March 13, 2001 to June 2, 2001
Monterey to Hawaii and back
Juli Wagner writes: Several highly successful dives on the submerged reefs on Mahukona Volcano in the past several days opened up the opportunity to revisit our second refuge from the vigorous trade winds, the South Kona area. We steamed southward overnight to carry out the longest dive (15 hrs) with the highest climb (1250 meters) of the leg. We also collected the heaviest, and the most rocks, a total of 35 samples; problem is, now we have to describe them! Starting at 3250-meter water depth, we traversed a series of slump blocks along the northern seaward edge of the South Kona Landslide, just south of the margin of the Alika debris slide that we explored previously. Not surprisingly, we found massive cliffs of broken, volcaniclastic sandstones and breccias. To our surprise, many of the sediments were very fine-grained, unlike fragmental basalts one usually sees in volcanic settings. We now have to explain why. Much of the outcrop was highly sheared and fractured. We now think we can pick several major fault zones, formed when the blocks tore loose during catastrophic collapse of the southeastern flank of Mauna Loa. Fractures on the broken rock surfaces sometimes defined a "jig-saw puzzle" texture. Elsewhere, submarine erosion left dramatically sculpted chutes and gullies.
A "family" of tripod fish provided us with relief from the massive cliffs of broken rock that made up much of this dive. They stand out, because they prop themselves up on 3 long fins, standing nearly a meter high. We ran into these unusual fish at least 4 times during the dive!! Sometimes they were found in pairs, other times towering above their close relative, the spiderfish, perched on slightly shorter fins. A colorful sea urchin proved to be the owner of a furrowed terrace we crossed along the way. We also encountered several sea cucumbers, and a bizarre, unidentified animal with a big "tongue" and long "mustache".