Volcano-Climate Interactions in the Holocene

Efforts to understand the complex interactions between distinct earth systems are a vital part of the future of Earth Science. Recent advances in glaciology, atmospheric sciences, and natural hazard modelling have highlighted how variations in separate components on both a local and global scale can affect adjacent systems. Volcanic hazards have been demonstrated to be susceptible to external hydrological and cryospheric influences. It has previously been hypothesised that regional-scale changes to pressure regimes, such as might occur following rapid deglaciation leading to isostatic uplift, might be sufficient to cause widespread changes in eruption frequency in volcanic areas. This theory is often referred to as the ‘unloading effect’. Icelandic volcanic ash can be found in sites across western mainland Europe and the UK, preserved as tephra layers in terrestrial, lacustrine, and marine sediments. These layers provide temporal and geochemical information on the source eruption, and may also be used as a measure of the frequency of explosive eruptions (the most likely to disperse ash over a wide geographic area). However, as tephrochronology is a relatively new discipline, the methodologies and related applications are still in the process of development. This thesis addresses concerns related to the preservation potential and the impacts of commonly used chemical extraction methods of volcanic tephra. This is achieved through laboratory experimentation, EPMA analysis, and statistical evaluation performed on volcanic glasses of various compositions. Additionally, this thesis presents an updated and expanded database of Holocene and Late Glacial tephra in Europe. The final chapter builds on this database in addition to incorporating palaeo-atmospheric and -glacial modelling to evaluate the potential of the unloading effect in Iceland within the last 12,500 years, finding that, while evidence for this effect occurring within the Holocene does exist, it is likely to be a secondary factor in determining eruption frequency.