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

again for simplicity. I suspect, however, that contributions from other processes by comparison were small. I further assume that the cavitation erosion of crystalline continental bedrock results in a distribution of particle sizes corresponding to 70% fine sand, 20% medium sand, and 10% coarse sand. Here the fine sand fraction also includes the clay and silt, which are assumed to flocculate to form particles that display settling behavior identical to that of fine sand. Mean particle diameters for these three size classes are 0.063 mm, 0.25 mm, and 1 mm, respectively. In this model I neglect carbonates which in the actual rock record represent on the order of 30% of the total sediment volume. I recognize that it is difficult to imagine how feldspar, even when reduced by cavitation to 0.063 mm particle sizes and smaller, might be transformed to clay minerals in the brief time span available during the Flood. I acknowledge that a significant portion of the clay in the shales and mudstones in the Phanerozoic sediment record may well have been derived from shales and mudstones of the pre- Flood earth. For example, the Precambrian tilted strata exposed in the inner gorge of the Grand Canyon, rocks that include the Unkar Group, the Nankoweap Formation, and the Chuar Group, display total thicknesses of about two miles, mostly of shale and limestone (Austin 1994). Even more impressive, the Mesoproterozoic (Precambrian) Belt Supergroup, exposed in western Montana, Idaho, Wyoming, Washington, and British Columbia, is mostly mudstone (shale, fine sand, and carbonate) and up to 8 miles in thickness (Winston and Link 1993). These examples hint that there may have been a vast quantity of mudrocks on the pre-Flood earth, possibly enough to account for most of the clay and carbonate rocks in the Flood sediment record. Exploring the consequences of initial conditions that include a substantial layer of pre-Flood mudstone sediments is an attractive task for future application of this model. Appendix E of Baumgardner (2016) provides a description of the cavitation submodel. It is implemented in the numerical code by means of a single equation involving three adjustable parameters. One of these parameters is the cavitation threshold velocity. For the calculation described in this paper, that threshold velocity is set to 15 m/s, below which no cavitation, and hence no erosion, occurs. Appendix E also describes the criteria for deposition and for erosion of already deposited sediment. Given that the average thickness of Flood sediments on the continents today is about 2,000 m, it is not surprising that a numerical model capable of eroding, transporting, and depositing that much sediment will yield sediment thicknesses in some locations that significantly exceed that average value. In early tests it was found that the calculations become unstable unless some degree of isostatic compensation is allowed in locations where the sediment thicknesses become large. Appendix F in Baumgardner (2016) describes how isostatic compensation is included. Symmetrical compensation is applied for the negative loads that arise from bedrock erosion. To describe the water flow over the earth in a quantitative way, the numerical model makes use of what is known as the shallow water approximation. This approximation requires that the water depth everywhere be small compared with the horizontal scales of interest. The depth of the ocean basins today—and presumably also during the Flood—is about four kilometers. By contrast, the horizontal grid point spacing of the computation grid for the case described in this paper is about 120 km. The expected water depths over the continental regions, where our main interest lies, are yet much smaller than those of the ocean basins. Hence the shallow water approximation is entirely appropriate for this problem. That approximation allows the water flow over the surface of the globe to be described in terms of a single layer of water with laterally varying thickness. What otherwise would be an expensive three- dimensional problem now becomes a much more tractable two- dimensional one. Appendix G in Baumgardner (2016) outlines the mathematical approach for solving the shallow water equations for the water velocity and water height over the surface of the earth as a function of time. These equations express the conservation of mass and the conservation of linear momentum. They are solved in a discrete manner using what is known as a semi-Lagrangian approach on a mesh constructed from the regular icosahedron as shown in Figure 1 of Baumgardner (2016). A separate spherical coordinate system is defined at each grid point in that mesh such that the equator of the coordinate system passes through the grid point and the local longitude and latitude axes are aligned with the global east and north directions. The semi-Lagrangian approach, because of its low levels of numerical diffusion (Staniforth and Cote 1991), is also used for horizontal sediment transport. Seven layers of fixed thickness are used to resolve the sediment concentration in the vertical direction, with thinner layers at the bottom and thicker layers at the top of the column. These same numerical methods have been applied and validated in one of the world’s foremost numerical weather forecast models, a model known as GME developed by the German Weather Service in the late 1990’s (Majewski et al. 2002). The code that incorporates these many numerical features specifically for modeling the hydrological aspects of the Genesis Flood has been named ‘Mabbul’. That word, of course, is the one used exclusively for the Flood in the Hebrew Old Testament. 2. Accounting for continent motion history The previous study (Baumgardner 2016) utilized static continents. The present study has added a displacement history for the various continental blocks spanning, in terms of geological nomenclature, the Paleozoic, Mesozoic, and Cenozoic eras, that is, the portion of the geological record formed during the Flood. While the reconstruction of continent motions since the early Mesozoic has relatively small uncertainty because of the abundance of constraints from the present-day ocean floor, the motions during the Paleozoic typically have much more uncertainty because of the lack of surviving Paleozoic seafloor. The primary observational data for recovering the Paleozoic continent motions are from paleomagnetism. Magnetic minerals in igneous rocks, provided that the rocks have not been significantly reheated since they crystalized, can record the orientation of the earth’s magnetic field when the rocks crystallized. By measuring the magnetic declination and inclination in suitable igneous rocks from many points through the geological record for a given continent, one can construct a paleolatitude history for the continent. This procedure unfortunately provides no information on paleolongitude. Paleomagnetic determinations were first undertaken in the late 1940’s. By the early 1950’s paleomagnetic ‘polar wander paths’ for Europe and North America were being published showing that both continents, relative to today’s North Baumgardner ◀ Large tsunamis and the Flood sediment record ▶ 2018 ICC 291