HR: 08:48h
AN: V31D-05    [Abstracts]
TI: An analysis of the development of surface textures and flow morphology on small lava flows on Kilauea using high frame rate (30 Hz) digital thermal imagery.
AU: * Pinkerton, H
EM: h.pinkerton@lancaster.ac.uk
AF: Department of Environmental Science, Lancaster University, Lancaster, LA1 4YQ United Kingdom
AU: Harris, A
EM: harris@higp.hawaii.edu
AF: Hawai`i Institute of Geophysics and Planetology, University of Hawaii, Honolulu, HI 96822 United States
AU: Ball, M
EM: m.ball@lancaster.ac.uk
AF: Department of Environmental Science, Lancaster University, Lancaster, LA1 4YQ United Kingdom
AU: James, M
EM: m.james@lancaster.ac.uk
AF: Department of Environmental Science, Lancaster University, Lancaster, LA1 4YQ United Kingdom
AB: Understanding the way that lavas cool is an important step in the development and validation of models of lava flows, and thermal imaging cameras are playing an important role in this investigation. Recent technological advances have led to the development of uncooled thermal imaging cameras, increases in data-acquisition rates and a new generation of high frame rate cameras. During August 2004, a hand-held FLIR ThermaCAM S40 was used to collect several thousand 30 Hz thermal images from 4 active lava flows on the Pulama pali fault scarp, Kilauea volcano, Hawaii. Short observation distances (3 to 10 m) resulted in the collection of high spatial (4-13 mm) resolution thermal data. The images acquired cover the formation, cooling, inflation and budding of new pahoehoe lobes and the formation of a range of surface textures on a small (35 m long) open channel flow. The images reveal the temperatures at which these flows developed surface textures such as a ductile crust and ropes, together with the transitions to brittle deformation such as tension cracks and the formation of aa clinker. They also recorded the apparent temperatures at which flow fronts of different dimensions stopped advancing, inflation occurred and new breakouts emerged from the front or margins of flows. Surface temperatures during the transition from channel to tube flow through regressive crustal formation were also determined. Methods of converting apparent temperatures to surface temperatures using appropriate lab-based emissivities and atmospheric attenuation have been made, and these are compared with similar transitions on basaltic flows on Etna. These then allow surface heat loss, core cooling and down-flow (temperature-dependant) rheological changes to be calculated. These are compared with similar transitions, cooling rates and rheological models for basaltic flows on Etna. The advantage of high frame rate thermal images is that they allow complete thermal characterisation of entire flows allowing crossflow and downflow temperature distributions to be determined and compared with theoretical values. Natural tracers on the surface of the flows allows velocity profiles to be constructed, and this enables the range of temperatures and strain rates at which different surface textures develop on different lava flows to be established.
DE: 8419 Eruption monitoring (7280)
DE: 8429 Lava rheology and morphology
DE: 8494 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting