Volcanoes frequently affect our lives and thus have been studied since people started living and farming on their nutrient-rich, ash-covered flanks. The processes that cause eruptions also control the compositions and volumes of erupted material and ultimately the eruption styles. These processes and the time scales at which they operate are not well understood. Part of the reason is that many processes controlling eruptions occur in magma reservoirs deep below the volcano. These reservoirs are not easily accessible until they are solidified forming plutons and exposed millions of years later, when volcanic cover rocks are removed through uplift and erosion.The proposed study will, for the first time, integrate research on a fully exposed magma plumbing system in Colorado, USA. Here, volcanic materials are juxtaposed with their plutonic equivalents. The broadly educated applicant, who has carried out field, geochronology and geochemistry studies of plutons in the USA, is teaming up with the host, who has focused his research on volcanic rocks worldwide. The idea is to converge their respective expertise and conduct an interdisciplinary, multilevel analytical study on both volcanic and plutonic rocks. Research will commence with field work, petrographic studies and determination of relative ages. The main element of this study employs novel mineral-scale analyses of crystals from both rock types. The recovery of geochemical information from single crystals, in particular, will be used to provide a record of the processes and timescales operating during magma evolution. The host institution at Durham University has built a state-of-the-art geochemical laboratory for single mineral studies where such detailed crystal scale information recorded during crystal growth can be deciphered. This international study is designed to enhance scientific exchange between the UK and USA, the quality of research and results, and to improve mutual training in the respective fields.