HR: 0800h
AN: V21B-0600    [Abstracts]
TI: Tsunami Deposits Related to Volcanic Island Collapses in the Southern Bismarck Sea
AU: * Morgan, E
EM: emotown@hotmail.com
AF: University of California, Earth Sciences Dept. 1156 High Street, Santa Cruz, CA 95064 United States
AU: Day, S
EM: sday@pmc.ucsc.edu
AF: University of California, Earth Sciences Dept. 1156 High Street, Santa Cruz, CA 95064 United States
AU: Elemunop, J
EM: jason_elemunop@mineral.gov.pg
AF: Geological Survey of Papua New Guinea, Private Mail Bag, Port Moresby, 12345 Papua New Guinea
AU: Silver, E
EM: esilver@pmc.ucsc.edu
AF: University of California, Earth Sciences Dept. 1156 High Street, Santa Cruz, CA 95064 United States
AU: Ward, S
EM: sward@pmc.ucsc.edu
AF: University of California, Earth Sciences Dept. 1156 High Street, Santa Cruz, CA 95064 United States
AU: Hoffmann, G
EM: garyh@pmc.ucsc.edu
AF: University of California, Earth Sciences Dept. 1156 High Street, Santa Cruz, CA 95064 United States
AB: The timing and magnitude of tsunami resulting from volcanic island collapses can be constrained by the deposits they leave on proximal coastline. We examined tsunami deposits on the southern portion of the Bismarck Sea, where volcanic island collapse has occurred, including Ritter Island in 1888. We also discovered at least a dozen additional collapse events as a result of geophysical studies of the Bismarck volcanic chain. Carbon dating of a few stratigraphically successive, coralline deposits in Madang Lagoon documents tsunami events at 550, 2600, and 3200 years before present, eliminating the recent Ritter collapse as a source. Other possibilities include collapses observed from Karkar, Crown, or Long Islands, or more local sources from islands in the lagoon. The tsunami deposits in this study show less sorting and a greater distribution from shore than storm deposits observed at the same locations. Furthermore, a landward fining of clasts characterizes tsunami deposits, compared with seaward fining of storm deposits. Using hydrodynamic transport equations coupled with clast size and distance from shore, we infer the rate at which the tsunami of 550 years ago lost height and velocity with distance inland.
DE: 8404 Volcanoclastic deposits
DE: 8455 Tephrochronology (1145)
DE: 8488 Volcanic hazards and risks
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005