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Two new studies in the Journal of Quaternary Science refute the hypothesis that one or more comets/bolides struck North America approximately 12,900 years ago triggering rapid climate change and the start of the Younger Dryas period.
Prior to the Younger Dryas, the climate had gradually warmed from glacial conditions to near modern temperatures, and the massive ice sheets in North America were in full retreat; however, approximately 12,900 years ago, temperatures rapidly plummeted and returned to glacial conditions for about a 1200 year long period. Also about this time, the mammoths and mastodons became extinct in North America.
The two papers challenge two lines of evidence reported and used by others to support the impact theory. One is the report of elevated concentrations of nanometer-sized diamonds in sediments deposited at the onset of the Younger Dryas. It is claimed that these diamonds were formed during an impact. The other is the interpretation that paleofire evidence at a key archaeological site demonstrates massive wildfires at the beginning of the Younger Dryas. It is claimed that the impact caused wildfires that spanned the continent.
(Score: 1, Interesting) by Anonymous Coward on Wednesday January 04 2017, @06:41AM
The first paragraph:
If somehow you still don’t get it, the previous hypothesis was that the Younger Dryas period [wikipedia.org] (a significant period of global cooling that began 12,900 years ago and lasted for approximately a thousand years), was caused by comets or asteroids striking the planet at the time. They have shown that such an impact likely did not cause the Younger Dryas.
(Score: 2) by VLM on Wednesday January 04 2017, @02:40PM
They have shown that such an impact likely did not cause the Younger Dryas.
Well, more precisely they thought they found separate evidence that an impact happened in two specific individual samples. Then some other dudes re-analyzed the samples and were like LOL no fire ash its just "coprolites" (fossilized poop) and the other abstract says no nano-diamonds formed by shock found after all.
With only access to the abstracts all we got is two pairs of he-said she-said and no way to judge which is correct. It would be really messed up if one is right and one is wrong... like if there were massive fires but no nanodiamonds that implies volanoes or just a big ass forest fire? Or the other way around it implies a meteor strike but is just dust without a fire enough to kill mammoths? I guess so, if it kills their plant food.
Neither abstract explains the cause of the Younger Dryas just excludes two samples as being proof, assuming the new papers are correct of course, which they may or may not be.
If both new papers are correct either more data needs to be gathered to find new samples, or you need a new climate theory or something to explain the climate era, because meteors and stuff seemed a really good explanation.
(Score: 0) by Anonymous Coward on Wednesday January 04 2017, @04:27PM
> all we got is two pairs of he-said she-said and no way to judge which is correct
Huh? That *IS* what counts for news in the USA.