phenomenon known in earth science circles as true polar wander. With this simpler explanation the 110° of actual continental motion disappears. This was the approach taken in the earlier Baumgardner (2018b) paper and the one we take in this paper as well. Let us consider this topic in a bit more detail. Interpreting significant changes in paleomagnetic latitude as apparent polar wander implies that the magnetic poles remain largely fixed relative to the solid earth while the continents move significant distances across the earth’s surface. By contrast, allowing for a significant amount of true polar wander, where the magnetic poles themselves migrate relative to the solid earth itself, requires dramatically less actual continental motion—over distances that can readily be understood in terms of normal plate tectonics processes. So the issue at hand, especially when one is dealing with measured changes in paleolatitude as large as 110°, is whether the magnetic poles have remained largely fixed relative to the earth’s surface and the continents have actually migrated by vast distances, or whether the continents have moved relatively little and the magnetic poles themselves have moved by large distances. When one considers the brief time span of the Flood, this issue, of course, is accentuated. Indeed, it is difficult to conceive of a means by which the huge Gondwanan continent, which remained intact throughout the entire Paleozoic, might have plowed its way around the earth by more than a quarter of the earth’s circumference in the time span of only a few months. If one chooses the option of true polar wander, the question then arises as to what might have caused such rapid polar wander. The answer almost certainly involves the earth’s rotational characteristics, namely, changes in the relative magnitudes in the earth’s moments of inertia. Such changes could well have been produced by changes in the earth’s internal density distribution, for example, by transit of a significant volume of cold lithosphere from the earth’s surface into the deeper mantle and transit of a comparable volume of hot mantle rock from the core/mantle boundary into the mid and upper mantle. If sufficiently large, such changes indeed are able to alter temporarily the earth’s rotational moments of inertia, leading briefly to a modest amount of rotation of the solid earth about one of its other principal axes. It is helpful here to emphasize that during an episode of true polar wander orientation of the earth’s spin axis in space remains entirely fixed, and the earth’s angular momentum remains perfectly conserved. What happens when one assumes that the large changes in magnetic latitude are the consequence of true polar wander and not apparent polar wander? Investigating this question in his studies leading to his (2018b) paper, Baumgardner made an astonishing discovery. He found that rotating Pannotia 110° clockwise about an axis perpendicular to the plane, when viewed from the east, defined by today’s zero degrees longitude meridian that runs through Greenwich, England, maps the Gondwanan continents in Pannotia, apart from the blocks that formed China, almost perfectly onto those same Gondwanan continents in Pangea! Baumgardner therefore made the bold assumption that, between the onset of the Flood and the point during the Flood when Pangea had assembled, this 110° of true polar wander indeed had occurred. This implied that during the first half of the Flood what today are the continents of Africa, South America, Antarctica, and Australia, plus India and Madagascar had remained stationary on the earth’s surface. They experienced no displacement on the solid earth whatever during the entire Paleozoic part of the record. Moreover, the continents of North America and Europe plus the Siberian portion of Asia, apart from short Paleozoic excursions, also were at the same locations on earth in Pangea as they were in Pannotia at the onset of the Flood. Hence, the continental blocks forming Pangea, apart from the blocks that formed China, were essentially identical in their shapes and locations on the solid earth as they were in Pannotia at the onset of the Flood. We make this very same assumption in the current paper. Pertaining to this issue, a reviewer who views Rodinia as possibly equivalent to Pannotia asked if we might comment on the following claim by Clarey (2020, pp. 159-160): A pre-Flood world that resembled Rodinia would require the consumption of nearly all the pre-Flood ocean crust twice. The first time would be while the continents from Rodinia moved into the configuration of Pangaea, and then a second time when Pangaea split into the present global configuration. Geophysically, the first break-up of Rodinia and reconfiguration into Pangaea would be possible, but it would also consume all of the dense pre-Flood ocean crust. A second move would then be rendered impossible since any significant amount of new ocean crust created while splitting up Rodinia would not have enough energy density contrast to fuel a second episode of subduction. Our response is that assuming some 110° of true polar wander during the early portion of the Flood allows us to begin from a preFlood continent configuration that is essentially identical to Pangea in its location on the earth and its internal constitution (apart from the terranes that eventually form eastern Asia). This effectively eliminates the problem Clarey is describing! Moreover, it allows us to exploit the vast number of paleomagnetic determinations acquired over the past 70 years to obtain what we conclude is a reliable history of the continent motions for the Paleozoic portion of the Flood rock record. We therefore utilize the paleogeographical reconstructions of Blakey and Scotese as our guide for obtaining the relative motions of the continental blocks as a function of time during the earlier portion of the Flood. Since true polar wander affects all these blocks identically, it is legitimate to use reconstructions such as these as a guide for the relative motions. Introduction of true polar wander into the model means that points on the earth’s surface change with time relative to the orientation of the earth’s spin axis in space. To account properly for the Coriolis effect in the numerical formulation that utilizes a computational grid fixed with respect to the solid earth, we need merely to alter the orientation of the spin axis appropriately with respect to the computational grid in the numerics. This requires only a trivial change in the coding to allow the orientation of the spin axis to change with time in a prescribed way. D. Including continent motion history in the numerical model How does one actually incorporate a specific continent motion history into a numerical model? The approach we have taken utilizes an explicit description of the motion of each continent block as a BAUMGARDNER AND NAVARRO Large tsunamis and Flood sediment record 2023 ICC 370
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