Monitoring gases from andesite volcanoes

Monitoring gases from andesite volcanoes for hazard mitigation or scientifi c enquiry is complicated by the wide range of eruption styles. Monitoring i s aimed at both measuring the rates of gas emission, and changes in their c ompositions. Direct sampling techniques are restricted to accessible vents, and are unsuitable for syn-eruption monitoring. Correlation spectroscopy i s a simple and robust method for measuring emission rates of sulphur dioxid e! but is subject to large errors. Open-path Fourier transform spectroscopy provides a remote method for determining plume gas compositions, hut requi res careful atmospheric radiative transfer modelling. Few andesite volcanoe s have been consistently monitored. Published data show that there is no si mple general model for Volcano degassing: each volcano, and each eruption, presents separate problems, many of them arising from the evolving interact ion between magmatic and hydrothermal systems during an episode of activity Because of its lower solubility in magmas and conservative behaviour in hy drothermal systems, remote measurements of carbon dioxide proportions and e mission rates would be extremely valuable for monitoring, but they remain d ifficult because of its high atmospheric concentration.