3D Numerical Modelling of Large, Rapid, Violent Geologic Processes

Meteorite impacts, large long-runout landslides, volcanic collapse, submarine landslip, and the tsunamis generated when such events occur in a marine environment, are part of a family of large, rapid, violent geologic processes that have potentially catastrophic consequences. Public awareness of these phenomena is high, but our fundamental understanding of them is far from complete. This is in large part because such high-energy processes are impossible to simulate on the laboratory scale and they have been difficult and expensive to simulate numerically until now. The aim of the proposed research is to develop an advanced, 3D numerical model for simulating impacts and other violent geologic processes, and to use this model to investigate the poorly understood natural hazards of meteorite impact, large sub-aerial and sub-marine landslip, and impact- and collapse-generated tsunamis, to predict their behaviour, and ultimately to help mitigate their destructive consequences. In recent times, impact cratering has emerged as an influential process in the evolution of the Earth and life as it exists today. It is now believed that impacts caused at least one mass-extinction, the formation of the moon, and possibly created habitats for primitive life and caused the transfer of life across the solar system, via the high-speed ejection of near-surface rocks. The catastrophic role of impact cratering in Earth history and its far-reaching consequences make imperative the need to understand impacts and the hazard that they pose. However, fundamental gaps remain in our knowledge of the impact process. The vast majority of our current understanding is derived from models and experiments where the target material is uniform and the impactor strikes perpendicular to the target surface. In reality, such events are extremely unlikely to occur on Earth; oblique impacts are far more common than near-vertical impacts, and almost nowhere on the Earth can its near-subsurface be considered uniform (for example, 70% of the Earth's surface is covered by water). The effect on the cratering process of the angle of the impactor's trajectory to the target surface, and variations in the composition and strength of the target surface, are poorly understood. Laboratory experiments and preliminary modelling work suggest that both these factors may change substantially the size and shape of the crater, and the amount of hazardous, hot vaporised rock formed during an impact, but sophisticated 3D modelling is required to fully quantify the effects. In this work the necessary impact simulations will be performed to determine the environmental consequences of impacts on Earth for any size asteroid or comet, at any velocity and angle and into any type of target surface. Two other poorly understood geologic processes that are either an immediate consequence of impacts, or involve similar physical processes, are large rock avalanches and tsunamis generated by landslides or impacts. Large rock avalanches travel vast horizontal distances with only a comparatively small vertical drop in height. Their rapid movement and extensive reach makes them a significant natural hazard, despite the rarity of their occurrence. However, the physical explanation for their high mobility has not yet been ascertained, and hence no reliable model exists for predicting their behaviour. Underwater landslides and oceanic impact events can trigger a type of local tsunami with high run-up and potentially devastating consequences. However, the generation, propagation and breaking of these waves are not yet understood, which has led to wildly differing views on the hazard that these types of tsunamis pose. The model developed as part of this research will also be adapted to simulate these processes. The models will be used to investigate how large rock avalanches can travel so much further than small ones, and to reassess the landslide- and impact-tsunami hazard.