Magmatic Processes and Eruption Variability at Mount Taranaki, New Zealand. Main Supervisor: Professor Heidy Mader (University of Bristol) Co-­‐Supervisor: Dr Richard Brooker (University of Bristol) Co-­‐Supervisor (CASE Partner): Dr Geoff Kilgour (GNS Science, New Zealand) Project Enquiries: [email protected] Host Institution: University of Bristol Background Mount Taranaki belongs to a class of volcanoes that experience repeated switches in activity between dome-­‐forming extrusion of highly-­‐viscous andesitic lava and explosive activity. This type of behaviour is common for andesitic volcanoes; other examples are Mount St Helens, Montserrat, Bezymianny, El Chichon, Merapi. The switch to explosive activity can be very sudden and the ensuing pyroclastic flows and plinian eruptions are highly hazardous. Understanding what controls the sudden transitions is a central but still open problem in volcanology. Mount Taranaki has experienced several cycles of lava dome formation, dome collapse and explosive (often sub-­‐plinian) phases. In this project, the student will use Mount Taranaki as a case study to explore the physical and chemical evolution that leads to the transition. Research to-­‐date on this volcano consists of several field-­‐based studies that have considered the petrology, bulk rock geochemistry and textures in the eruptive products of some episodes. Project Aims and Methods In this project, the student will combine field observations, laboratory studies and modelling to investigate the magma storage conditions and the physico-­‐chemical processes driving degassing and crystal growth prior to and during eruptions at Taranaki. The aim is to quantify how the magma evolves as it rises from depth and hence what controls the observed switches in eruption style. Laboratory work will consist of a combination of petrological and textural studies of field samples, high pressure laboratory experiments to identify the conditions required to produce the observed phases and melt evolution, and also rheological measurements of analogue (i.e. non-­‐magmatic) suspensions with similar assemblages of bubbles and crystals. From this information and using recently development methods (e.g. Kilgour et al in review, Mader et al 2013) the student will determine the source conditions of the magma and then how it evolves during its ascent from depth to eruption at the surface. The student will spend at least one (and possibly two) periods of time (totalling a minimum of 3 months) based at GNS Science, New Zealand, to conduct the field observations and some of the associated analyses. Candidate The project would suit a student with a first degree in the physical sciences and a desire to develop a range of different skills (field, lab and modelling). The balance between field, laboratory and numerical modelling can be adjusted to suit the background and interests of the candidate. Case Award This is a CASE award. The student will spend a minimum of 3 months at the CASE Partner, GNS Science (New Zealand). An existing CASE PhD Student has spent considerably longer at the CASE Partner than this. Dr Kilgour visits Bristol periodically and we maintain contact via a monthly skype with him that usually includes the whole team (i.e. the PhD student and Bristol supervisors). Training The student will receive training in volcanology and advanced field skills, based at GNS Science (http://www.gns.cri.nz/), New Zealand. Petrology, geochemistry, textural studies, rheological experiments and modelling will be completed at Bristol. Candidates will emerge with a strong background in the physical Earth sciences including advanced field, laboratory and modelling skills and highly marketable transferable skills including: numeracy, written and spoken presentational skills and an ability to work in a multidisciplinary team. Previous PhD graduates have gone on to successful careers in academia, environmental organisations (such as the Met Office or British Antarctic Survey) and commercial consultancies, volcano monitoring, and teaching. References • Kilgour, Mader, Blundy and Brooker (2015) ‘Rheological controls on the eruption potential and style of an andesite volcano: a case study from Mt Ruapehu, New Zealand.’ Journal of Volcanology and Geothermal Research (in review). • Mader et al (2013) ‘The rheology of two-­‐phase magmas: A review and analysis.’ Journal of Volcanology and Geothermal Research, 257, 135-­‐158, doi:10.1016/j.jvolgeores.2013.02.014. • Turner et al (2011) ‘Relating magma composition to eruption variability at andesitic volcanoes: A case study from Mount Taranaki, New Zealand.’ GSA Bulletin 123(9/10), 2005-­‐2015, doi:10.1130/B30367.1. • Platz et al (2007) ‘Transition from effusive to explosive phases in andesite eruptions – A case-­‐study from the AD1655 eruption of Mt Taranaki, New Zealand.’ Journal of Volcanology and Geothermal Research 161, 15-­‐34, doi:10.1016/j.jvolgeores.2006.11.005.