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Volcano research in the School of Geosciences is undertaken by a number of staff spread across the department and covers many aspects of volcanology. A selection of current research fields is presented below.
Magma fragmentation and explosive eruptions
Explosive eruptions produce pumice and ash that are dispersed around the volcano. Fragmentation is controlled by magmatic gases and by the interaction of erupting magma with external water (e.g. from a lake or glacier). Different fragmentation processes result in different grainsize distributions, pumice densities and ash grain shapes. These can be studied by techniques such as field mapping, sieving, laser particle size analysis, and Scanning Electron Microscope (SEM) using facilities within the department. Understanding the proportion of fine ash (<63 microns diameter) generated during explosive eruptions is important because fine ash remains airborne for longer, leading to widespread dispersal and presenting more of a hazard to aviation. Extremely fine ash (<10 microns diameter) has been associated with lung damage.
Lava flow emplacement during effusive eruptions
Lava flows produced by effusive eruptions are slow-moving, but have potential to destroy property and infrastructure within their path. The emplacement mechanism of a lava flow is controlled by parameters such as effusion rate, lava viscosity and underlying gradient. The emplacement mechanism controls how heat is lost from flowing lava; a key control in how far it can eventually flow. Study of both modern and ancient lava flows helps us understand these processes. Large eruptions of basaltic lava, such as the 1873-4 eruption of Laki, Iceland, are also associated with the release of large quantities of volcanic gases.
The fate of gas dissolved within a magma is a key parameter in determining the explosivity of an eruption. During explosive eruptions, expanding gases trapped within bubbles in the magma accelerate the mixture towards the surface and drive fragmentation into pumice and ash. By contrast, if the gas is able to escape, an effusive eruption results and a lava flow is produced. Furthermore, dissolved magmatic gases such as SO2 have important climatic and health impacts. The gas content of a magma at different stages of an eruption can be determined by microprobe analysis of melt inclusions and volcanic glass.
Tephrochronology is a dating technique based on the presence of volcanic ash. Volcanic ash (tephra) from Icelandic is found in peat bogs and lake cores across northern Europe. If the source eruption is known, then the presence of ash indicates the age of a deposit; this information is extremely valuable in archaeology and paleoclimate. Geochemical analysis (often via Electron Probe Microanalysis) is necessary to link tephra grains to particular eruptions and a database is being created allowing easy identification of unknown tephras. Furthermore, analysis deposits of tephra from the recent Eyjafjallajökull 2010 and Grímsvötn 2011 eruptions within the UK indicates the relative amounts of tephra deposited by eruptions of known size.
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