HR: 1340h
AN: V23A-0617    [Abstracts]
TI: Tephras and the History of Volcanism, Recent Tectonism, and Tsunamis in Lower Cook Inlet, Alaska
AU: * Davis, K M
EM: ftkmd@uaf.edu
AF: University of Alaska Fairbanks, Department of Geology and Geophysics P.O. Box 755780, Fairbanks, AK 99775
AU: Beget, D
EM: ffjeb1@uaf.edu
AF: University of Alaska Fairbanks, Department of Geology and Geophysics P.O. Box 755780, Fairbanks, AK 99775
AB: Cook Inlet is located on the western side of the Kenai Peninsula in south-central Alaska. Past eruptions from Augustine volcano and other volcanoes have had significant impacts on the lower Cook Inlet communities. Tephra layers from prehistoric and historic eruptions are preserved within peat sequences along Kachemak Bay, near Homer, Alaska. Evidence of active tectonism is found where thick marine muds overlie peat deposits along Kachemak Bay. The marine mud deposits record co-seismic subsidence that occurred during a prehistoric great earthquake on the northern pacific subduction zone. Two layers of sand and beach gravel also occur within the peat deposits. The sedimentology is identical to classic tsunami deposits identified in other tectonically active areas, and we interpret these deposits as evidence of prehistoric tsunamis. The upper sand is directly overlain by a 1.2 cm thick grayish white tephra. The sand and beach gravel associated with the tephra most likely records a tsunami triggered at the nearby Augustine volcano, while the other sand deposit may be evidence of a tectonically triggered tsunami. The recognition of tephras, tsunami deposits, and evidence of prehistoric co-seismic subsidence has significant implications for geohazards in the lower Cook Inlet area.
DE: 8400 VOLCANOLOGY
DE: 8404 Ash deposits
DE: 4564 Tsunamis and storm surges
DE: 0370 Volcanic effects (8409)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting