There are now a lot of web sites to visit on the decline of the Hopewell culture, which was based in the valley of the Ohio River. It fell into decline roughly 1600 years ago. However, before proceeding, we may note this general date also witnessed the decline of various other cultures and high societies around the world, from the Gupta dynasty of India, the contemporary Chinese state, as well as the decline of the Roman and Persian empires. The latter led to the eventual invasion and conquest of Islamic armies in both Persia, the Levant, and North Africa. Hence, looking at the bigger, global, picture, Hopewell was not alone in its decline, and the possible arrival of new tribes from the west. What is unique with Hopewell is that we now may have one of the reasons for that decline. Similar evidence for a similar set of events in the Old World has not been determined. But then, nobody has been looking for that evidence.
Hopewell was at its peak between 200BC and AD 300. One could say the same thing about Rome. After that, it was all downhill. The Hopewell people are thought to be the ancestors of the Algonkian tribes, and the HJaudensaunee [better known as the Iroquois]. Hopewell is best known for its symmetrical earth mounds which they left behind for newcomers to wonder and look at with a certain amount of awe. These are regarded as both ceremonial, and astronomical, we are told at www.space.com/comet-impact-decline-hopewell-people-ohio … Archaeologists, in addition, have found evidence of artifacts made of materials coming from sources from a widespread region of North America, from Canada to the Gulf, and from the Rockies to the Atlantic. It was a period of material plenty, coinciding with similar in China, India, western Asia and Europe. It also coincided with the Roman Warm Period, roughly 200BC- AD300 – which is exactly the time period assigned to the peak of Hopewell.
Native American anthropologist Kenneth Tankersley, and his team, analyised sediments near eleven Hopewell archaeological sites, and found micrometeorites, tiny fragments shed by a passing comet. It is alleged. One might also relate it to a Chelyabinsk type meteor airburst, exploding fairly high in the atmosphere. The origin of the meteor is another matter. That could have been shed by a passing comet, but one suspects this is simply a scenario that is possible rather than irrefutable. Perhaps more than one meteor exploded and shattered, distributing bits of it over a fairly wide area. Whatever, it is imperative to read the actual article yourself before coming to an opinion – see www.nature.com/articles/s41598-022-05758-y …
According to Tankersley, the micrometeorites are rich in platinum and iridium, two elements known from impact craters. They go on to say it was probably an airburst event and did not penetrate far enough into the atmosphere to leave a crater behind. At Milford Earthworks, just outside modern Cincinnati, there is what looks like a comet shaped earthwork going back to Hopewell. The article and some of the links have a sketch of the site taken from the Smithsonian. It could represent either a comet or a meteor, as visible from the surface of the earth. Tankersley also claims there were widespread landscape fires by the evidence of charcoal in sediments. The authors claim to have a desire to inform people how such events affected historical communities. See also www.sci-news.com/archaeology/hopewell-comet-10515.html … which makes the point that the comet or meteor link follows on the toes of the Younger Dryas boundary event, two Argentinian ones, in roughly 6000 and 3000 years ago, and the Tall el-Hammam meteor of 3700 years ago. This suggests, according to the sci news writer, that such natural catastrophes were far more common than previously suspected. One might add, previously 'allowed.' The link continues to speak in terms of comets as recorded by the Chinese, as well as encounters with Comet Halley with the inner solar system. It seems the Hopewell people collected the meteor fragments and made jewelry and musical instruments, such as pan flutes, from them.
At www.sciencedaily.com/releases/2022/02/220201143951.htm …. we have, instead, a rapid decline of the Hopewell culture, 1500 years ago, which might be explained by falling debris from a near earth comet. Going to the actual Nature article – see link above or go to https://cosmictusk.com/hopewell-comet-airbursts-in-ohio-and-midwest/ … where George Howard appears to accept the idea of airburst which do not necessarily require comets in the vicinity. The concentration of microspherules suggests the explosion laid town debris in a NE to SW direction – which is similar to the orientation of the comet lookalike earth figure at Milford Earthworks. Platinum, iridium, and microspherules also occur in low concentrations well to the south, at Indian Fort Mountain in Kentucky. This is in a north to south direction which they have to explain as possibly the result of local weather factors such as winds that tend to flow from west to east, deflecting the low concentration away from the south west. Hence, the low concentration debris may have fallen to the ground after the initial blast [produced by the explosion].