Journal of Conference Abstracts

Volcano Monitoring using Infrared Spectral Radiance Data from the ERS Along Track Scanning Radiometer

M. J. Wooster (m.j.wooster@open.ac.uk) & D. A. Rothery (d.a.rothery@open.ac.uk)

Department of Earth Sciences, The Open University, Milton Keynes MK7 6AA, U.K.

The Along Track Scanning Radiometer (ATSR) is a relatively new remote sensing instrument flown onboard the European ERS series of remote sensing satellites. ATSR has collected global-maps of infrared spectral radiance data at a spatial resolution of around 1 km for the past five years, this dataset being primarily used to produce extremely accurate estimates of global sea surface temperature. We are investigating the use of time-series ATSR data for the monitoring of effusive volcanic activity, principally at remote and poorly monitored volcanoes. Work at Lascar Volcano, Chile has indicated that ATSR data can be used to determine the status of the summit lava dome, with major changes in observed shortwave infrared spectral radiance apparently proceeding vulcanian explosive eruptions. A similar study of the 1991-1994 lava dome at Mount Unzen, Japan has produced reasonable correlations (r² > 0.5) between spectral radiance data taken by ATSR and ground-based measurements of lava effusion rate. Further techniques have been developed to estimate various lava flow thermal parameters from ATSR spectral radiance data. The accuracy of these techniques is being tested using ATSR data of the well documented 1991-1993 eruption of Mount Etna, Sicily with an ATSR time-series having already been used to study the largely unmonitored 1995 eruption of Fernandina Volcano, Galapagos Islands.

Protonation of Oxygen Sites in beta-Mg₂SiO₄

K. Wright¹ (kwright@fs2.ge.man.ac.uk), P. Sinclair² (phillip@ri.ac.uk) & C. R. A. Catlow² (richard@ri.ac.uk)

¹ Dept. of Earth Sciences, University of Manchester, Manchester M13 9PL.

² Royal Institution of Great Britain, Albemarle St., London W1X 4BS.

Wadsleyite, beta-(Mg,Fe)Si₂O₄ is believed to be a major component of the Earth's transition zone. Experimental evidence indicates that H₂O has a greater solubility in wadsleyite than in its low pressure polymorph, olivine. However, there is some debate as to which O sites in the structure can be protonated, just the O1, or both the O1 and O2 sites. In a previous study, Wright and Catlow (1996) used atomistic computer simulation techniques to model the dissolution of H₂O in Wadsleyite and proposed that only the O1 site could be easily protonated. As a follow-up to this work, we have used quantum mechanical embedded cluster methods to further probe the nature of OH defects in Wadsleyite. Our results, in agreement with the atomistic calculations, show that the O1 site has a much lower protonation energy than that of the O2 site.