HR: 10:20h
AN: V11G-01    [PDF]
TI: Spreading Flanks of Ocean-Island Volcanoes: Similarities and Differences at Mauna Loa and Kilauea, Hawaii
AU: * Lipman, P W
EM: plipman@usgs.gov
AF: Volcano Hazards Teadm, U.S. Geological Survey, 345 Middlefield Rd, Menlo Park, CA 94025 United States
AU: Eakins, B W
EM: beakins@usgs.gov
AF: Volcano Hazards Teadm, U.S. Geological Survey, 345 Middlefield Rd, Menlo Park, CA 94025 United States
AU: Yokose, H
EM: yokose@sci.kumamoto-u.ac.jp
AF: Dept. Earth Science, Kumamoto University, 2-39-1 Kurokami, Kumamoto, 860-8555 Japan
AB: Submarine-flank deposits of Hawaiian volcanoes are widely recognized to have formed largely by gravitationally driven volcano spreading and associated landsliding. Observations from JAMSTEC submersibles (Japan Marine Science and Technology Center) show that prominent benches at mid-depths on flanks of both Mauna Loa and Kilauea consist of volcaniclastic debris derived by landsliding from nearby shallow submarine and subaerial flanks of the same edifice. Both volcanoes have mid-slope benches that record the same general processes of slope failure on varying scales, followed by modest compression during continued volcano spreading, even though they record development during different stages of edifice growth. Massive slide breccias from the mature subaerial tholeiitic shield of Mauna Loa underlie the frontal scarp of its South Kona bench. Outboard of the South Kona bench are large slide blocks, containing mixed subaerial and submarine Mauna Loa rocks, that appear to constitute a distal facies of the same large landslide event(s). The dive results also suggest that volcaniclastic rocks at the north end of the Kona bench, interpreted by others as distal sediments from older volcanoes that were offscraped, uplifted, and accreted to the island by far-traveled thrusts, alternatively are a largely coherent stratigraphic assemblage deposited in a basin behind the South Kona bench. In contrast, the Hilina bench developed as Kilauea volcano has spread seaward, in part riding piggyback on the still active south flank of Mauna Loa. The Hilina bench is underlain by coarse volcaniclastic sediments derived largely from submarine-erupted pre-shield alkalic and transitional basalts of ancestral Kilauea. The south flank of Kilauea is thus far not associated with any massive slide deposits comparable to the distal blocks of the South Kona slide complex.
DE: 8414 Eruption mechanisms
DE: 8434 Magma migration
DE: 8499 General or miscellaneous
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting