Morphology, Volcanism, and Mass Wasting in Crater Lake, Oregon
Morphology, volcanism, and mass wasting in Crater Lake, Oregon Charles R. Bacon* Volcano Hazards, U.S. Geological Survey, 345 Middle®eld Road, MS 910, Menlo Park, California 94025-3591, USA James V. Gardner Western Coastal and Marine Geology, U.S. Geological Survey, 345 Middle®eld Road, M.S. 999, Menlo Park, California 94025- 3591, USA Larry A. Mayer Center for Coastal and Ocean Mapping, University of New Hampshire, 24 Colovos Road, Durham, New Hampshire 03824, USA Mark W. Buktenica National Park Service, Crater Lake National Park, P.O. Box 7, Crater Lake, Oregon 97604, USA Peter Dartnell Western Coastal and Marine Geology, U.S. Geological Survey, 345 Middle®eld Road, M.S. 999, Menlo Park, California 94025- 3591, USA David W. Ramsey Joel E. Robinson Volcano Hazards, U.S. Geological Survey, 345 Middle®eld Road, M.S. 910, Menlo Park, California 94025-3591, USA ABSTRACT The ¯at-¯oored, deep basins contain relatively ®ne-grained sedi- ment transported from the debris aprons by sheet-¯ow turbidity Crater Lake was surveyed nearly to its shoreline by high-reso- currents. Crater Lake apparently ®lled rapidly (ca. 400±750 yr) lution multibeam echo sounding in order to de®ne its geologic his- until reaching a permeable layer above glaciated lava identi®ed by tory and provide an accurate base map for research and monitor- the new survey in the northeast caldera wall at ;1845 m elevation. ing surveys. The bathymetry and acoustic backscatter reveal the Thereafter, a gradual, climatically modulated rise in lake level to character of landforms and lead to a chronology for the concurrent the present 1883 m produced a series of beaches culminating in a ®lling of the lake and volcanism within the ca.
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