HR: 0800h
AN: V51D-0776    [Abstracts]
TI: Laboratory Studies of High Temperature Deformation and Fracture of Lava Domes
AU: * Smith, R
EM: rosanna.smith@ucl.ac.uk
AF: Mineral Ice and Rock Physics Laboratory, Department of Earth Sciences, UCL, Gower Street, London, WC1E 6BT,
AU: Sammonds, P
EM: p.sammonds@ucl.ac.uk
AF: Mineral Ice and Rock Physics Laboratory, Department of Earth Sciences, UCL, Gower Street, London, WC1E 6BT,
AU: Tuffen, H
EM: h.tuffen@lancaster.ac.uk
AF: Department of Environmental Science, Lancaster University, Lancaster, LA1 4YQ,
AU: Meredith, P
EM: p.meredith@ucl.ac.uk
AF: Mineral Ice and Rock Physics Laboratory, Department of Earth Sciences, UCL, Gower Street, London, WC1E 6BT,
AB: The high temperature fracture mechanics of magma at high temperatures exerts a fundamental control on the stability of lava domes and the timing and style of eruptions at andesitic to dacitic volcanoes. This is evidenced in the pervasive fracturing seen in both ancient and active magma conduits and lava domes; in addition to the volcanic earthquakes that occur before and during episodes of dome growth and dome collapse. Uniaxial and triaxial deformation experiments have been performed on crystal rich and crystal free magmas (andesite from Ancestral Mount Shasta, California, USA and a rhyolitic obsidian from Krafla, Iceland) at a range of temperatures (up to 900°C), confining pressures (up to 50 MPa) and strain rates (10^-5s^-1) to 10^-3s^-1) whilst recording acoustic emissions (AE). Results from these experiments provide useful inputs into models of lava dome stability, extrusion mechanisms, and source mechanisms for volcanic earthquakes. However, the large sample sizes used to ensure valid results (25mm diameter and 75mm length) made it difficult to maintain stable high temperatures under confined conditions. Also, only rudimentary AE data could be obtained, due to the distance of the transducers from the samples to keep them away from the high temperatures. Here, we present modifications to this apparatus, which include a new furnace, improved loading system, additional pore pressure and permeability measurement capability, and vastly improved acoustic monitoring. This allows (1)stable higher temperatures (up to 1000°C) to be achieved under confined conditions, (2) high temperature and moderate pressure (up to 70 MPa) hydrostatic measurements of permeability and acoustic velocities, (3) high temperature triaxial deformation under different pore fluid and pressure conditions, and (4) full waveform AE monitoring for all deformation experiments. This system can thus be used to measure the physical properties and strength of rocks under volcanic conditions and to simulate volcanic earthquakes.
DE: 5102 Acoustic properties
DE: 5104 Fracture and flow
DE: 8414 Eruption mechanisms and flow emplacement
DE: 8419 Volcano monitoring (7280)
DE: 8429 Lava rheology and morphology
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting