HR: 1330h
AN: V22A-0568    [PDF]
TI: Numerous Submarine Radial Vents Revealed on Mauna Loa Volcano
AU: * Wanless, D
EM: dwanless@soest.hawaii.edu
AF: Dept. of Geology and Geophysics, University of Hawaii, Honolulu, HI 96822 United States
AU: Garcia, M O
EM: garcia@soest.hawaii.edu
AF: Dept. of Geology and Geophysics, University of Hawaii, Honolulu, HI 96822 United States
AU: Rhodes, J M
EM: jmrhodes@eclogite.geo.umass.edu
AF: Dept. of Geosciences, University of Massachusetts, Amherst, MA 01003 United States
AU: Trusdell, F A
EM: trusdell@usgs.gov
AF: U.S. Geological Survey, Hawaii Volcano Observatory, HVNP, HI 96718 United States
AU: Schilling, S
EM: sschilli@usgs.gov
AF: U.S. Geological Survey, Hawaii Volcano Observatory, HVNP, HI 96718 United States
AU: Weis, D
EM: dweis@eos.ubc.ca
AF: Dept. of Earth and Ocean Sciences, University of British Columbia, Vancouver, BC V6T_1Z4 Canada
AU: Fornari, D
EM: dfornari@whoi.edu
AF: Whoi, Woods Hole, Woods Hole, MA 02543 United States
AU: Vollinger, M
EM: mikev@geo.umass.edu
AF: Dept. of Geosciences, University of Massachusetts, Amherst, MA 01003 United States
AB: Among Hawaiian shield volcanoes, Mauna Loa is distinct in having vents outside of its summit and rift zones. These radial vents are located on its northern and western flanks and account for approximately 10% of historic eruptions outside the summit region. Thirty-three subaerial and one submarine vent (active in 1877) were known prior to our work. During a recent Jason2 expedition to the volcano's western flank, nine new submarine radial vents were discovered. Eighty-five samples were collected from these and the 1877 radial vent. Bathymetry and side-scan imagery were acquired using an EM300 multibeam echo sounder. The high resolution data (vertical resolution of approximately 4 m and horizontal resolution of 25 m) allowed us to create the first detailed geologic map of Mauna Loa's western submarine flank. The map was compiled using video and still photography from the Jason2 ROV and geochemical analysis of the samples. The geochemistry includes microprobe glass and XRF whole rock major and trace element data. Eight of the submarine radial vents sampled erupted tholeiitic lavas that are geochemically similar to historical subaerial eruptions on Mauna Loa. However, in contrast to all previously collected Mauna Loa lavas, two of the young vents erupted alkalic basalts. These lavas may have been derived from Mauna Loa, as they have somewhat higher FeO and TiO2 values at a given MgO content than alkalic lavas from neighboring Hualalai volcano, whose vents are located only on rifts 16 km away. Alkalic lavas are indicative of the postshield stage of volcanism and may signal the impending demise of Mauna Loa volcano.
DE: 1000 GEOCHEMISTRY (New field, replaces Rock Chemistry)
DE: 8400 VOLCANOLOGY
DE: 9355 Pacific Ocean
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting