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

Following the presentation of that paper at the 2013 ICC, a colleague inquired if I had considered tsunamis produced by catastrophic plate tectonics during the Flood as a possible driving mechanism. Although I had briefly considered this possibility, I had dismissed it because I had thought the tsunami amplitude would be too small. However, prompted by my colleague’s inquiry, I reexamined the idea and realized that, if during the Flood the overriding plate locks witht the subducting plate, even for a few minutes, when the plates unlock and slip, a huge tsunami would result. I further realized that given the total length of the subduction zones that had to be active during the Flood, the total number of such large tsunamis would have been large and their frequency quite high. A simple analysis showed that with plate speeds on the order of 2 m/s, a subduction angle of 45°, and a plate locking interval of 60 minutes, the sea bottom is depressed by more than 5 km. When the plates then unlock and slip, the seafloor rebounds toward its undepressed state, launching a gigantic tsunami easily capable of traversing a supercontinent. Moreover, if even half the length of subduction zones active in the present world were active at any given time during the Flood, that implies some 25,000 km of active zones. If the average segment length where slip occurs in a single event is 1500 km, and if the locking interval is one hour, this implies an event every four minutes. This is equivalent to 15 events per hour, 360 per day, or 54,000 in a span of 150 days. I realized that this represented a potent mechanism for driving high velocity water motion during the Flood deserving careful investigation. Implementing this new feature in the numerical model was not difficult. 2. Large amplitude, high frequency tsunamis yield unexpected consequences As I explored the response of the model with new mechanism for driving water flow, I observed striking new behavior I had not seen previously. I noticed that, as the tsunamis initially surged over the land surface, the water levels not only began to rise but that water levels continued to rise until the continent surface everywhere was deeply flooded. I also observed that the Coriolis effect was strongly influencing the pattern of flow, with strong anti-cyclonic gyres appearing at high latitudes where the Coriolis effect was greatest. The largest water depths were at the centers of these anti-cyclonic gyres. Simple analysis revealed that the Coriolis force associated with the circular water motion was balancing the force from the height gradient of the water piled up beneath the gyre. Emplacement of water onto the continent surface by the tsunami pulses was compensating for runoff from gravity, thereby maintaining the piles of water and the circular pattern of water flow. I realized that this mechanism of repetitive tsunamis provided a rather simple answer to the longstanding puzzle as to how the normally high-standing continents were covered by water for months during the Flood. The answer is that the repetitive large tsunamis were emplacing seawater onto the land surface and thereby compensating for the tendency of runoff due to gravity. Not only did early numerical experiments reveal this tendency for the continental surface to flood quickly and remain flooded as long as the large-amplitude tsunamis continued, it also demonstrated their potency for eroding the continental bedrock, particularly along the continent margins. In addition, the early numerical experiments demonstrated the adequacy of the mechanism for suspending, transporting, and distributing vast quantities of sediment over the continental surface. I subsequently published results from these experiments for two stationary continent configurations (Baumgardner 2016). The first case was a circular supercontinent centered on the equator with a smooth, almost flat surface that covered 38% of the earth, with the remainder of the earth covered with deep ocean. The continent geometry was almost identical to that utilized in Baumgardner (2013). The second case was similar except that the supercontinent shape resembled Pangea. In both cases, the continent surface was quickly flooded by the tsunamis and the flooding persisted as long as the tsunamis were allowed to continue. In addition, relatively stationary anti- cyclonic circulation patterns quickly appeared at high latitudes in both hemispheres from the Coriolis effect. The greatest elevations of the water surface and greatest depths of accumulated sediment were associated with these gyres. As might be expected most of the erosion and sediment generation occurred along the continent margins due to the impinging tsunamis. While these beginning calculations with tsunamis did show promise in being able to account for some of the most crucial aspects of a global Flood as described in Genesis, the sediment patterns in these simple calculations displayed little resemblance to those that blanket the continents today. It was clear that much more realism was needed before the sediment patterns in the model could possibly show even a remote correspondence with the actual record. Therefore, I undertook additional effort to address that need. Much of that effort involved replacing the static continent configuration with a treatment that tracks the breakup of a pre-Flood supercontinent, the reassembly of the resulting blocks into a Pangean supercontinent, the subsequent breakup of that supercontinent and dispersal of its resulting blocks, and their movements to their present locations. I also included a history, based on paleomagnetic observations, of the changing orientation of the earth’s spin axis relative to the continents during the Flood. Tracking the history of the spin axis orientation is important because it controls the spatial expression of the Coriolis effect. Finally, I also added a more realistic topography to the continental surfaces, with a gradual increase in topographic height from -200 m along the coastlines to 1,000 m elevations in the continental deep interiors. 3. Discovery of a numerical artifact responsible for the per- sistent continental flooding As I explored the behavior of this enhanced version of the model, specifically the water flow directions on the continents with the more realistic topography, I noticed a disturbing pattern. I found the water flow was consistently downslope. With a bit of sleuthing I found the cause to be a problem in the numerical formulation. In numerical models that involve fluid flow, accuracy is critical in how fluid is transported from one cell to the next. Because of its inherently small amount of numerical diffusion, I had elected to use what is known as a semi-Lagrangian transport method. Even though the amount of anomalous numerical diffusion is much smaller in this method than in most others, its downside is that it is not perfectly mass-conserving. To guarantee mass conservation, I Baumgardner ◀ Large tsunamis and the Flood sediment record ▶ 2018 ICC 288