Discussion of the hypothesis that the Carolina Bays were created by the saturation bombardment of pieces of ice ejected by an extraterrestrial impact on a glacier during the Ice Age and the possibility that several impacts could have triggered the Younger Dryas cooling event.
Transcript:
The Carolina Bays are shallow depressions with raised rims that are found along the East Coast of the United States. This video discusses the hypothesis that the Carolina Bays were created by the saturation bombardment of pieces of ice ejected by an extraterrestrial impact on a glacier during the Ice Age.
The shallow elliptical depressions with raised rims are oriented toward the Great Lakes. In this LiDAR image of North Carolina, we can see that the ground is completely covered with Carolina Bays except where water erosion has washed them away. Some bays in this image measure four kilometers in length.
Meteor Crater in Arizona measures approximately 1.2 kilometers in diameter and has a depth of 170 meters. By comparison, these Carolina Bays located 27 km southeast of Fayetteville, North Carolina are much larger and almost completely flat. The bays are difficult to detect from ground level because the rims are only one or two meters higher than the center of the bays. This is why they were discovered only after the introduction of aerial photography in the 1930s. Meteor Crater was produced by the impact of a nickel-iron meteorite about 50 meters in diameter traveling at 20 km/s. A Carolina Bay of the same size would require the impact of an ice boulder with a diameter of 180 meters traveling at about 3 km/s.
In 1952, William Prouty proposed that the Carolina Bays had been made by impacts of extraterrestrial objects. He estimated that the total number of large and small bays was about half a million. This number is often quoted in the literature. Prouty based his estimate on counts from Bladen County in North Carolina where water erosion spared only the bays that are on elevated ground as shown in the LiDAR image in the center. The color gradient indicates the elevation. Terrain that has not been eroded by water is completely covered by bays as shown on the image on the right. This means that the total number of bays could be in the millions. Similar elliptical features also oriented toward the Great Lakes occur in Nebraska.
The convergence point of the Carolina Bays and Nebraska Rainwater Basins indicates their point of origin. Davias and Gilbride calculated the convergence point at Saginaw Bay, Michigan. The Carolina Bays do not have any evidence of shock metamorphism or meteorite fragments, so they were not formed by extraterrestrial impacts. The bays are more likely the result of secondary impacts by glacier ice boulders ejected by an extraterrestrial impact on the ice sheet that covered Saginaw Bay during the Ice Age. The ice cover prevented the formation of a typical extraterrestrial impact crater in Saginaw Bay.
The Glacier Ice Impact Hypothesis, published in 2017, proposes that the Carolina Bays and the Nebraska Rainwater Basins were made by secondary impacts of glacier ice ejected in ballistic trajectories by a meteorite impact on the Laurentide Ice Sheet 12,900 years ago. The impacts of the ejected ice boulders liquefied unconsolidated ground, and the ice projectiles created inclined conical cavities that were remodeled into shallow elliptical bays by viscous relaxation.
Some opponents of the Glacier Ice Impact Hypothesis have argued that there was no ice in Saginaw Bay 12,900 years ago at the time of the proposed meteorite impact. The coverage of the glaciers during the Ice Age advanced during stadials and retreated during interstadials, but there are several sources that confirm that there was ice in Saginaw Bay at the time of the extraterrestrial impact. If there had been no ice at the point of the extraterrestrial impact, a recognizable crater would already have been found at that location.
Several sources report that the Port Huron Stadial, from 13,300 to 13,000 years before the present, caused the Laurentide Ice Sheet to re-advance to the southern end of Lake Huron. This image from Eschman and Mickelson shows the advance of the glaciers that covered Saginaw Bay and Huron Lake during the Port Huron Stadial.
Prof. Peter Schultz was one of the 25 co-authors of the 2007 paper by Firestone that proposed that an extraterrestrial impact 12,900 years ago contributed to the megafaunal extinctions and the Younger Dryas cooling. Prof. Schultz studies impacts on ice using NASA's Ames Vertical Gun. His high-speed impact experiments show that an impact on an ice sheet ejects many pieces of ice radially in ballistic trajectories, and that a typical impact crater is not formed on the underlying surface.
In one experiment, Prof. Schultz prepared a sandy surface covered with a thin layer of red sand. The initial impact ejects a fast-moving plume of debris and the vaporized projectile. A conical crater starts to form as sand grains are ejected radially in ballistic trajectories. During the crater excavation, the ejecta curtain forms an inverted cone that expands with time until all the sand particles fall to the ground. The result is a bowl-shaped cavity with a raised rim formed by lateral compressive forces and debris from the excavation.
In another experiment, Prof. Schultz placed a sheet of ice on top of a transparent Acrilite block. The transparent target makes it possible to study the mechanics of the impact below the ice sheet. The oblique high-speed impact on the ice sheet immediately vaporizes the projectile and creates a fast-moving vapor plume. The impact fractures the ice and sends chunks of ice of various sizes in ballistic trajectories. Unlike the impact on sand that creates an ejecta curtain with a uniform expanding conical shape, the impact on ice produces irregular ice shards that form a more chaotic ejecta curtain, and the layer of ice prevents the formation of a typical bowl-shaped impact crater.
The Carolina Bays are evidence of the saturation bombardment by pieces of glacier ice that were ejected by an extraterrestrial impact on the Laurentide Ice Sheet. The great surface density of the bays means that there was no place to hide to avoid getting hit by an ice boulder. It is easy to imagine that a horrific hailstorm by large ice chunks with energies of 13 kilotons to 3 megatons could have created the Carolina Bays and killed the megafauna that inhabited North America. The ice bombardment was probably the main cause of the megafaunal extinction 12,900 years ago. The Younger Dryas cooling event that followed the extraterrestrial impact made life harder for the survivors.
The report in 2018 of an impact crater in Greenland under the Hiawatha glacier has increased speculation that this impact may be associated with the onset of the cooling event 12,900 years ago. If the date is confirmed, there will be three impact sites that may have contributed to the extinction of the megafauna, the onset of the Younger Dryas Cooling Event, and the rise in global sea level.
The Greenland crater measures 31 kilometers in diameter. The mineral composition and the size of the crater indicate that the impact was most likely made by an iron meteorite at least one kilometer in diameter. Analysis of the ice layers of the Hiawatha glacier indicates that the impact may have occurred during the Pleistocene, between about 12,000 and 3 million years ago.
The Greenland Crater is too far north and too small to have killed the megafauna in the continental United States, but an extraterrestrial impact at this location could have pushed a mass of cold Arctic air with hurricane force winds toward Siberia causing some animals to freeze suddenly. Siberia is 3000 kilometers from the Greenland Crater and the North Pole is in a direct line between them, so this is a plausible scenario.
Saginaw Bay has not been confirmed as an extraterrestrial impact site by petrographic analysis. The deepest part of Lake Huron is aligned with Saginaw Bay. Thus far, the only evidence linking Saginaw Bay to the Younger Dryas extinction is the convergence of the Nebraska Rainwater Basins and the Carolina Bays at that location and the assumption that secondary impacts of glacier ice would have caused an extinction from the Rocky Mountains to the East Coast of the United States 12,900 years ago.
The Carolina Bays and the Nebraska Rainwater Basins are found within a radius of 1500 kilometers from Saginaw Bay on terrain south of the Laurentide Ice Sheet. Any animals or humans within this circle would have been killed or seriously injured by the ice impacts. The approach of a comet fragment from the southwest over forested land could have caused widespread burning.
The Iturralde Crater in Bolivia has been difficult to study because it is in the middle of the jungle, but it appears to have been formed by an airburst that could have killed South American megafauna.
The Iturralde crater has a diameter of 8 kilometers and a depth of 20 meters. Analysis of soil samples found large quantities of glassy spherules, which supports the hypothesis that the Iturralde crater may have formed during an air burst by a low density extraterrestrial body. Estimates of the age of the Iturralde Crater range between 11,000 and 30,000 years, which makes it a candidate for the extinction 12,900 years ago.
Clearly, more research is needed to replace speculation with facts. It is now well established that the extinction 12,900 years ago was not caused by the onset of the cold weather event or by the mass killing of megafauna by stone-age humans. The evidence of shocked quartz found at the Greenland crater site serves to reject the arguments that the odds of a comet impact on the Laurentide Ice Sheet during the late Pleistocene are infinitesimal. Even though no physics-based model has been presented to support the Younger Dryas comet impact, the time has come to seriously consider that one or more extraterrestrial impacts caused a global catastrophe when humans already inhabited America. We need to understand how all this happened so that mankind can prepare for the next time.
