This video discusses the relationship of the Niagara Escarpment and the Michigan Basin with regard to an extraterrestrial impact in the Saginaw Bay region.
Transcript:
The Niagara escarpment. An escarpment is a long, steep slope, especially one at the edge of a plateau or one that separates areas of land at different heights. An escarpment is basically a steep or vertical cliff, either above or below sea level. The Niagara escarpment is notable because it makes a semicircle around the Michigan peninsula.
The escarpment extends eastward south of lake Ontario. The most famous view of the escarpment is at Niagara Falls. The escarpment at Niagara Falls is marked by a drop in elevation between Lake Erie and Lake Ontario of 99 meters or 325 feet. Niagara Falls straddles the border between Canada and the United States. Both countries have hydroelectric generating plants that take advantage of the falling water. The semicircular Niagara escarpment has a center in Michigan close to Saginaw Bay. The Mississippian aquifer is present in Iowa and the Lower Peninsula of Michigan. The aquifer has a circular shape that is concentric with the Niagara escarpment.
The rocky geology of the Michigan peninsula also has the same circular pattern as the aquifer with the youngest strata in the center and older strata forming concentric rings. The Michigan peninsula formed during the Paleozoic era when oscillations of sea level caused many retreats and transgressions of the sea across the Great Lakes region. At times the seas were warm and clear, supporting a myriad of shelled creatures, at other times the seas were muddy, receiving great volumes of fine silts and decayed vegetation from low lying land. Sometimes desert conditions prevailed, and the seas became excessively salty supporting little life, or were brackish with gypsum and sulfide and chloride minerals.
The Paleozoic formations of Michigan all slope from the rim edges to the center of the basin. The Michigan Basin is one of the greatest areas of rock salt accumulation in the world, and these sediments have been the basis of major chemical and plasterboard industries in Michigan. These sediments accumulated during the Silurian period when an extensive blanket of limestone was deposited from New York State to as far as Wisconsin. Within this area of carbonate deposition some localities subsided much more rapidly than others, such as the area that is now lower Michigan and which is the dominant feature developed in the Great Lakes region during the Silurian. Chris Cottrell from Dabbler's Den has a video that discusses geological stratigraphy. He suggests that the impact of a comet fragment on the Laurentide sheet could have formed the depression of the Michigan basin.
The idea of an extraterrestrial impact in the Michigan peninsula is supported by the existence of the Nebraska Rainwater Basins and the Carolina Bays. These are geological features with perfect elliptical geometry whose major axes are oriented toward the Great Lakes region. The bays have a width-to-length ratio of approximately 0.58, which corresponds to cones inclined at about 35 degrees and indicates that the bays originated as inclined conical cavities. A study by Michael Davias of the orientations of the Nebraska Rainwater Basins and the Carolina Bays shows a convergence point in Michigan around Saginaw Bay.
The Glacier Ice Impact Hypothesis, published in 2017, proposes that an extraterrestrial impact on the Laurentide Ice Sheet ejected pieces of ice in ballistic trajectories and that the secondary impacts of the ice pieces created the Carolina Bays and contributed to the extinction of the North American Megafauna approximately 12,900 years ago.
Some scientists have objected to the idea that an impact at Saginaw Bay could have ejected pieces of ice to create the Carolina Bays 12,900 years ago because by that time the Laurentide Ice Sheet had receded. According to this paper by Schaetzl, et al., ice did not occupy the Saginaw Bay region or even any part of the Saginaw Lowlands at the time that this putative impact could have occurred. Thus, such an impact could not have dislodged "ice boulders" that could then have been ejected to great distance to form features such as the Carolina Bays.
Publications like this that say that the Carolina Bays could not have been created by an impact at the proposed time and place could be correct, but they are not useful in explaining the origin of the Carolina Bays.
An explanation is needed for the origin of the Carolina Bays and the Nebraska Rainwater Basins. The elliptical geomorphology, the raised rims and the radial orientation toward the Saginaw Bay region are evidence that these are impact structures. Since these features have a convergence point around Michigan it is reasonable to suppose that an extraterrestrial impact in the Saginaw Bay region during the ice age, when Michigan was covered by the Laurentide Ice Sheet, could have ejected pieces of ice whose impacts created inclined conical cavities that today look like ellipses.
However, if there was no ice in the Saginaw Bay region 12,900 years ago to create the Carolina Bays, the date of the extraterrestrial impact could be wrong, but this is not likely because a platinum anomaly characteristic of an extraterrestrial impact has been reliably dated at 12,900 years ago.
If there was no ice in the Saginaw Bay region, another possibility is that the calculation of the convergence point is wrong. In this case, it will be necessary to calculate a convergence point in a region of the Great Lakes that still had ice 12,900 years ago.
Finally, it is possible that the determination that there was no ice in Saginaw Bay 12,900 years ago is wrong. Glacier coverage is inferred from moraines and evidence of glacial lakes, such as sediments, beach ridges and meltwater outlets. Isn't it possible that an extraterrestrial impact by a meteorite with a diameter of 3 to 4 kilometers could have destroyed the evidence needed to establish the presence of an ice sheet at the point of impact?
We really don't know what happens when a meteorite hits a two-kilometer thick ice layer. A paper by Stickle and Schultz in 2012 tried to explore this problem. These images show one experiment where a pyrex bead is shot at a transparent plasticine target. The first image at 32 microseconds after the impact shows a crater being formed on the surface of the plasticine layer, and almost simultaneously, the bottom of the plasticine layer shows some damage from the shock wave reflection.
Newton's cradle is a device that demonstrates conservation of momentum and energy. The experiment can be used to deduce that when a projectile hits the top of a structural layer, the energy is transmitted to the opposite side of the layer almost immediately. In the case of an impact on an ice sheet, the energy is transferred to the bottom of the layer even as the top of the layer is being destroyed by the impact.
This image shows additional experiments and a numerical model of the impact experiment. Notice the concave shape of the shock wave at the bottom of the target layer. This is analogous to the shape of the Michigan Basin and offers a mechanism to support Chris Cottrell's suggestion that the Michigan Basin could have been created by an extraterrestrial impact on an ice sheet that covered Michigan.
The Niagara escarpment looks like a tantalizing clue about the extraterrestrial impact on the Laurentide Ice Sheet, but appearances can be deceiving. At this time, we don't know whether an extraterrestrial impact on a two-kilometer thick ice sheet could have produced enough compressive force to create the Michigan Basin or to create shocked quartz, which is what will finally convince geologists that an impact did in fact occur.
