At https://phys.org/news/2022-02-tilting-earth-crust-ancient-megafloods.html … the headline caught my attention – tilting the earth's crust governed the flow of ancient megafloods. How does that happen? If the polar ice cap was over NE America and NW Europe during the Late Glacial Maximum, and then, indeed, some kind of tilt must have occurred to get to where the North Pole is situated in the Holocene. However, they aren't talking about anything as dramatic as that, which is no surprise. Pole movement is verboten in mainstream circles. How do they account for the rapid floods that cut out the channeled scablands?
A study in PNAS claims to have identified a crucial factor unrecognised by geologists, even though a good deal of the previous modeling has been done. The changing weight of the ice sheet would have caused the entire landscape to tilt, changing the course of the megafloods. Modeling what happened has been a problem known mostly only to fellow geologists playing around on their computers. Looking at the high water marks to the flooding episodes, and then trying to reconstruct the actual size of the floods, height and depth, are based on estimates that look at modern topography. Well, that is uniformitarianism for you, I suppose. The new study differs, the authors claim, and point towards deformation of the crust by the weight of all that ice locked up in the northern hemisphere, and in particular, in North America. The megafloods, we are told, date between 18,000 and 15,500 years ago. It is worth pointing out to readers that the period, therefore, coincides with the Oldest Dryas event, an unusual period of climate in which temperatures plunged. However, not for 100 per cent of the time. Temperatures seem to have fluctuated, or wobbled, between cool and cold, as if the earth could not decide what mode of rotation it wanted to adopt. On top of this peculiarity the authors have imposed calculations relating to ice gain and ice loss. They may even have it in the back of their minds that the Oldest Dryas episode was too cold to melt all that ice and something else might have been going on – hence the logistics involved in gaining and losing ice mass may have been running as a counterweight to simply warmer weather. It may not have been particularly warm – although it certainly became much warmer at the end of the Oldest Dryas event. One would have thought all the meltwaters were active at that point in time, but it doesn't seem like that was going on as there is archaeological evidence for people active during the Bolling and Alleroed warm periods – where ice formerly existed. Hence, one can see why geologists like to keep these problems to themselves, only occasionally bringing them to the attention of a wider public.
The study confines itself to the channeled scablands and therefore the Cordillera ice sheet along the mountainous zone of western North America. It must have melted fairly quickly as a great body of water is thought to have developed in Montana, known to geologists as Lake Missoula. As the weight of the ice fell it caused the topography to change. Meltwaters continued to fill up Missoula to a breaking point, when the ice dam holding the water back, eventually started to float, allowing megafloods of water to escape and rush down Washington State into the ocean. The study appears to be an ingenious way to keep the idea of multiple floods alive, which was the uniformitarian solution to the Harlen Bretz original single flood. Hence, the study is not about the tilting earth. Not in the least. All they are trying to do is explain how multiple floods could have occurred, a rather ingenious solution it would seem. However, does it really have mileage as we are talking about rapid melt during a very cool period of climate, the Oldest Dryas. The process is said to have occurred over and over again, hence the claim of a floating ice dam – rather than a block of ice that would have been shunted into the scablands along with all that water. Kudos to the authors for thinking outside the box. A clever piece of modeling. One can't help thinking that a real tilt of the earth could have done the job so much more easily. Even in a cool climate period.
You can read the paper itself as well as details on the modeling at https://doi.org/10.1073/pnas.2109502119. .. the Proceedings of the National Academy of Sciences.
There is also another interesting geological story this week – see https://phys.org/news/2022-02-secondary-cratering-earth-wyoming-impact.html … several dozen impact craters have been found in SE Wyoming, in sediment layers of the Permian era. Many of the craters are clustered in groups and aligned along ray like structures. Some craters are elliptical, allowing the incoming path of the impactor to be calculated, and mapped. The trajectories seem to indicate a single source and the surrounding craters were formed by ejected blocks of material thrown up by the impactor as it struck the surface of the earth. Hence the ray like structure.