Lava-Dam Outburst Floods and Related Volcanic Features in Western Grand Canyon

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Lava-Dam Outburst Floods and Related Volcanic Features in Western Grand CanyonPIs propose to use cosmogenic 3He dating combined with hydrologic, petrographic, and geochemical techniques to resolve the history of Quaternary outburst floods in the Colorado River. This work will be supplemented by 40Ar/39Ar work on some lava flows, and by geochemical characterization of lavas. Preliminary 3He dating provides evidence for lava flows and outburst floods much younger than have been previously dated by K/Ar, significantly changing interpretations of the geomorphic evolution of western Grand Canyon. They will date basalt surfaces scoured by major flood events, outburst flood deposits, lava flows, abandoned scour channels, and perched boulder bars to constrain late Quaternary events in the western Grand Canyon. This work will allow them to correlate lava flows with lava dams and outburst flood deposits and to estimate flood magnitudes based on paleoflood evidence. This work will significantly change interpretations of the geomorphic evolution of western Grand Canyon because of the ability to accurately date events of the last 0.5 million years.