Lava Dome Collapses : Their Mechanisms and Short-Term Forecasting
Calder, Eliza Principal Investigator
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Lava domes are piles of viscous magma that, in essence, form bulbous plugs on top of volcanic vents. They grow slowly as partially solidified magma is squeezed up the volcanic conduit, and they can host high internal pressures as gases exsolving from the magma try to escape. Lava dome eruptions are notorious for they often suddenly transformation from being benignly effusive to violently explosive. Sudden removal of these plugs, either by vertically-driven explosions, caused once the internal gas pressure exceeds the tensile strength of rock, or sudden collapse and spontaneous disintegration as the piles grow and become unstable, can have devastating consequences. These collapse events spawn one of the major hazard in volcanology; devastating pyroclastic density currents, which move down the flanks of the volcano at speeds of up to 60 m/s. This project concerns the improved understanding and forecasting of lava dome collapses and has immediate and practical applications pertaining to the management of several on-going volcanic crisis. The work will be based on the Soufrière Hills volcano (SHV) eruption, Montserrat, combined with preliminary comparative studies from two other active lava dome eruptions, Mount St Helens, USA, and Santiaguito, Guatemala. Such eruptions occur with relative frequency, are potentially extremely destructive and can continue for years-to decades. The real merits therefore, will be reaped when relationships unearthed during this study are usefully and successfully applied to dome forming eruptions elsewhere. The fundamental objective of this work is to stringently quantify aspects of activity associated with lava dome failure and collapse including information on the timing and location of rockfalls and pyroclastic flows, as well as the nature of other precursory activity. The project will address three issues that require further attention: differentiating failure modes; identifying structural controls; and treating collapses as part of a continuous process of mass wasting rather than discrete independent events. By investigating along these themes, this work will validate existing models and constrain a number of current limitations. The results of this work will provide the basis from which statistically-driven models can be developed, in order to construct a short-term forecasting model of mass wasting at lava domes. The novelty and impact of this study hinges on: Innovative techniques for comparing disparate data sets of monitoring data, and the generation of an important record of dome activity that will be useful to the volcanological community; Understanding continuous growth and wasting processes allowing assessments to be made about physical mechanisms but also providing a basis for testing statistical models (the quality of which is enhanced by collection of large data sets); The fusion of data from digital elevation models, thermal images, and gas plume maps, developing a truly integrative approach to understanding dome instability.