Volcanism, is a vital factor in the Earth system. Molten silicates are a major transport agent in the differentiation and interaction of lithosphere, hydrosphere, atmosphere, and biosphere. Further, the immediate consequences of volcanic eruptions on all scales - local, regional and global - are issues of direct practical relevance to mankind as they are measured in lives, infrastructure and the environment. Volcanism is the result of a complex interplay of physico-chemical processes operating at varying efficiencies during ascent, differentiation and eruption of magma. As a result, volcanic phenomena span a range from effusive to explosive. The largest explosive events are repeatedly responsible for global impact on the Earth System, yet it is precisely these events that, due to their explosive character, are relatively inaccessible for direct scientific investigation. A major opportunity in accessing such systems has been provided by recent technological advances permitting the experimental investigation of volcanism. Experimental volcanology operates directly under volcanic conditions of time, pressure, temperature, and state; a near-unique opportunity in the solid earth sciences. Based on experimental volcanology, this project aims to provide mechanistic models of magmatic/volcanic processes and their impact on the Earth System. Four priority areas are selected as those needing most urgent attention. These are: 1) Quantification of the rheology of magma/lava for parameterisation of stress-strain relationships in numerical simulations of eruptive events. 2) Mechanistic understanding explosive failure of magma for the interpretation of volcanic hazard monitoring. 3) Development of quantitative methods for inferring eruptive physics from the physico-chemical fossil records (thermal, magnetic, chemical) preserved in volcanic lavas. 4) Experimental characterisation of the physical, chemical and biological properties and impact of volcanic ash on the earth system.