The Proceedings of the Eighth International Conference on Creationism (2018)

only a subset of the processes in operation during the Flood. One noteworthy process not included pertains to sediment transport and deposition. Currently, sediment transport and deposition via the process of hyperconcentrated flow is missing. In the present treatment sediment falls out of suspension and deposits on the surface whenever the sediment carrying capacity in the turbulent water column is exceeded. It would be straightforward to utilize the bottommost two or three sublayers in the water column to handle the condition of hyperconcentrated flow when it happens to arise. It is anticipated that most of the deposition on the land surface would then occur when a developing hyperconcentrated flow becomes unstable as it switches from laminar to turbulent and dumps its sediment load. This enhancement should increase the realism of the model considerably. Another process not currently included is the dynamic topography arisingfromflowof rock in themantle.Variationsincontinentsurface height from stresses produced by flow of rock in the mantle below can reach several kilometers in amplitude, especially in association with subduction near a continental margin (Baumgardner 1994). Such large amplitude dynamic topography must have affected the water flow and erosion/sedimentation patterns on the continents during the Flood in a major way. In addition, the time dependence of the tectonic processes responsible for the flow inside the mantle also affects the global sea level. Including some approximation of these dynamical processes may well account for the large- scale patterns of transgression and recession responsible for the megasequence structure of the overall sedimentary record. Also missing is a realistic representation of initial topography of the pre-Flood continental surface beyond low topography adjacent to the coasts and higher topography in the continent interior. Recovering more realistic topographical features of Pannotia from clues in the Precambrian rocks will be a challenging endeavor. On the other hand, obtaining dynamic topography from improved mantle dynamics simulations in the future may prove feasible. An additional lack of realism in the current model relates to the locations of subduction zones. In the current model subduction zones were largely static in their locations and generally positioned far from land. Yet in today’s world most subduction occurs adjacent to continents. Likely that was also the case during the Flood. Numerical experiments not described in this paper reveal that the patterns of water flow, erosion, and sedimentation are rather sensitive to subduction zone location. Therefore, in future studies it will be important to include more realism in subduction zone placement and to allow that placement to change dynamically. A crucial aspect of the model that also invites further scrutiny is the locking/slipping mechanics of subducting lithosphere responsible in the model for generating the large-amplitude tsunamis. How this process may have operated during the Flood when plate speeds were so dramatically higher is far from clear. A key issue is the amount of stress the fault between the plates could have sustained without slip occurring. The reduction in rock strength associated with the runaway process in the mantle during the Flood may well have affected the lithospheric lid at the earth’s surface less than it did the mantle. If so, high stress levels in the locked plates combined with weaker rock in the mantle beneath may have worked together to yield large amplitude surface deflections between episodes of slip. Careful numerical exploration of the locking and slip mechanics of the plates in the subduction zone environment is an urgent task to be addressed in the near future. A further deficiency in the current model is the lack of any easily eroded sediment initially present on the continental surface. That lack ought to be simple to alleviate in future studies. Hence, the numerical model described in this paper should therefore be thought of as a work in progress, as a developing framework for addressing the global-scale water flow, erosion, and sedimentation of the Flood. CONCLUSION Numerical simulation offers a means for investigating phenomena that are impossible, either because of their physical scale or the extreme conditions they entail, or both, to explore experimentally in a repeatable manner in the laboratory. The Genesis Flood certainly falls into this category. This paper describes a beginning attempt to apply known physical laws, physical processes that can be investigated in the laboratory, and processes on larger scales that can be studied and characterized by measurements in the present, to model important aspects of this unique cataclysmic event. The numerical model exploits the shallow water approximation to represent water flow in a thin layer on the surface of a rotating sphere corresponding to the earth. It utilizes the theory of open- channel flow to treat the suspension and transport of sediment by turbulent flowing water. As its mechanism for erosion it utilizes cavitation. To drive the water flow it draws upon a currently observable consequence of plate tectonics, namely, the locking and sudden release of the overriding lithospheric plate along its fault contact with a subducting plate in a subduction zone. Today, when the overriding plate unlocks and rebounds, its upward motion can, and often does, generate a water wave known as a tsunami. During the Flood, when plate speeds were orders of magnitude higher than they are today, the amplitudes of the tsunamis were potentially vastly larger. In the numerical model such large-amplitude tsunamis are utilized to drive the global water flow. Along the continental margins water speeds consistently exceed the cavitation threshold, leading to intense erosion there of the continental bedrock. As the tsunamis surge onto the continental surface, the turbulent water transports the eroded sediment inland and deposits it in orderly patterns characterized by large spatial scales. When plate speeds begin to fall due to the exhaustion of gravitational energy driving the flow of rock in the mantle, the tsunamis decrease in frequency and amplitude, water velocities drop toward zero, and the water that had been pulsing across the continental surface drains back into the ocean basin. In the case highlighted in this paper, erosion and deposition rates approach those needed to account for the average sediment thickness on today’s continental surface. This numerical model, basic as it is, sheds new light on several fundamental issues related to the Flood. It seems to account for (1) how such a huge volume of new sediment could arise during the brief time span of the Flood; (2) how the astonishingly thick columns of sediment observed so commonly in continental settings managed to be deposited on top of the normally high-standing continental surface; (3) how the vast lateral scales and horizontal Baumgardner ◀ Large tsunamis and the Flood sediment record ▶ 2018 ICC 304