| Francisco Chavez's chlorophyll filtration manifold and fluorometer, 40lbsаPlanned Track Description:Planned Track Description:The summit of Loihi Seamount is partly covered by volcaniclastic sedimentary deposits that were discovered and sampled during a series of submersible dives with the Pisces V in 1996, 1997, and 1998 (done by invitation from Frank Sansone and Geoff Wheat in 1996 and 1997 and as a HURL-funded 3-dive program with Rodey Batiza and Jim Head in 1998). The deposits found in the first two years consisted of thin sand units with ripple marks that included bubble-wall fragments indicating that mild explosive activity had occurred on the summit of Loihi (Clague et al., 2000). This discovery led us to explore more specifically for thicker explosive deposits on the summit, which were then found in 1998. The deposits discovered in 1998 include an 11-m section of ash exposed along an inward-facing normal fault, identified in the MBARI Simrad bathymetric data collected in 1998, that defines a caldera complex on the flat summit region of the volcano. Some samples were collected, mainly using sediment scoops that mixed the materials from different layers. Other dives in the summit region suggest that these deposits cover much of the summit platform, particularly on its eastern side. The ash sequence consists of bedded deposits of alternating fine and coarse ash to gravel that were deposited during a variety of submarine explosive eruptions. The eruptions include Strombolian-style that produced scoria and built cinder cones, Hawaiian-style fire fountains that produced widespread deposits of lava bubble-wall fragments in silt- to clay-sized glass matrix, and phreatic explosive-style eruptions that excavated hydrothermally altered lavas and hydrothermal sulfides and sulfate deposits from the subsurface and scattered fragments of them across the summit region of Loihi. Such rapidly quenched glasses are ideal for volatile exsolution studies and we are currently analyzing some of the 1998 samples to estimate their pre=eruptive volatile contents.The scoop samples contain rare foraminifers that may occur in specific layers formed during hiatuses in eruptive activity and rare ash fragments from explosive eruptions on Kilauea Volcano. Both the foraminifers and Kilauea ashes may serve to provide age control on the ash sequence. We (Davis and Clague, 1998) have speculated that such explosive eruptions may be related to collapse events such as that in 1996 that formed a new pit crater 300 m deep and about 1-km in diameter (The Loihi Science Team, 1997).67-85 35.6200 124.5500 2 CTD, nets D3, Free Gay Incest Sex Stories BOG: Francisco Chavez, Tim Pennington, Paul Chua, and 1 un-identified female.Scheduled End Dateа: 22001-05-18 TBD Local Moss Landing timeBenthic sled with manipulator
D4 33.1300 130.59 9 DIVE, nets, CTDD6 28.8200 141.6200 9 DIVE, nets, CTDScheduled Start Date: 2001-04-21 0800 Local Moss Landing timetop of pageCT-probe (new)а Gay Prison Sex Stories top of pageThe northeast flank of Oahu shares many characteristics with the north slope of Molokai. The outer part of an terrace is punctuated by a large volcanic cone, most probably related to the rejuvenated stage Honolulu Volcanics on Oahu (Clague and Frey, 1982). This area was mapped with the Simrad EM300 system by the U.S. Geological Survey in 1998, just before the MBARI surveys were collected. The objectives in sampling this cone are similar to those outlined in the section on "Submarine cones and flows" and it is singled out here simply because it is located in a different region.Hilo Ridge was long thought to be the submarine rift zone of Mauna Kea Volcano (e.g., Yang et al., 1994, 1998), but is now proposed to be the submarine southeast rift zone of Kohala Volcano (Holcomb et al., 2000). Samples collected from the rift zone have variable chemisty-some of the dredged samples are geochemically similar to lavas from Kohala, Mauna Kea, and even Kilauea, but none are geochemically similar to the Mauna Kea lavas from near the bottom of the 1.1-km Hawaii Scientific Drilling Project pilot hole drilled near Hilo (Stolper et al., 1996).Younger flank eruptions from Mauna Kea Volcano almost certainly occur in the area, as vents from Mauna Kea are scattered over a large region on land. However, the rift zone is characterized by numerous flat-topped low-aspect ratio cones (Clague et al., 2000) and two submarine (lacking summit craters) steep-sided cones that are probably constructed of alkalic basalt after the tholeiitic shield volcano had been constructed. We want to sample and date (using Ar-Ar techniques) several of the flat-topped cones along the rift to determine if they are similar in age and chemically similar to shield lavas from Kohala or Mauna Kea volcanoes. In addition, we want to confirm that the steep cones are composed of alkalic basalts, determine their eruptive style and depth, and determine when they erupted, providing a maximum age for th ... |
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