View Full Version : New Evidence Links Cosmic Impact to Mass Extinction

2012-Jun-14, 03:41 AM
I knew about the Younger Dryas Period towards the end of the last ice age when the climate was temporarily plunged back into the deep freeze, but I had not been aware of any mechanism for this dramatic change in climate. Recently, three papers have been published in PNAS with evidence supporting an impact event that could explain the extinction of the North American megafauna and the disappearance of the Clovis culture. A press release can be found here (http://www.astrobio.net/pressrelease/4822/new-evidence-links-cosmic-impact-to-mass-extinction). And the three papers can be found here (http://www.pnas.org/content/109/13/E738.abstract), here (http://www.pnas.org/content/109/20/7648.abstract) and here (http://www.pnas.org/content/109/19/7208.abstract). The first is open access.

Ara Pacis
2012-Jun-14, 04:52 AM
But the last two links explicitly claim that they do not support the YDB impact hypothesis.

2012-Jun-14, 04:57 AM
But the last two links explicitly claim that they do not support the YDB impact hypothesis.

My bad -> link before reading :doh:

Well at least they say it's a controversial subject.

2012-Jun-14, 06:32 AM
My understanding, purely from memory, is of an impact to the ice sheet in modern day Quebec about 12,900 years ago. I say this while I live within 5 miles of the province.

Ivan Viehoff
2012-Jun-15, 09:51 AM
Some poor quality studies have been published on the Younger Dryas impact hypothesis. http://en.wikipedia.org/wiki/Younger_Dryas_impact_hypothesis

This has tended to brand the hypothesis as sensationalist nonsense. In turn, this means that work on the hypothesis will be shunned by most reputable scientists. If there is any mileage in it, it will take some convincing evidence presented in studies of exemplary quality to overturn this negative evaluation.

Catastrophism is popular and gets a lot of publicity for your department. Some studies pointed to alleged major tsunami deposits on the coasts of Madagascar and W Australia, and a large round depression in the Indian ocean,to get a good story proposing a large and fairly recent impact. More reputable scientists have been able to show that the alleged tsunami deposits are aeolian (ie wind deposits). In the absence of direct study, made diffciult by its location int he deep ocean, the origin of the large round depression remains unclear.

Ara Pacis
2012-Jun-16, 08:21 AM
You mean Burckle Crater (http://en.wikipedia.org/wiki/Burckle_crater)?

2012-Jun-18, 11:48 PM
For those who haven't seen previous discussion on this topic you need to remember that even if they can prove an impact at the right time (which they have not IMO) this doesn't prove it caused the Younger Dryas cooling.

If there was an impact large enough to cause the Younger Dryas it would have had a cooling effect on both hemispheres, but the best current evidence shows there was no real change in the Southern Hemisphere at the time. In fact some place in the SH continued to warm. At this point it looks like the Younger Dryas was isolated to the Northern Hemisphere, which doesn't fit the profile of warming caused by an impact.