HR: 1340h
AN: V33D-1485    [Abstracts]
TI: Experimental Insights into the role of Dynamic Gas-slug Expansion on the Nature of Strombolian Eruptive Activity
AU: * Lane, S J
EM: s.lane@lancaster.ac.uk
AF: Lancaster University, Department of Environmental Science, Lancaster, LA1 4YQ United Kingdom
AU: Corder, S
EM: s.corder@lancaster.ac.uk
AF: Lancaster University, Department of Environmental Science, Lancaster, LA1 4YQ United Kingdom
AU: James, M R
EM: m.james@lancaster.ac.uk
AF: Lancaster University, Department of Environmental Science, Lancaster, LA1 4YQ United Kingdom
AB: The exsolution of gaseous species to form bubbles is common as magma approaches the Earth's surface. Under certain conditions of time-scale and magma viscosity, bubbles can move relative to their host liquid and undergo collision and coalescence processes. These processes are enhanced by conduit inclination, significant wall roughness and major conduit discontinuities. The result is the generation of large gas slugs which form the basis of Strombolian eruptive activity. The behaviour of gas slugs in tubes has been the subject of extensive research, because it is critical to many chemical industries. For insight into volcanological processes, physically small laboratory experiments are scaled by exploring the range of viscous, inertial and surface-tension controlled events. However, these experiments remain unscaled in terms of expansion ratio, (P*), defined here as the ratio of the pressure at which the gas slug was created, (Ps), to the ambient pressure at the top of the magma column, (Pv), i.e., P*=Ps/Pv. In the laboratory case P* is rarely greater than 1.5, some 1 to 3 orders of magnitude less than the value pertinent to volcanic conduits. The consequence of this is that experimental gas slugs will not be subject to the same degree of dynamic super-static pressurization generated by accelerating the magma overburden as the gas slugs giving rise to Strombolian eruptions. In order to increase P* within the laboratory, a denser liquid phase, longer (higher) conduit or reduced 'ambient' pressure (Pv) can be used. We utilise the latter technique, connecting the upper end of the experimental flow tube to a vacuum system. By varying Pv, experiments covering a range of P* values scaled to conduit processes can be carried out. We explore the behaviour of expanding gas slugs, and the pressures and forces generated during rise and bursting. The volcanological implications for eruptive style and volcano-seismic interpretation are discussed.
DE: 8414 Eruption mechanisms
DE: 8419 Eruption monitoring (7280)
DE: 7280 Volcano seismology (8419)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting