Numerical modelling of large impact crater collapse
File(s)
Supplementary material
Author(s)
Collins., Gareth S.
Type
Thesis
Abstract
This thesis addresses the important geologic question of how large impact craters are formed. The approach of the research described in this thesis has been to study impact crater formation using the only feasible method of simulating such a rarely occurring, complicated and highly dynamic process: numerical modelling. The numerical model described in this thesis simulates the gravitationally driven collapse of a transient cavity, which is generated during the early stages of an impact event. To facilitate collapse, the rheologic properties of the material surrounding the crater must, be modified significantly from the typical material properties of rock. This is achieved using acoustic fluidization; where strong vibrations produced by the expanding shock-wave cause extreme pressure fluctuations in the target. At times and positions where the overburden pressure is sufficiently counteracted, the frictional resistance is reduced, enabling the rock debris to flow. This numerical model of crater collapse is first used to develop a predictive, quantitative model for the collapse of a Chicxulub-scale impact crater. This is achieved by testing and refining the model until the simulations produce a collapsed crater that contains most of the features observed in the seismic data obtained at Chicxulub. The model is also extended to simulate the formation of large impact craters on the Moon. A generic model for the formation of peak rings in large impact craters is developed. During the simulations material that is originally part of the central uplift collapses outward and is thrust over the inwardly-collapsing transient crater rim to form a concentric, topographic feature inside the final crater rim. This model for peak-ring generation has not been previously demonstrated by numerical simulations and predicts that the peak ring is composed of deeply derived material, and that the stratigraphy within the peak ring is overturned.
Date Issued
2002
Date Awarded
2002-01
Copyright Statement
Creative Commons Attribution NonCommercial NoDerivatives Licence
Advisor
Warner, Mike
Morgan, Jo
Publisher Department
Earth Science and Engineering
Publisher Institution
University of London - Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)