HR: 15:10h
AN: V13E-07    [Abstracts]
TI: The Influence of Crustal Thickness and Slope on the Surface Morphology of Active Lava Flows: an Experimental Approach
AU: * Applegarth, L J
EM: jane.applegarth@univ.oxon.net
AF: Department of Environmental Sciences, Lancaster University, Lancaster, LA1 4YQ, United Kingdom
AU: James, M R
EM: m.james@lancaster.ac.uk
AF: Department of Environmental Sciences, Lancaster University, Lancaster, LA1 4YQ, United Kingdom
AU: van Wyk de Vries, B
EM: B.vanwyk@opgc.univ-bpclermont.fr
AF: Laboratoire Magmas et Volcans, 5 rue Kessler, Clermont Ferrand, 63038, France
AU: Pinkerton, H
EM: h.pinkerton@lancaster.ac.uk
AF: Department of Environmental Sciences, Lancaster University, Lancaster, LA1 4YQ, United Kingdom
AB: Many of the surface features that develop on `a`a and blocky lava flows relate to internal dynamics during flow emplacement, but it can be difficult to infer the precise relationships between morphology and dynamics from observations of flows either during or after their emplacement. Experiments using PEG have greatly improved our understanding of the behaviour of lavas with relatively thin crusts. Here we describe an alternative approach (similar to that of Lescinsky and Merle (2005), GSA Special Paper 396, p.136) in which the crust plays a significant role in flow development. Our experiments investigated the effect of crustal thickness and slope on the morphological development of channelised distal flows. The materials used were high viscosity (10⁴ Pa s) silicone gel to simulate the still-fluid lava, and a mix of sand and plaster to represent the cohesive brittle crust and the confining levees. Experiments were conducted on an inclined board with a reservoir constructed at one end. Silicone was released from the reservoir through a sliding gate, where it encountered a seed flow consisting of a silicone sheet topped with a crust of known depth and constrained by levees. The models therefore represented the influx of fresh lava into a channel. Sequential digital images taken over the course of each experiment allowed marker points on the flow surface to be tracked, and these data were used to construct surface velocity maps. Several experiments were recorded using stereo imagery, allowing changes in the surface relief to be monitored. The insights from these quantitative techniques, combined with morphological observations, are used to illustrate the effect of the crust on the flow dynamics, and to show the response of the brittle crust to the movement of the viscous flow interior. An overview of the experimental techniques and results will be presented, together with an assessment of how the observed model morphologies can be related to features observed in the field.
DE: 8414 Eruption mechanisms and flow emplacement
DE: 8429 Lava rheology and morphology
DE: 8445 Experimental volcanism
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting