Younger Dryas Impact Hypothesis

Kacmarek

Member
The YDIH seems to be a highly polarizing topic in which there are 2 competing theories for significant globalmcooling and megafaunal extinction (as well as the disappearance of the Clovis culture in N America) approx 12,800 years ago.

Younger Dryas Impact Hypothesis : a disintegrating comet or asteroid apprpx 4 miles in diameter broke up in the armosphere over N America, Europe, W Asia leading to enormous temperatures and wildfires. Evidence for this has been found in many locations worldwide including prevalence of shocked quartz, platinum spherules etc

https://martinsweatman.blogspot.com/2022/10/wikipedias-bias-younger-dryas-impact.html?m=1

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The YDIH posits that fragments of a large (more than 4 kilometers in diameter), disintegrating asteroid or comet struck North America, South America, Europe, and western Asia around 12,850 years ago, coinciding with the beginning of the Younger Dryas cooling event. Multiple meteor air bursts and/or impacts are claimed to have produced the Younger Dryas (YD) boundary layer (YDB), depositing peak concentrations of platinum, high-temperature spherules, meltglass, and nanodiamonds, forming an isochronous datum at more than 50 sites across about 50 million km2 of Earth's surface. Some scientists have proposed that this event triggered extensive biomass burning, a brief impact winter and the Younger Dryas abrupt climate change, contributed to extinctions of late Pleistocene megafauna, and resulted in the end of the Clovis culture.[4][5]
There are several issues associated with the validation of the hypothesis :

- Several groups have not been able to replicate the results, leading to papers which claim to comprehensively refute the hypothesis once and for all :

External Quote:

Comprehensive refutation of the Younger Dryas Impact Hypothesis (YDIH)​

  • July 2023
  • Earth-Science Reviews 247(4):104502
  • July 2023
  • 247(4):104502
In addition, individuals lije Graham Hancock have utilised this (prima facie serious scentific hypothesis) to make various extraordinary claims about ancient advanced civilizations

There is a Cometary Research Group (CRG), whose members are seen to be proponents of the hypothesis. Opponents try to portray them as opportunistic and unscientific

Prima facie, careful examination of evidence should lead us to the scientifically rigorous result. But since the publication of the original paper by Firestone et al in 2007 in the Proceedings of the National Academy of Sciences, no less

https://www.pnas.org/doi/10.1073/pnas.0706977104

External Quote:

Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling​

R. B. Firestone rbfirestone@lbl.gov, A. West, J. P. Kennett, +22, and W. S. WolbachAuthors Info & Affiliations
October 9, 2007
104 (41) 16016-16021
The list of proponents and opponents has continued to grow

Seems to be a genuine scientific controversy
 
From watching some of rebuttal videos on Hancock's recent tv show I got the impression that some scientists aren't necessarily against the idea, the thing about Hancock's claim is that you can have an impact without it wiping out his Atlantis supermen.
 
From Wikipedia, the competing hypothesis:
External Quote:
It is an alternative to the long-standing and widely accepted explanation that it was caused by a significant reduction in, or shutdown of the North Atlantic Conveyor due to a sudden influx of freshwater from Lake Agassiz and deglaciation in North America.
The draining of large lakes due to melting of the ice dams that created them is a well-accepted cyclic phenomenon as the temperature rose and fell. Glacial lake Missoula drained west a number of times to create the "channeled scablands" of Washington State, while huge glacial Lake Agassiz drained the other direction, and caused sea levels to rise to the extent that it is believed to be the cause of the submerging of Doggerland on the other side of the Atlantic, and thus the separation of Britain from continental Europe.

But the Storrega slide, an undersea subsidence off Norway that caused a large tsunami, is also believed to have played a part in the destruction of Doggerland. There is no reason why a comet could not have similarly played a part in the Younger Dryas period. It would be naïve to think that a geological event must have one and only one cause. I understand why various researchers might vigorously defend their own pet hypotheses, but major events are rarely that simple.
 
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Seems there is recent further study which has found some corroborating evidence in favour of the hypothesis :

https://phys.org/news/2024-06-reveals-comet-airburst-evidence-years.html#google_vignette

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Now, UC Santa Barbara emeritus professor James Kennett and colleagues report the presence of proxies associated with the cosmic airburst distributed over several separate sites in the eastern United States (New Jersey, Maryland and South Carolina), materials indicative of the force and temperature involved in such an event, including platinum, microspherules, meltglass and shock-fractured quartz. The study appears in the journal Airbursts and Cratering.

"What we've found is that the pressures and temperatures were not characteristic of major crater-forming impacts but were consistent with so-called 'touchdown' airbursts that don't form much in the way of craters," Kennett said.
Journal article citation :
External Quote:
More information: Christopher R. Moore et al, Platinum, shock-fractured quartz, microspherules, and meltglass widely distributed in Eastern USA at the Younger Dryas onset (12.8 ka), Airbursts and Cratering Impacts (2024). DOI: 10.14293/ACI.2024.0003
Lets see how the opponents of the YDIH respond to this .... given that they had published (in 2023) a research which purportedly, once and for all, comprehensively refuted the hypothesis

External Quote:

Comprehensive refutation of the Younger Dryas Impact Hypothesis (YDIH)​

Authors Vance T. Holliday a, Tyrone L. Daulton b, Patrick J. Bartlein c, Mark B. Boslough d, Ryan P. Breslawski e, Abigail E. Fisher e, Ian A. Jorgeson e, Andrew C. Scott f, Christian Koeberl g, Jennifer R. Marlon h, Jeffrey Severinghaus i, Michail I. Petaev j, Philippe Claeys
Edited to add :
It appears that the journal "Airbursts and Cratering " is a new journal set up by the CRG group itself (one of the key proponents of the YDIH)
Hence the rigour of peer review/evidence assessment etc is to be seen .....
 
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Edited to add :
It appears that the journal "Airbursts and Cratering " is a new journal set up by the CRG group itself (one of the key proponents of the YDIH)
Hence the rigour of peer review/evidence assessment etc is to be seen .....
If you have to create a new journal to get your results published, that is generally not a good sign. Even crackpots like Randell Mills can find (sometimes even non-predatory) journals to publish in.

But as the refuting review points out, a bigger problem is the ever-changing postulates of their hypothesis. They have for some reason decided that there must have been a Younger Dryas Impact event, vehemently defends their bad, unreplicable results and conclusions (like insisting on fungal sclerotia is really evidence of an impact event followed by wildfires or that the megafauna extinction was swift) and whenever the "evidence" they put forward is too thoroughly refuted, as with the original supernova and Donnelly's comet hypotheses, they move on to the next thing instead. They don't share data, they were caught manipulating images for the Sodom paper and they have been proven wrong or simply misinterpreted things that were outside their actual area of expertise too many times for me to give them the benefit of doubt.

To me, this is not a true scientific controversy. It's a small clique of people against the larger consensus, much as with climate denialism or the COVID lab leak theory (though I must admit that the YDIH is more likely than either of those, in my opinion. They could find irrefutable evidence of a large impact event that had some influence on the climate during that period, even though it seems unlikely and the chances for it being big enough to explain all or most of it are slim to none, I'd wager).
 
Evidence for this has been found in many locations worldwide including prevalence of shocked quartz, platinum spherules etc

Metallic spherules are a bit like graphene was- thought to be rare and formed in extraordinary events, turns out they're pretty much all over the place (and can be made at home by Mick West without using exotic gear IIRC).

As Skalman says, the megafauna extinction wasn't swift, and it seems to have occurred on different continents at different times.

External Quote:
Major extinctions occurred in Australia-New Guinea (Sahul) beginning approximately 50,000 years ago and in the Americas about 13,000 years ago, coinciding in time with the early human migrations into these regions. Extinctions in northern Eurasia were staggered over tens of thousands of years between 50,000 and 10,000 years ago, while extinctions in the Americas were virtually simultaneous, spanning only 3000 years at most. Overall, during the Late Pleistocene about 65% of all megafaunal species worldwide became extinct, rising to 72% in North America, 83% in South America and 88% in Australia, with all mammals over 1,000 kilograms (2,200 lb) becoming extinct in Australia and the Americas, and around 80% globally.
Wikipedia, https://en.wikipedia.org/wiki/Late_Pleistocene_extinctions

Even hypothesising a long-term comet or family of comets/ asteroids making return visits until being ejected from the solar system, or being gobbled up by the Sun or Jupiter, it's not credible that they repeatedly graze Earth without a direct impact and that they hit a different continent each time. (Admittedly I'm simplifying a bit, the Pleistocene extinctions do have temporal / location overlaps).

Shocked quartz was first identified following nuclear tests, and Eugene Shoemaker (of undisputed cometary impact fame) found it in large (terrestrial) meteorite impact craters. There is a layer at the Cretaceous-Paleogene boundary (what used to be called the Cretaceous-Tertiary boundary).
So far, so dramatic; but just like those pesky spherules with less than exotic origins,

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Lightning also generates planar deformation features in quartz and is capable of propagating appropriate pressure/temperature gradients in rocks and sediments alike. This very common mechanism may significantly contribute to the accumulation of shocked quartz in the geologic record.
https://en.wikipedia.org/wiki/Shocked_quartz
 
It appears that the journal "Airbursts and Cratering " is a new journal set up by the CRG group itself (one of the key proponents of the YDIH)
Hence the rigour of peer review/evidence assessment etc is to be seen .....

As @Skalman noted above, creating your own journal to publish your own theory is a red flag. Sound a lot like the journal DeNovo, created expressly and solely to publish dubious DNA results confirming Bigfoot.

One of the problems with a new journal, is many may just ignore it and their claims. This gives people like Hancock ammo to claim these ideas are being sequestered and not taken seriously. Same claim he made when a paper claiming the mountain Gunung Padang was actually a pyramid was recalled due to lack of evidence.

People like Hancock need the YDIH because he sees it as a catastrophic event that wiped out all evidence, or at least the easy to find evidence, of his Atlantean culture. The sudden global impact of the comet/asteroid caused his proposed Atlanteans to flee wherever it was they lived, destroying their cities AND causing them to fan out and spread a catastrophically neutered version of their culture to the "savages" less educated folks that didn't live in Atlantis. Thus, the less educated Clovis culture suddenly disappeared with the Younger Dryas, or did it (bold by me):

External Quote:

The end of the Clovis culture may have been driven by the decline of the megafauna that the Clovis hunted, as well as decreasing mobility resulting in local differentiation of lithic and cultural traditions across North America.[15] Beginning around 12,750-12,600 years Before Present, the Clovis culture was succeeded by more regional cultures,[16] including the Folsom tradition in central North America, the Cumberland point in mid/southern North America,[17] the Suwannee and Simpson points in the southeast,[18]and Gainey points in the northeast-Great Lakes region.[19] The Clovis and Folsom traditions may have overlapped, perhaps for around 80-400 years.[20] The end of the Clovis culture is generally thought be the result of normal cultural change through time.[15].

There is no evidence that the disappearance of the Clovis culture was the result of the onset of the Younger Dryas, or that there was a population decline of Paleoindians following the end of the Clovis culture.[69]
https://en.wikipedia.org/wiki/Clovis_culture

I wonder how many of the CRG group align with Hancock?
 
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