NSFGEO-NERC Quantifying disequilibrium processes in basaltic volcanism

Lead Research Organisation: Durham University
Department Name: Earth Sciences

Abstract

Basaltic volcanism is the most common form of volcanism in the solar system. On Earth, eruptions can impact global and regional climate, and threaten populations living in their shadow, through a combination of ash, gas and lava emissions. The specific risk to the UK from an Icelandic eruption is recognized as one of the four 'highest priority risks' in the National Risk Register of Civil Emergencies. The impact of an eruption is determined by both intensity and style, ranging from explosive and ash-rich (impacting on air-space access and climate) to effusive and gas-rich (affecting public health and crops/livestock locally and distally). Understanding these eruptive styles, and their evolution in time and space is key to forecasting the impacts of eruptions.

Eruption style is controlled by the degree of coupling between gas and magma during magma ascent, with strong coupling leading to enhanced fragmentation and ash production. This coupling is controlled by the interplay and feedback among several non-linear processes: multi-phase magma viscosity evolution, crystallisation, gas exsolution, permeability, magma ascent velocity and fragmentation within a dynamic magma plumbing system. Such non-linearity produces complex behaviour. Understanding the processes controlling eruptive style is therefore critical for volcanology and eruption forecasting.

A crucial limitation of previous work is that it has been predicated almost exclusively on the assumption of equilibrium between melt, crystals and volatiles. In other words, the volcanology community has conventionally assumed that the processes of magma degassing and solidification/crystallisation occur nearly instantaneously in response to depressurisation during magma ascent and eruption. However, it is now recognised that the timescales required to achieve equilibrium for both crystal growth and volatile exsolution are similar to or longer than ascent times for erupting basaltic magmas, and therefore disequilibria are ubiquitous. Disequilibrium processes are therefore a key missing link preventing quantitative modelling and understanding of volcanic processes, and their impacts.

The core aim of the NERC-NSF DisEqm project is to create an empirically-constrained quantitative description of disequilibrium processes in basaltic volcanism, and to apply this to address key volcanological problems through a new numerical modelling framework

In order to meet this aim, we bring together a world-leading team to perform experiments using new, ground-breaking synchrotron X-ray imaging and rheometric techniques to visualise and quantify crystallisation, degassing and multiphase, HPHT (high-pressure, high-temperature) viscosity evolution, revolutionising the fields of HPHT experimental petrology and HPHT rheometry. Geochemical constraints will be achieved by applying state of the art petrological analytical techniques to samples produced both on the beamline and in benchtop quench experiments. We will perform large-scale fluid dynamics simulations to inform and validate the 3D numerical modelling, and we will constrain fragmentation and eruption column processes with empirical field studies. Results will be integrated into a state-of-the-art numerical model, and applied to impact-focussed case studies for Icelandic, US and Italian basaltic eruptions. In conclusion, our project will produce a paradigm shift in our understanding of disequilibrium processes during magma ascent and our capacity for modelling basaltic eruption phenomena, creating a step-change in our ability to forecast and quantify the impacts of basaltic eruptions.

Planned Impact

Volcanic eruptions are one of the four 'highest priority risks' identified in the UK's National Risk Register of Civil Emergencies. The UK's risk management strategy focuses on acquiring numerical models that will allow evidence-based judgements to be made; in particular whether it is safe to fly. The DisEqm project is aimed at obtaining a step-change in the accuracy of such models by including the disequilibrium processes that represent fundamental controls on magma ascent and eruption and are absent from existing models. Our model will be the most advanced tool available for assessing volcanic eruption hazard.

The DisEqm project will be guided by a Steering Committee chosen to interface between science, policy and industry and includes members from the UK Met Office, Icelandic Met Office, University of Iceland, BGS, USGS and INGV. DisEqm PIs in conjunction with these stakeholders will use the model to define and evaluate likely eruption scenarios of Icelandic, Italian and US volcanoes. The results will be communicated in a joint report by the Consortium and Steering Committee to policy markers including the UK Cabinet Office, BGS, USGS and INGV. We expect that the DisEqm project will have a direct impact on policy in the UK and the other countries (Italy, Iceland, US) and in assessing risk of volcanic eruptions. This will affect the UK population as a whole by refining and improving both the quality of possible eruption scenarios, and also assisting policy makers with a well-tested volcano model during future eruptions.

We will reach out to researchers with responsibilities for hazard assessment and policy development in other regions by inviting them to a 2-day Knowledge Transfer Workshop on 'Basaltic Eruption Hazard Forecasting'. We will in this way make our numerical modelling tool available globally as well as the technological innovations and experimental and field data. We will at this Workshop seek to initiate new collaborations so that we can apply our methods to scenarios in other countries. Thus we expect the impact will ultimately have global reach.

Relevant equipment manufacturers are also represented on our Steering Committee. The innovations in HPHT visualisation technology that we will be driving forward in the DisEqm are of direct relevance to them. By working with them directly from the outset, we can mitigate risk and ensure a successful completion of the project as well as maintain an immediate route to commercial exploitation of the technological advances.

We will facilitate wider exploitation of the technological advances via a 2-day Knowledge Transfer Workshop on '4D Visualisation' that will focus on the methods used to obtain information of evolving textures in space and time under HPHT conditions. We will invite delegates from cognate disciplines (e.g. the aerospace industry) who will be interested in the new methods we are developing. Thus DisEqm project outputs will impact on other disciplines

The compelling visualisations of 3D magma ascent and 4D tomography will make the project outputs perfectly suited for public engagement. All PIs - and, by extension, their staff - are involved in public outreach and science education broadly as a matter of course in their work. Involvement with the DisEqm project will enhance their outreach and education activities. A specific, new public outreach opportunity that we will develop is to collaborate with the new London-based GeoBus venture. This will impact on science teaching in many schools thereby inspiring new generations of scientists and non-scientists alike.

The DisEqm project has an equal distribution of male and female PIs, which is unusual in this discipline. The gender balance will not only help to provide strong role models for more junior staff within DisEqm but will be visible externally within the wider scientific community.

Publications

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Description We have run experiments that show how magma convects in the plumbing system underneath a basaltic volcano. We have found that the convection is sometimes well-organized (into upwelling and downwelling regions) so that it's easy for magma to get to the surface, but is sometimes chaotic, which slows down magma ascent.
Exploitation Route The findings will help people to determine how long basaltic fissure eruptions might take to form well-localized vents.
Sectors Environment