HR: 08:15h
AN: V41I-02    [Abstracts]
TI: Fracturing as a Quantitative Indicator of Lava Flow Dynamics
AU: * Kilburn, C R
EM: c.kilburn@ucl.ac.uk
AF: University College London, UCL Benfield Hazard Research Centre, Department of Earth Sciences, Gower St, London, WC1E 6BT United Kingdom
AU: Solana, C
EM: Carmen.Solana@port.ac.uk
AF: University of Portsmouth, School of Earth and Environmental Sciences, Burnaby Road, Portsmouth, PO1 3QL United Kingdom
AB: The traditional classification of lava flows into pahoehoe and aa varieties reflects differences in how a flow can fracture its surface during advance. Both types of lava have a low strength upon eruption and require surface cooling to produce a crust that can fracture. Among pahoehoe lavas, applied stresses are small enough to allow the growth of a continuous crust, which is broken intermittently as the flow advances by propagating a collection of lava tongues. Among aa lavas, in contrast, applied stresses are large enough to maintain persistent crustal failure. The differences in fracturing characteristics has been used to quantify the transition between flow regimes and suggests that shear fracture may dominate tensile failure. Applied to Lanzarote, the model confirms the inference from incomplete eye-witness accounts of the 1730-36 Timanfaya eruption that pahoehoe flows were able to advance about an order of magnitude more quickly than would have been expected by analogy with Hawaiian pahoehoe flow-fields of similar dimensions. Surface texture and morphology, therefore, are insufficient guides for constraining the rate and style of pahoehoe emplacement. Applications include improved hazard assessments during effusive eruptions and new evaluations of the emplacement conditions for very large-volume pahoehoe lava flows.
DE: 8414 Eruption mechanisms and flow emplacement
DE: 8425 Effusive volcanism
DE: 8429 Lava rheology and morphology
DE: 8488 Volcanic hazards and risks
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005