The flow of crystal-bearing magmas.

Lead Research Organisation: University of Bristol
Department Name: Earth Sciences


Many volcanoes erupt magma slowly and non-explosively for a long period of time. The magma is often piled up as a 'dome' that sits at the top of the volcano. It is quite common for the eruption at such volcanoes suddenly to switch to a highly-explosive type of eruption, which is much more dangerous. At the moment we cannot predict accurately when such a switch will occur, which is a problem for the people who live near such volcanoes. We now think that the switchings are caused mainly by effects of crystals growing in the magma. The crystals make the magma more viscous, that is, more 'sticky', so it doesn't flow so easily. The magma becomes rigid and forms a plug which blocks the path for the rising magma. The blockage causes the pressure to rise in the volcano. Eventually, the pressure becomes so great that the plug is destroyed and a violent explosion occurs. If we want to be able to describe this process accurately, then we need to know how crystals in the magma change the way the magma flows. The project that we are planning here will address this problem. We will conduct a series of laboratory experiments in which we will produce mixtures of solid particles (in place of crystals) in a liquid. We will measure the viscosity of these mixtures (i.e. how easily they flow or how 'sticky' they are) using an instrument called a 'rheometer'. The particular rheometer we will use has a microscope attached to it, so we will be able to see how the particles are moving. It is particularly important to be able to see this because the particles move around as the mixture flows. As the particles move, they sometimes line up, or form clumps and this affects the viscosity. We think it will be important to see what is happening to the particles inside the mixture as it flows so that we can relate this to the measured viscosity. We will use the results of the laboratory experiments to produce equations that describe the viscosity of the mixtures so that it will be possible to calculate the viscosity of the particle/liquid mixture, rather than measure it. This is interesting because, if we manage to do this, we will have understood something new about the way magma flows. We will then use the equations we have produced to calculate the viscosity of a magma that contains crystals in computer models that try to predict how magmas erupt and especially the switchings from slow, non-explosive to violent, highly-explosive eruptions. This will allow us to see what controls the behaviour and, will help to make the outputs from the numerical models useful for the prediction of volcanic eruptions.


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Mader H (2013) The rheology of two-phase magmas: A review and analysis in Journal of Volcanology and Geothermal Research

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Mueller S (2009) The rheology of suspensions of solid particles in Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences

Description We have developed a constitutive equation for particle suspension consisting of a Newtonian liquid with particle contents up to 70vol%. The constitutive equation allows for particle shape and bimodal particle size distributions. We have applied the constitutive equation to magmatic flows. The review article summarises the output of this work and similar work on bubble suspensions, i.e. on two-phase suspensions.
Exploitation Route The research is relevant in many areas outside physical volcanology as particle suspensions are ubiquitous in the commerical sectors (e.g. the food industry, cosmetics and also the oil industry). The paper published in the Proceedings of the Royal Society has been widely cited by researchers in many areas of science and engineering. The constitutive equation will be of use in numerical models of flows of suspensions. Such models are of use within physical volcanology as exploration tools to study volcanic flow behaviour and also in eruption forecasting. Suspension flow models are also used in commercial settings to constrain production processes.
Sectors Agriculture, Food and Drink,Chemicals,Environment,Other

Description This research has lead to some key new findings regarding the rheology of particle suspensions which is a topic of widespread interest within science and technology. The publication in the Proceedings of the Royal Society has been highly cited by researchers from many disciplines across science and engineering. The research is also significant for modelling of volcanic processes and the outputs are being used by modellers employed in managing volcanic emergencies.
First Year Of Impact 2010
Sector Agriculture, Food and Drink,Chemicals,Environment,Other
Impact Types Policy & public services

Description INGV 
Organisation National Institute for Geophysics and Volcanology (INGV)
Country Italy 
Sector Public 
PI Contribution Invitation to speak at workshop on modelling. Ongoing collaborations with Mike Burton and Margherita Polacci. Involvement with Burton's ERC grant which included participation in experimental research at Durham (fully-funded through Burton's ERC grant). Now Project Partner on DisEqm Large Grant - we are contributing constitutive equations for use in the numerical models that are being developed at INGV.
Collaborator Contribution Organisation of workshop. ERC grant funding. Contribution to research effort and publications. Now Project Partner on DisEqm Large Grant - numerical modelling of volcanic flows.
Impact No outputs as yet on DisEqm grant. Multi-disciplinary: physics and chemistry of materials, geology, volcanology, rheology, numerical modelling of multiphase flows
Start Year 2007