Abstract
Flow direction patterns have been determined by imbrication measurements of pumice and lithic fragments of the Handa pyroclastic flow deposit, in order to estimate the source vent location and to analyze the flow behavior. The pyroclastic flow deposit studied is dacitic in composition, 2 km2 in volume, and >32,300 Y.B.P. in age. Flow directions from 52 outcrops indicate a source vent located within the area of recent lava domes of Kuju Volcano. The distribution of the pyroclastic flow deposit and the flow direction patterns determined by imbrication suggest that the pyroclastic flow accurately followed the topographic relief at the time of eruption. The presence of imbrication indicates the change of flow-regime from turbulent condition to laminar condition according to the distance from the source vent. Imbrication is visible within the lower-half reaches of the pyroclastic flow distribution, where the pyroclastic flow had developed the laminar flow characteristics of a dense gravity current.
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Kamata, H., Mimura, K. Flow directions inferred from imbrication in the Handa pyroclastic flow deposit in Japan. Bull Volcanol 46, 277–282 (1983). https://doi.org/10.1007/BF02597562
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DOI: https://doi.org/10.1007/BF02597562