The dynamics of erupting volcanoes are highly complex, with nonlinear feedbacks and multiple eruptive states during single eruptions. Without better quantitative understanding of these processes, interpretations of geophysical and geochemical signals recorded at the surface will remain largely empirical. This programme will probe the dynamics of volcanic reservoirs, conduits and plumes, focusing on the processes that trigger changes from one eruptive state to another. It will tackle the problems synergistically at the intersections between traditional disciplines, and will involve top-level scientists from research institutes and volcano observatories in 8 countries - France, Germany, Iceland, Italy, Norway, Portugal, Sweden and Switzerland. Measurements of quantitative eruption parameters will be made at several target volcanoes using multiple ground-based and satellite-based remote sensing techniques, the instrument arrays of the volcano observatories, and analysis of eruption products using techniques of textural and chemical microanalysis. Laboratory experiments using real and analogue materials will be used to explore magma properties and extract phenomenological laws governing eruption dynamics. Robust eruption models will be developed using (i) benchmark laboratory experiments to validate the component physics, and (ii) multi-parameter datasets to seek first-order consistency between models and measurements, thereby building confidence in our quantitative understanding of the natural system. Short visits and exchange grants will enable sharing of measurement/modelling capabilities between participating institutions and will facilitate analysis of multi-parameter datasets and numerical simulations. Emerging technologies and concepts will be communicated to young scientists at open-call workshops, brainstorming meetings and training summer schools. Training courses will be published first online for free access, then as a textbook.