Bubble, burp, bang! Big experiments in volcanic physics

Basaltic volcanoes produce a wide spectrum of eruption types, from passive outgassing, through effusion, spattering, and fountaining of lava, to the explosive production of ash. The nature of the eruption - and therefore of the hazard that it poses - is shaped mainly by processes that take place out of sight, in the sub-volcanic plumbing system. Scaled laboratory analogue experiments provide a window into this plumbing system, allowing us to identify and characterize the fluid dynamic processes that occur, and link them to eruption style. I will present the results of analogue experiments performed at a range of scales. The experiments reveal a rich diversity of multiphase fluid dynamic phenomena, and demonstrate that a critical control on eruptive style is the degree to which gas and magma become separated during ascent: when gas and magma are well coupled, effusive activity is favoured; when gas separates from, and rises through the magma, more impulsive or explosive activity results. The spectrum of eruption types, therefore, represents the surface expression of diverse multiphase fluid dynamic processes that occur in the volcanic plumbing system