STREVA will bring together researchers from universities, research institutes and volcano observatories, to explore methods for reducing the negative consequences of volcanic activity on communities. We will work both with communities facing volcanic threats and with those responsible for monitoring, preparing for and responding to those threats. Our main partners are volcano monitoring agencies and observatories in Colombia, the Caribbean and Ecuador, and through them, disaster managers and disaster researchers throughout the region, as well as residents of communities at risk. We will use a number of techniques to build links between the project and the wider community, including workshops, running scenario exercises, and using social media to report our results. Our aim, by working collaboratively across different disciplines, is to develop and apply a risk assessment framework that will generate better plans to reduce the negative consequences of volcanic activity on people and assets. Volcanic risk is a complex problem, which we shall understand by investigating a number of volcanoes, at-risk communities, emergencies and policy responses across the region. These case studies will help us to identify common issues in volcanic disaster risk and ultimately develop regional risk assessment processes. These will be crucial for long-term planning to reduce exposure to volcanic hazards. The countries in which we will work are all middle income and face multiple volcanic threats, often in close proximity to large towns and cities. The main focus will be on six volcanic sites across the Lesser Antilles, Ecuador and Colombia. We will begin the project by reviewing the secondary literature on three well monitored and active volcanoes, to analyse what has already been done to understand and reduce risk to the surrounding population. Through in-depth empirical research in these volcanic areas we shall begin to develop, test and apply our new risk assessment framework and methods for application. We will then take these lessons and apply them to three high-risk volcanoes where monitoring and understanding is less advanced. STREVA's work will generate improvements in: (i) methods for forecasting the start of eruptions and changes in activity during eruption; (ii) prediction of areas at-risk (the "footprint") from different volcanic hazards; (iii) understanding of the factors that make people and their assets more vulnerable to volcanic threats; (iv) understanding of institutional constraints and capacities and how to improve incentives for risk reduction By the end of the project, our new knowledge will help us to measure volcanic risk more accurately and monitor how that risk is changing. The practical results will be a strengthening in the capacity of stakeholders at different scales (staff in volcano observatories, local and national governments and NGOs) to produce risk assessments for high-risk volcanoes and use them to improve preparedness and response to volcanic emergencies and build resilience in the surrounding communities through long-term planning. In adopting this approach, STREVA will have real impacts in real places, and will significantly advance the fields of volcanic risk analysis and disaster risk reduction.

Continuous physical processes pervade every aspect of our society, industry and the natural world. From the flow of air over an aircraft to the propagation of mobile phone signals, to the behaviour of chemical components at every point of the manufacturing processes, continuum mechanics is at the heart of our industrial processes. In medicine, the electrical behaviour of the heart and brain, the flow of blood and other fluids through the body, and the detection of disorders using all manner of scanners and detectors are all continuum mechanics processes. In the natural world, detecting and understanding the movement and composition of the Earth enable us to understand earthquakes and to hunt for valuable minerals, while advanced understanding of the complex interaction of fluids and electromagnetic fields allows us to understand stars, the cosmos and our place in it. In all of these cases and many more beside, the mathematical equations describing phenomena are known, but solutions very rarely exist. Science and engineering are essentially dependent on computer simulation to understand any of these systems, and to design the devices and processes which use them. Many of these phenomena are so complex or have such a range of spatial scales that existing petascale computer systems are a limit on scientific advance. In addition, there is a need to go beyond mere simulation to simulate the uncertainty in processes, find the optimal solution, or discover the multiple possible outcomes of a system. The advent of exascale computing presents the opportunity to address these limitations. However, increasing computational scale, increasingly complex simulation algorithms, and the vast quantities of data produced by exascale computing will defeat not just existing simulation software, but also existing ways of writing simulation software. Gen X is a project to establish the requirements for exascale simulation software for continuum mechanics, and to provide a concrete way of achieving this capability within the next five years. The Gen X approach is to move beyond just writing code to a system of specialist simulation languages which enable scientists and engineers to specify the problem they want to solve and the algorithms they want by writing mathematics, the language of science. The actual code will be automatically generated by specialist compilers rather than hand-written. Rather than an algorithm developer writing a paper about their new development and hoping that simulation scientists will find the time to code it up for their specific problem, the algorithm will be encoded in a domain specific language and implemented in its compiler. The simulation scientist will then be able to access the algorithm directly without recoding. At exascale, writing all the simulation outputs to disk for later analysis is impossible. Instead, simulation data must be processed, analysed and visualised as the simulation is conducted, and only the results stored for later use. Gen X will provide mathematical languages for this process which will enable the scientist or engineer to concisely specify the analysis to be performed, and to have confidence that the resulting calculations will be both efficient and correct. By enabling scientists and engineers to work at a higher mathematical level while also accessing more sophisticated algorithms and hardware-specific implementations than previously possible, Gen X will make simulation science both more capable and more productive. In this manner, Gen X is essential to realising the potential of exascale computing while also making the most efficient use of research resources.

Systems modelled by partial differential equations (PDEs) are ubiquitous in science and engineering. They are used to model problems including structures, fluids, materials, electromagnetics, wave propagation and biological systems, and in areas as varied as aerospace, image processing, medical therapeutics and economics. PDEs comprise a forward model for predicting the response of a system, but are also a key component in the solution of inverse problems, for design optimisation, uncertainty quantification and data science applications, where the forward computation is repeated many times with different inputs. The numerical simulation of complex systems modeled by PDEs is a challenging topic. It involves the choice of underlying equations, the selection of suitable numerical solvers, and implementation on specific hardware. Over the decades numerous software libraries have been developed to support this task. But adapting these libraries to the specific model and combining the various components in a low-level high-performance programming language requires a major development effort. This required effort has become significantly more challenging with the advent of heterogeneous mixed CPU/GPU devices on the path to exascale systems. Implementations need to be adapted for each individual device type in order to achieve good performance. As a consequence, developing new simulations at scale has become an ever more costly and time-intensive task. In this project we propose a different simulation paradigm, based on the use of high-productivity languages such as Python to describe the problem, and automatic code generation and just-in-time compilation to translate the high-level formulations into high-performance exascale-ready code. Based on the experience with the component software libraries Firedrake, FEniCS and Bempp, the investigators will build a toolchain for complex exascale simulations of PDEs on unstructured grids, using state of the art finite element and boundary element technologies. The research will include mathematical and algorithmic underpinnings, concrete software development for automatic code generation of low-level CPU/GPU kernels, high-productivity language interfaces, and the application to 21st century exascale challenge problems in the areas of battery storage systems, net-zero flight, and high-frequency wave propagation.

The Greenland Ice Sheet (GrIS) has been losing mass over the past three decades and is now a significant contributor to global sea-level rise. In recent decades, the ice sheet's rate of mass (or ice) loss has accelerated, driven by a warming climate and substantial increases both in: 1) the flow speed and retreat rate of many large glaciers that drain the ice sheet and terminate in the ocean; and 2) the surface melt rates and area of the ice sheet experiencing summer melting. However, a critical area of future potential dynamic change and ice-mass loss, which is unaccounted for in our current model projections of the Greenland Ice Sheet's future evolution, concerns the influence of ice-marginal (or proglacial) lake formation on the dynamic stability of outlet glaciers. It is well known from numerous observations elsewhere, that glaciers which terminate in proglacial lakes typically flow much faster than similar sized glaciers that terminate on land. It is now also clear that the number and size of proglacial lakes around the margins of the GrIS are increasing and that trend will continue in to the future. There is therefore the clear potential for the development of more lake-terminating glaciers affecting the ice-sheets' ice-dynamics and long-term stability with the possibility of a dramatic (or 'catastrophic') acceleration in ice-mass loss from these hitherto slowly changing ice-margins. Greenland's land-terminating ice-sheet margins currently flow rather slowly (~100 m/yr) and their mass loss is controlled almost entirely by surface-melt processes. Since the climate is warming, these land-terminating glaciers are thinning and retreating slowly. However, in numerous glaciated regions around the globe, glacier termini are accelerating (by a factor of 2 or more) where glaciers terminate in lakes as opposed to adjacent land-terminating glaciers. This occurs because when a glacier terminates in a lake, it experiences processes which lead to glacier calving, thinning and acceleration. These processes lead to enhanced ice mass loss from the terminus calving and retreat but also through the glacier acceleration which brings ice more rapidly from higher to lower elevations on the ice-sheet thereby exposing the ice to warmer temperatures that promote increased surface melt. As such, a rather simple change in glacier terminus morphology can have a dramatic impact on the glaciers' ice dynamics and mass loss. This project will determine the extent to which these developing proglacial lakes will impact future ice-sheet mass loss, and thus contribute to sea-level rise, over the coming century. We have already undertaken a proof-of-concept study revealing contrasting behaviour at two adjacent lake- and land-terminating glaciers in SW Greenland. Using satellite data to derive glacier velocities, our study shows that ice-motion at the lake-terminating margin more than doubled between 2017-2021 (to ~200 m/yr); by contrast, the neighbouring land-terminating glacier decelerated over the same time-period. We now aim to determine the extent to which these observations of recent acceleration are typical at Greenland's numerous lake terminating margins and more importantly, investigate how important ice-marginal lake terminating glacier dynamics will become in the future for ice-sheet mass loss. In order to achieve this broad aim, the project will use a range of satellite data in conjunction with surface mass balance and ice-sheet modelling to determine: i) how glacier terminus position, motion and surface elevation have changed, both at the ice-margin and inland, in recent decades in response to glacier termination in proglacial lakes; ii) what processes are driving these observed changes in terminus behaviour; and iii) the impact of proglacial lake-induced ice-margin acceleration, thinning and retreat, on the Greenland Ice Sheet's sea level rise contributions, under projected climate warming over the next century.

Every now and again on Earth a huge volcanic eruption takes place, one much bigger than any that have been experienced by mankind. These have been termed explosive 'super-eruptions'. The most recent really big one was about 75,000 years ago in Sumatra (Indonesia) but previously there were even larger ones than that. They are quite rare, but are the large-scale end of the spectrum of volcanic activity on our planet. They have been quite newsworthy of late, with various programs such as BBC's Super-volcano (aired in summer 2005), based on the Yellowstone eruption about 2 million years ago. These eruptions produce thousands of cubic kilometers (km^3) of magma (molten rock from under the Earth's surface) in huge explosive events that yield volcanic ash beds, more strictly called pyroclastic deposits. One basic problem is that there is so much ash produced, and it is deposited so widely by the violent explosions, that it is quite difficult to trace the products of the eruptions and assess their true size. The largest known eruptions are probably about 5,000 km^3, and the one in Sumatra is estimated to have been about 2,800 km^3 but these estimates are only very rough, and are not accurate to within about half their value. This is not surprising considering that a big eruption in our experience is really very small indeed, such as Mount Pinatubo in 1991 (5 km^3) or Mount St. Helens in 1980 (about 1 km^3)! The proposed study aims, very simply, to determine to a more precise estimate for the volume of one of these vast eruptions that took place about 4 million years ago in the Andes volcanic arc of North Chile. One reason to choose this particular eruption is that the deposits are quite well preserved in the dry, high Atacama desert. Another reason is that this eruption has received some earlier study, including some past work by the Principal Investigator, and it is well enough known to be able to say that it is in the 'Top 5' of the world's largest eruptions, as assessed by a recent survey. However, the various estimates that have been made of its volume, and the way that they have been made, suggest that it could be much larger than presently envisaged. We will use techniques that have not been applied before, including making accurate digital elevation models and mapping the deposits from remotely sensed (satellite) images to try to measure the extent and thickness of the two of the main type of pyroclastic deposit from this eruption. We will also use field-based measurements made directly on the deposits themselves. Another new facet is that we will try to track, for the first time, the widespread, fine volcanic ash bed that must have fallen a long way away from the eruption vents. This may add up, despite its thinness, to a considerable amount more of magma that must have been erupted, and a part that has not been included in previous estimates of the total volume. A local expert collaborator will help us locate these ash beds. Overall, our results will be of interest to anyone interested in the extremes of volcanic activity on Earth, those in the International Association of Volcanology, who are compiling a large-eruption data base, to scientists interested in the environmental impact of explosive volcanism, and to petrologists, who study how magma is generated within the Earth. Basically we want to know 'How big is big?', or at least to know how to better approach making estimates of the size of past eruptions.