HR: 13:40h
AN: V23E-01 INVITED    [Abstracts]
TI: Insights Into Subaqueous Explosive Eruptions From the Dynamics of Underwater Explosions
AU: * Walder, J S
EM: jswalder@usgs.gov
AF: US Geological Survey Cascades Volcano Observatory, 1300 SE Cardinal Ct., Bl. 10, Suite 100, Vancouver, WA 98683, United States
AB: During an underwater chemical explosion, the explosive is transformed into a high-pressure mixture of gases and particulate debris that expands and displaces the surroundings. This expanding mixture forms a bubble, albeit one a great deal larger than the bubbles of everyday experience. Interaction of the explosion bubble with the water surface may send water and particulate debris to great height and in various directions. Assuming that an explosion bubble is generated during a subaqueous eruption and that the bubble behaves in the same way as one generated by a high explosive, characteristics of the subaerial "splash" may be used to make quantitative inferences about the energetics of explosive subaqueous eruptions . The comparison relies on empirical relationships between two characteristics of the splash (maximum height and initial speed) and explosion depth, all cast in a suitable nondimensional form derived from the theory of underwater explosion bubbles. Available data for subaqueous basaltic eruptions can be brought into agreement with the experimental relationship for underwater chemical explosions only if the enthalpy release during the volcanic explosions is at most a few percent of the enthalpy (relative to the boiling point of water) of the erupted mass of magma. Comparable "inefficiency" has been found in a range of experiments on molten fuel/coolant interactions, which are commonly thought to be the fundamental driving mechanism of phreatomagmatic explosions. Experimental studies of underwater chemical explosions also provide a framework for understanding some sedimentological aspects of explosive subaqueous eruptions, such as the way that basaltic pyroclasts interact with liquid water after magma fragmentation and the presence of clasts that seem to have been deposited subaqueously in a dry state.
DE: 8404 Volcanoclastic deposits
DE: 8427 Subaqueous volcanism
DE: 8428 Explosive volcanism
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting