108 results found
Davison TM, Derrick JG, Collins GS, et al., Impact-induced compaction of primitive solar system solids: The need for mesoscale modelling and experiments, Procedia Engineering, ISSN: 1877-7058
Primitive solar system solids were accreted as highly porous bimodal mixtures of mm-sized chondrules and sub-μm matrix grains. To understand the compaction and lithification of these materials by shock, it is necessary to investigate the process at the mesoscale; i.e., the scale of individual chondrules. Here we document simulations of hypervelocity compaction of primitive materials using the iSALE shock physics model. We compare the numerical methods employed here with shock compaction experiments involving bimodal mixtures of glass beads and silica powder and find good agreement in bulk material response between the experiments and models. The heterogeneous response to shock of bimodal porous mixtures with a composition more appropriate for primitive solids was subsequently investigated: strong temperature dichotomies between the chondrules and matrix were observed (non-porous chondrules remained largely cold, while the porous matrix saw temperature increases of 100’s K). Matrix compaction was heterogeneous, and post-shock porosity was found to be lower on the lee-side of chondrules. The strain in the matrix was shown to be higher near the chondrule rims, in agreement with observations from meteorites. Chondrule flattening in the direction of the shock increases with increasing impact velocity, with flattened chondrules oriented with their semi-minor axis parallel to the shock direction.
Hill J, Avdis A, Mouradian S, et al., Was Doggerland catastrophically flooded by the Mesolithic Storegga tsunami?
Myths and legends across the world contain many stories of deluges andfloods. Some of these have been attributed to tsunami events. Doggerland in thesouthern North Sea is a submerged landscape thought to have been heavilyaffected by a tsunami such that it was abandoned by Mesolithic humanpopulations at the time of the event. The tsunami was generated by the Storeggasubmarine landslide off the Norwegian coast which failed around 8150 years ago.At this time there were also rapid changes in sea level associated withdeglaciation of the Laurentide ice sheet and drainage of its large proglaciallakes, with the largest sea level jumps occurring just prior to the Storeggaevent. The tsunami affected a large area of the North Atlantic leavingsedimentary deposits across the region, from Greenland, through the Faroes, theUK, Norway and Denmark. From these sediments, run-up heights of up to 20 metreshave been estimated in the Shetland Isles and several metres on mainlandScotland. However, sediments are not preserved everywhere and so reconstructinghow the tsunami propagated across the North Atlantic before inundating thelandscape must be performed using numerical models. These models can also beused to recreate the tsunami interactions with now submerged landscapes, suchas Doggerland. Here, the Storegga submarine slide is simulated, generating atsunami which is then propagated across the North Atlantic and used toreconstruct the inundation on the Shetlands, Moray Firth and Doggerland. Theuncertainty in reconstructing palaeobathymetry and the Storegga slide itselfresults in lower inundation levels than the sediment deposits suggest. Despitethese uncertainties, these results suggest Doggerland was not as severelyaffected as previous studies implied. It is suggested therefore that theabandonment of Doggerland was primarily caused by rapid sea level rise prior tothe tsunami event.
Holm-Alwmark S, Rae A, Ferriere L, et al., Combining shock barometry with numerical modeling: insights into complex crater formation – The example of the Siljan impact structure (Sweden), Meteoritics and Planetary Science, ISSN: 1086-9379
Collins GS, 2017, Moon formation: Punch combo or knock-out blow?, Nature Geoscience, Vol: 10, Pages: 72-73, ISSN: 1752-0894
Collins GS, Lynch E, McAdam R, et al., 2017, A numerical assessment of simple airblast models of impact airbursts, METEORITICS & PLANETARY SCIENCE, Vol: 52, Pages: 1542-1560, ISSN: 1086-9379
Forman LV, Bland PA, Timms NE, et al., 2017, Defining the mechanism for compaction of the CV chondrite parent body, GEOLOGY, Vol: 45, Pages: 559-562, ISSN: 0091-7613
Kring DA, Claeys P, Gulick SPS, et al., 2017, Chicxulub and the Exploration of Large Peak-Ring Impact Craters through Scientific Drilling, GSA Today, Pages: 4-8, ISSN: 1052-5173
Muxworthy AR, Bland PA, Davison TM, et al., 2017, Evidence for an impact-induced magnetic fabric in Allende, and exogenous alternatives to the core dynamo theory for Allende magnetization, Meteoritics & Planetary Science, ISSN: 1086-9379
Rae ASP, Collins GS, Grieve RAF, et al., 2017, Complex crater formation: Insights from combining observations of shock pressure distribution with numerical models at the West Clearwater Lake impact structure, METEORITICS & PLANETARY SCIENCE, Vol: 52, Pages: 1330-1350, ISSN: 1086-9379
Rutherford ME, Chapman DJ, Derrick JG, et al., 2017, Probing the early stages of shock-induced chondritic meteorite formation at the mesoscale, SCIENTIFIC REPORTS, Vol: 7, ISSN: 2045-2322
Smith R, 2017, Numerical modelling of tsunami generated by deformable submarine slides
Submarine slides can generate tsunami waves that cause significant damage and loss of life. Numerical modelling of submarine slide generated waves is complex and computationally challenging, but is useful to understand the nature of the waves that are generated, and identify the important factors in determining wave characteristics which in turn are used in risk assessments. In this work, the open-source, finite-element, unstructured mesh fluid dynamics framework Fluidity is used to simulate submarine slide tsunami using a number of different numerical approaches. First, three alternative approaches for simulating submarine slide acceleration, deformation and wave generation with full coupling between the slide and water in two dimensions are compared. Each approach is verified against benchmarks from experimental and other numerical studies, at different scales, for deformable submarine slides. There is good agreement to both laboratory results and other numerical models, both with a fixed mesh and a dynamically adaptive mesh, tracking important features of the slide geometry as the simulation progresses. Second, Fluidity is also used in a single-layer Bousinesq approximation in conjunction with a prescribed velocity boundary condition to model the propagation of slide tsunami in two and three dimensions. A new, efficient approach for submarine slide tsunami that accounts for slide dynamics and deformation is developed by imposing slide dynamics, derived from multi-material simulations. Two submarine slides are simulated in the Atlantic Ocean, and these generate waves up to 10 m high at the coast of the British Isles. Results indicate the largest waves are generated in the direction of slide motion. The lowest waves are generated perpendicular to the slide motion. The slide velocity and acceleration are the most important factors in determining wave height. Slides that deform generate higher waves than rigid slides, although this effect is of secondary importance f
Watters WA, Hundal CB, Radford A, et al., 2017, Dependence of secondary crater characteristics on downrange distance: High-resolution morphometry and simulations, JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS, Vol: 122, Pages: 1773-1800, ISSN: 2169-9097
Baker DMH, Head JW, Collins GS, et al., 2016, The formation of peak-ring basins: Working hypotheses and path forward in using observations to constrain models of impact-basin formation, ICARUS, Vol: 273, Pages: 146-163, ISSN: 0019-1035
Davison TM, Collins GS, Bland PA, 2016, MESOSCALE MODELING OF IMPACT COMPACTION OF PRIMITIVE SOLAR SYSTEM SOLIDS, ASTROPHYSICAL JOURNAL, Vol: 821, ISSN: 0004-637X
Forman LV, Bland PA, Timms NE, et al., 2016, Hidden secrets of deformation: Impact-induced compaction within a CV chondrite, EARTH AND PLANETARY SCIENCE LETTERS, Vol: 452, Pages: 133-145, ISSN: 0012-821X
Johnson BC, Collins GS, Minton DA, et al., 2016, Spherule layers, crater scaling laws, and the population of ancient terrestrial impactors, ICARUS, Vol: 271, Pages: 350-359, ISSN: 0019-1035
Kring DA, Kramer GY, Collins GS, et al., 2016, Peak-ring structure and kinematics from a multi-disciplinary study of the Schrodinger impact basin, NATURE COMMUNICATIONS, Vol: 7, ISSN: 2041-1723
Miljkovic K, Collins GS, Wieczorek MA, et al., 2016, Subsurface morphology and scaling of lunar impact basins, JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS, Vol: 121, Pages: 1695-1712, ISSN: 2169-9097
Monteux J, Collins GS, Tobie G, et al., 2016, Consequences of large impacts on Enceladus' core shape, ICARUS, Vol: 264, Pages: 300-310, ISSN: 0019-1035
Morgan JV, Gulick SPS, Bralower T, et al., 2016, The formation of peak rings in large impact craters, SCIENCE, Vol: 354, Pages: 878-882, ISSN: 0036-8075
Smith RC, Hill J, Collins GS, et al., 2016, Comparing approaches for numerical modelling of tsunami generation by deformable submarine slides, OCEAN MODELLING, Vol: 100, Pages: 125-140, ISSN: 1463-5003
Asphaug E, Collins GS, Jutzi M, 2015, Global Scale Impacts, Asteroids IV, Editors: Michel, DeMeo, Bottke, Publisher: University of Arizona Press, Pages: 661-678, ISBN: 9780816532131
Global scale impacts modify the physical or thermal state of a substantial fraction of a target asteroid. Specific effects include accretion, family formation, reshaping, mixing and layering, shock and frictional heating, fragmentation, material compaction, dilatation, stripping of mantle and crust, and seismic degradation. Deciphering the complicated record of global scale impacts, in asteroids and meteorites, will lead us to understand the original planet-forming process and its resultant populations, and their evolution in time as collisions became faster and fewer. We provide a brief overview of these ideas, and an introduction to models.
Forman LV, Bland PA, Timms NE, et al., 2015, RECOVERING THE PRIMORDIAL IMPACT HISTORY OF CHONDRITES IN UNPRECEDENTED DETAIL USING MASSIVE EBSD DATASETS, 78th Annual Meeting of the Meteoritical-Society, Publisher: WILEY-BLACKWELL, ISSN: 1086-9379
Jacobs CT, Goldin TJ, Collins GS, et al., 2015, An improved quantitative measure of the tendency for volcanic ash plumes to form in water: implications for the deposition of marine ash beds, JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH, Vol: 290, Pages: 114-124, ISSN: 0377-0273
Milbury C, Johnson BC, Melosh HJ, et al., 2015, Preimpact porosity controls the gravity signature of lunar craters, GEOPHYSICAL RESEARCH LETTERS, Vol: 42, Pages: 9711-9716, ISSN: 0094-8276
Miljkovic K, Wieczorek MA, Collins GS, et al., 2015, Excavation of the lunar mantle by basin-forming impact events on the Moon, EARTH AND PLANETARY SCIENCE LETTERS, Vol: 409, Pages: 243-251, ISSN: 0012-821X
Muxworthy AR, Bland PA, Collins G, et al., 2015, MAGNETIC FABRICS IN ALLENDE: IMPLICATIONS FOR MAGNETIC REMANENCE ACQUISITION., 78th Annual Meeting of the Meteoritical-Society, Publisher: WILEY-BLACKWELL, ISSN: 1086-9379
Ormoe J, Melero-Asensio I, Housen KR, et al., 2015, Scaling and reproducibility of craters produced at the Experimental Projectile Impact Chamber (EPIC), Centro de Astrobiologia, Spain, METEORITICS & PLANETARY SCIENCE, Vol: 50, Pages: 2067-2086, ISSN: 1086-9379
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