent flows met the ocean after crossing private land just outside the Park's boundaries, and County authorities prevented people from crossing the private land; the closest visitors could get was Kupapau point and watch the flows across the small bay. Authorities are currently trying to keep people---except the few residents left---out of the Royal Gardens subdivision itselfin part because of the danger from exploding trees, and in part because the remaining residents feel a bit hasseled by all the tourists as well as the lava. Now, it's possible to walk to within about 100 feet of the flow where it's going into the ocean, being held back only by the clouds of steam and sulfurous fumes (the walk is definitely not recommended for anyone with respiratory problems). The flow into the ocean seems to be relatively quiet, not producing any of the somewhat dangerous steam-powered explosions that often occur when lava flows into the ocean. Meanwhile, up at the rift zone vent where all this lava is coming from, Kilauea continues to produce the steady 4.9 cubic meters per second worth of lava that it has been producing over the last 3 years or so. The "lava lake" remains about the same size & shape it has been for the last several months, with its overflow feeding the stream of lava to the ocean. Mauna Loa is not in eruption, and there are no indications of an eruption from it soon. MacDonald Seamount... Last Monday (13 Oct), the Scripps ship R/V Melville serendiptiously found itself over the MacDonald Seamount as it erupted. According to Harmon Craig, chief scientist on board, the experience was spectacular. There was a fearful clamor as large bubbles of steam and volcanic gas shook the ship, bursting under her hull and in the surrounding water. It seems that the sporadic eruptions of the MacDonald Seamount are the source of previously-mysterious seismic signals that French seismologists in Tahiti have been recording for years. Subsequent bottom samplings by the Melville brought up fresh volcanic glass from the seamount. If Craig and the Melville had their cameras going, you might just see this on some upcoming PBS show in a few months. Sounds like it's worth seeing. Macdonald Seamount, which rises to within 130 feet of the surface of the South Pacific some 750 miles southeast of Tahiti, is probably the current site of the hotspot that created the Austral (aka Tubuai) islands of French Polynesia...just as the hotspot under Loihi and Kilauea created the Hawaiian chain of islands. Loihi Seamount... Meanwhile, scientists continue to work up data from the recent August-September exploration of Loihi Seamount using the Pisces V submsersible. This was the 2nd Loihi expedition this year; the first was in Febuary using the Alvin from Woods Hole. One of the objectives was to find locations for seismic instrumentation for a planned fiber optic-linked network of instrumentation on Loihi itself. The Big Island of Hawaii, some 28 miles north, is extensively instrumented---but that gear is set up very specifically to watch Kilauea and Mauna Loa. From those instruments, it is not even obvious when Loihi is actually erupting. A considerable number of geologists want to monitor this next-Hawaiian-Island-to-be on a regular basis in detail on a regular basis without having to mount a major expedition and tying up one of the few U.S. deep-diving research submersibles. Besides the bathymetry and bottom survey data, the geochemistry data is being closely studied. Harmon Craig et al, already believes helium isotope tracers show that Loihi taps material from the earth's lower mantle (400 to 1,800 miles deep). Other isotopes should verify this. Most of the world's volcanoes sprout from much shallower sources of magma; it is likely only the "hot spots" like Loihi & MacDonald Seamounts have really deep magmatic roots. Besides differing isotopic abundances, other geochemical differences between Loihi and non-hotspot volcanoes are obvious. For example, it emits considerably more methane. Why is that interesting? Well... because Loihi draws material from the lower mantle instead of recycled crustal material as most volcanoes do, the chemical composition of its output is probably much more like that of primordial volcanoes early on in Earth's history. If Loihi's methane production is any indication, the Earth's prebiotic atmosphere may have had a much larger methane input than previously estimated, making it easier than previously estimated to produce amino acids and nucleotides prebiotically. -- Bob Cunningham bob@hig.hawaii.edu