Towards improved forecasting of volcanic explosivity: Investigating the role of magma mixing

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10% of the world's population live within 100 km of a volcano. With the world's increasing population and stress on natural resources, volcanoes threaten more lives every day. Explosive volcanic eruptions can have devastating societal impacts on nearby populations, covering entire countries in ash, ruining crops and livestock, and cause a huge loss of human life. These eruptions can also have global effects, with the potential to impact air traffic, air quality and surface temperature. Conversely, lava flow or dome-forming (effusive) eruptions are generally less hazardous, with impacts more localised in the area immediately surrounding the volcano. The problem is that any one volcano can erupt both explosively and effusively with rapid changes in eruptive style. We currently do not understand what controls volcano eruptive style. This gap in our knowledge makes the impacts from an impending volcanic eruption very difficult to predict. For instance, with the small, but extremely disruptive explosive eruption of Eyjafjallajokull (Iceland) in 2010, while volcanologists could forecast that an eruption would occur within a few weeks, they were unable to forecast whether the impending eruption would be explosive or effusive. The ability to forecast what type of eruption will occur and how big an eruption will be would help to limit the loss of human life and reduce economic impacts by informing mitigation procedures such as evacuations. Unfortunately this goal cannot be achieved until we can determine what controls an eruption's 'explosive potential'. Most studies believe that shallow processes (<3 km) within the conduit (the magma feeder pipe) govern this transition, however recent work has suggested that deep processes (4-10 km) occurring whilst the magma is in storage (inside the magma chamber) may be key. A particularly important process is when two magmas with different temperatures and chemistries mix at depth, which occurs commonly before eruptions. The gas dissolved in a magma has a big part to play in this process, much like opening a bottle of coke once it has been shaken, but the problem is that we do not know how dissolved gasses behave as a result of magma mixing. This project will take advantage of recent analytical advances in this field. These new techniques will be applied to samples from key eruptions to understand how the dissolved gases reacted when mixed with different magmas and on what timescales these processes occurred before the eruption. The timing is critical, because if magma mixing processes can be detected by scientists monitoring a volcano (with earthquakes for example) then we may be able to forecast what type of eruption will occur based on the data from this study. Alongside this, we will also use high pressure and temperature experiments to recreate the conditions that occur before both our example effusive and explosive eruptions. This project will transform our understanding of what conditions promote more explosive eruptions. Combining the information from this study with monitoring data will help to limit the loss of life and economic damage that explosive eruptions cause.