V53E-01:
When Do Complex Eruption Dynamics Matter? The Roles of Column Instability and Magma-water Interaction on Dispersal of Volcanic Ash
Friday, 19 December 2014: 1:40 PM
Alexa R Van Eaton, Arizona State University, School of Earth and Space Exploration, Tempe, AZ, United States; USGS Cascades Volcano Observatory, Vancouver, WA, United States, Michael Herzog, University of Cambridge, Cambridge, United Kingdom, Amanda B Clarke, Arizona State University, Tempe, AZ, United States and Richard J Brown, University of Durham, Department of Earth Sciences, Durham, United Kingdom
Abstract:
Many eruptive sequences are associated with some amount of column instability (leading to production of ground-hugging flows) and interaction with surface water. These factors can fundamentally alter the vertical distribution of mass in the volcanic plume, and the rates and styles of particle aggregation. However, it is not clear when near-source complexities factor significantly into the long-distance dispersal of volcanic ash. In studies of the regional to global-scale impacts of explosive volcanism, when are these processes crucial, and when can they simply be ignored? Here, we use field observations of particle aggregation with coupled 3D numerical modeling of near-source and distal ash cloud evolution (using ATHAM and Ash3d, respectively) to examine a range of recent and prehistoric eruptions. In particular, the eruptions of Redoubt Volcano, Alaska (2009), Mount St. Helens, USA (1980), Oruanui, New Zealand (25.4 ka), and Ilopango, El Salvador (~536 AD) will provide field constraints to test the sensitivity of distal dispersal to proximal column dynamics.
