Topographic Controls on the Generation of Elutriated Ash Clouds: II. Nature and Dynamics of Pyroclastic Density Currents

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9725361 Bursik Pyroclastic flows or nuees ardentes are perhaps the most destructive, yet most poorly understood of volcanic phenomena. Because of their destructiveness, they are virtually impossible to observe directly; yet they leave deposits that have proven extremely difficult to interpret. The primary objective of the proposed research is to determine in specific, well-constrained situations the link between active flow conditions in pyroclastic flows and the resulting deposits. Because we may be able to determine what is happening within the flows, the results could have important ramifications for the simulation of flows in hazards analysis, and for volcanic hazards assessment. The proposed work will procede with experimental, theoretical and fieldwork phases. The work will begin by carefully making deposits in the laboratory under well-constrained flow conditions, using special facilities designed only for the purpose of these studies. Theoretical modeling will extend the range of applicability of the experiments by generalizing the observed flow mechanics. Laboratory and theoretical results will be tested by careful sedimentological analysis of certain diagnostic portions of pyroclastic flow deposits, especially modern deposits for which there is some information on active flow conditions.