Paper No. 145-12
Presentation Time: 10:50 AM
THE MANY LIVES OF LAWETLAT'LA: THE PAST, PRESENT, AND FUTURE OF TEPHRA RESEARCH AT MOUNT ST. HELENS (Invited Presentation)
Mount St. Helens is the most active volcano in the Cascades and one of the most studied. The extent of its past activity was unclear until mapping by Donal Mullineaux and Dwight Crandell revealed major active episodes interspersed with variable periods of quiescence. In 1975 they predicted it would erupt again, mostly likely in the next century, and on May 18th 1980 Mount St. Helens proved them dramatically correct. Throughout its mapped history, eruptions from this volcano have regularly dispersed ash across large swaths of the western USA and Canada. However, despite the common presence of Mount St. Helens ash at stratigraphic and archaeological sites, the identification and correlation of these distal ashes to the proximal stratigraphy at Mount St. Helens has been challenging due to limited availability of glass geochemical data as well as some uncertainty in the ages of eruptions. For this talk I will discuss the history of tephra research at Mount St. Helens, the development of the proximal stratigraphy, and why we are revisiting this original work to help us understand the distal tephra record from this volcano. I will provide an overview of what we have discovered so far, including the common presence of Mount St. Helens ash in peat cores from northeastern North America, and discuss future research directions. This volcano sits at the intersection of classic tephrochronology and volcanological research – a natural laboratory that allows us to explore questions around ash dispersion, volume, preservation, and prediction.