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

to visualize and understand. Moreover, it requires dramatically less plate motion and less ocean floor subduction for Pannotia to be transformed into Pangea than do the secular reconstructions. RESULTS We shall now present results from a case with the water motion driven by large-amplitude tsunamis that includes the continent motion history just described. As mentioned in the introduction, these tsunamis are understood to be generated in subduction zones as the overriding plate—after an interval of being locked against a subducting plate—suddenly unlocks, and the two plates rapidly slip past each other. While the two plates are locked together, the sea bottom is dragged downward by the steadily sinking lithospheric slab beneath. When the plates unlock, the sea bottom rapidly rebounds, generating a large-amplitude tsunami. For the case shown in this paper, zones of subduction are chosen to lie along great circle arcs. These zones are divided into sixteen distinct segments, each about 14° of arc in length, which is about 1,500 km. Subduction is assumed to be occurring at an angle of 45° into the mantle along each of these segments with the horizontal speed of the subducting plate assumed to be 1.6 m/s at the beginning of the calculation, increasing to 1.9 m/s at 30 days, and to 2.0 m/s at 70 days. While the subducting and overriding plates are locked, the seafloor in the subduction zone is assumed to be moving vertically downward at a rate of 0.707 times the assumed horizontal plate velocity because of the steady sinking motion of the subducting lithospheric slab beneath. Every two computational time steps, corresponding to an interval 360 s or 6 minutes, one of the 16 segments is allowed to unlock and slip, allowing the bottom of the subduction zone trench to rebound to its nominal, undepressed height. An individual segment therefore slips every 96 minutes. The amplitude of the rebound of the trench bottom is between 6,520 m and 8,140 m (1.6-2.0 m/s x 0.707 x 96 x 60 s). This impulsive uplift of the approximately 14° segment of trench bottom initiates a tsunami that travels across the 4,000-m deep ocean at a speed of about 200 m/s. The generation rate of one tsunami every six minutes is equivalent to 240 per day and 36,000 over a time span of 150 days. Initially the water is assumed to be at rest with its surface at sea level. The continent surface is assumed everywhere to consist of crystalline bedrock. The earth is assumed to be spinning at its current rate of rotation. Understanding the results from the model is a challenge because of the model’s many variable quantities such as water velocity, water depth, erosion rate, cumulative erosion depth, suspended sediment according to particle size for multiple particle size classes, deposited sediment according to particle size, and topographic height accounting for erosion, sedimentation, and isostatic adjustment, just to name a few. Each of these quantities varies both in time and potentially with respect to some 40,000 grid points that span the earth’s surface. The only way a human being can possibly interact with such vast amounts of numerical information is for the information to be represented in a visual manner and then sampled only sparsely in time. Space restrictions in a written paper impose additional limitations. With these considerations in view, I have chosen to include a relatively small set of color plots at a few points in time from the calculation to attempt to afford the reader the opportunity for at least a qualitative grasp of the model results. The times I have selected are at 20, 50, 80, 110, and 140 days from the start of the simulation. Because the continent motion history in this model is similar to that derived from some 70 years of study by the secular geology and geophysics communities, it is possible to connect times in this model with corresponding points in the standard geological time scale. The continent configuration at 20 days corresponds to 470 million years ago in the standard geological time scale (early Ordovician), 50 days to 320 million years ago (early Pennsylvanian/ mid-Carboniferous), 80 days 220 million years ago (late Triassic), 110 days to 160 million years ago (late Jurassic), and 140 days to 40 million years ago (mid-to-late Eocene). Figure 2 provides plots at 20 days for the surface height of either the water or land, whichever is greater; the water depth over the land surface, the cumulative depth of bedrock erosion, the amount of suspended sediment (all particle sizes combined), and the net cumulative depth of deposited sediment. Plots (a) and (b) clearly show water waves in the deep ocean with trough to crest amplitudes of more than 2,000 m. These waves correspond to the tsunamis generated in a repetitive manner, every 96 minutes at a given location, along active subduction zones. Such waves propagate at a speed of 200 m/s in the deep ocean. Plots (c) and (d) of water depth show the extent of the invasion of the tsunami waves onto the land surface. Generally speaking, it is the lower elevation coastal regions that have been flooded at this stage in the simulation. Plots (e) and (f) display the cumulative depth of crystalline bedrock erosion. As might be expected, the most intense erosion is occurring along the continent margins where the tsunami waves encounter the abrupt topographic change from deep ocean to continent. Plots (g) and (h) display the total amount of suspended sediment for all particle sizes, in terms of solid equivalent, in the turbulent water column. Coarse particles tend to settle out of suspension more quickly and nearer to where they have generated by cavitation compared with the finer ones. Plots (i) and (j) show the cumulative amount of sediment deposition of all sediment sizes. Regions of thick deposition generally occur in a band just inland from the coast. It is noteworthy that already at this stage in the simulation these zones in the coastal lowlands display sediment thicknesses of more than 350 m. At 20 days the average depth of bedrock erosion over the entire continent surface is 143 m. The average depth of sediment accumulation is 140 m, and the average amount of sediment in suspension is 3 m, where the averages are over the continental surface area. In all these plots the displacements of Laurentia, Baltica, and Siberia away from the remainder of Pannotia are evident. Figure 3 provides plots at 50 days of water/land surface height, water depth over the land surface, cumulative depth of bedrock erosion, net cumulative depth of deposited sediment. By this stage in the calculation, Baltica and Laurentia have reversed direction and collided with each other, resulting in the Caledonian orogeny. That block has in turn collided with Gondwana, producing the Variscan/ Hercynian/ Appalachian orogeny. Siberia has also collided with Baltica and Laurentia such that Siberia, Baltica, Laurentia, and Gondwana are now all joined together in a manner very similar to Baumgardner ◀ Large tsunamis and the Flood sediment record ▶ 2018 ICC 296