Comet Cooling Nano-diamonds? What caused the Younger Dryas?
Did a comet explode in the sky 13,000 years ago? Did it leave reflective nano-diamonds in the sky and cause the earth to cool resulting in The Younger Dryas?
As I sipped my coffee this morning, I read a The Chicago Tribune report on a comet cooling climate theory. The article was spawned by a recent paper which was evidently published in Science on Friday. (Why don’t newspapers link? GRRR!)
As I like to keep up with various theories related to climate change, I read the article with interest. ,The Chicago Tribune reported:
The authors, led by University of Oregon anthropologist Douglas Kennett, theorize that the comet exploded above the Earth’s surface, raining fragments upon North America and starting fires across the continent. That would have ushered in an abrupt global cooling and caused the “megafauna” extinction.
Evidently, the authors have not convinced everyone. Archeologist Daniel Amick, an associate professor of anthropology at Loyola University Chicago is quotes saying:
“When most archeologists heard about it they were somewhat dismissive,” Amick said. “We would think, ‘How in the world could we have missed this? How could this spectacular kind of event have occurred and never even dawned on us?’ “
Naturally, as I’m on vacation, I felt compelled to rush to the computer and google to learn more about this theory. I found this article in Scientific America, which provides a bit more background, and actually names the climate period triggered by the comet: The Younger Dryas. Scientific America also linked to the article discussing specific evidence for the comet explosion. The Washington Post also has a nice article.
Wikipedia’s article on The Younger Dryas mentions the comet theory, calling it The Younger Dryas Impact Event. This theory was discussed as early as 2007. Evidently, according to proponents of the comet theory, the comet is thought to have exploded over the Great Lakes setting off fires in various locations in the North America.
The story is also being discussed at physics forums. You can find discussions of evidence for and against various theories there. Lack of crater ranks is a difficulty for this theory. (BTW: I found the physics forum because I remember watching some television program where a scientist suggested some previous cooling period was caused by the eruption of volcanos, and which mentioned the eruption of the Lake Toba super-volcano. You’ll find some discussions of volcanism and climate change there.)
If the comet theory gains ascendancy, what will it displace? According to Wikipedia:
The prevailing theory holds that the Younger Dryas was caused by a significant reduction or shutdown of the North Atlantic thermohaline circulation in response to a sudden influx of fresh water from Lake Agassiz and deglaciation in North America.
That said, this might not be an either/or issue. The Washington Post report reveals the comet theory includes the Lake Agassiz draining theory.
The impact scenario incorporates the meltwater scenario. The scientists say that the impact could have destabilized and melted the edges of the ice sheet resting on the northern tier of the continent.
What have I learned from all this? There are a variety of theories for the cause of The Younger Dryas. The comet theory is spectacular. The Lake Agassiz theory is the prevailing theory. It’s also rather spectacular — what with the quite sudden draining of a huge lake into Hudson Bay.
I predict we will read more about this in the upcoming year and for that matter, the upcoming decade. More specifically, I predict a television documentary with scientists showing us the dark streaks in sediment layers and images woolly mammoths and saber tooth tigers dieing as North American forests burn.
Written by lucia.Comments Closed: If you would like them re-opened, Contact Lucia
Comments
Mike N (Comment#7957) January 2nd, 2009 at 12:40 pm
“More specifically, I predict a television documentary with scientists showing us the dark streaks in sediment layers and images woolly mammoths and saber tooth tigers dieing as North American forests burn.”
I can see it now, Michio Kaku, “A com-et is like a snowcone. But if you drop that snowcone on the ground, it gets realllly dir-ty. A com-et is like a dirty snowcone” Thanks for that bit of enlightenment, Dr. Kaku!
(note: I don’t really mean to slight the guy, he’s cool and he’s got great hair,
but sometimes his analogies are a bit goofy)
lucia (Comment#7958) January 2nd, 2009 at 1:04 pm
I like tv science documentaries. That said, they are sometime sort of cartoon like!
Mike C (Comment#7978) January 2nd, 2009 at 5:45 pm
I always wondered why no Younger Dryas type events occured at the begining of other interglaciations. If the comet caused the Lake Agassiz drainage (which in turn shut down the N Atlantic Current) then everything comes together because there is plenty of evidence for both.
Where I disagree is that the kind of fires that would have occured would have lasted for less than a season, the atmosphere would have cleansed itself in a short amount of time. You would need an Agassiz type of an event (resulting in a shut down of the N Atlantic Current) for the Younger Dryas to last as long as it did.
Bill Jamison (Comment#7979) January 2nd, 2009 at 6:27 pm
I saw the story about this but it never occured to me that the nano-diamonds in the atmosphere reflected sunlight and caused the cooling. I assumed the theory was that the impact caused fires and a huge amount of dust to be thrown into the atmosphere. I thought the nano-diamonds were just a way of proving the probability of an impact.
lucia (Comment#7981) January 2nd, 2009 at 6:51 pm
Bill–
You may be right. Maybe the diamonds are just evidence of the comet.
MikeC– I agree that the aerosol theories seem unlikely to explain something as long as the Younger Dryas. I’m waiting for the made for tv documentary!
Mike C (Comment#7983) January 2nd, 2009 at 7:44 pm
Lucia, You need to watch Discovery more often… they had something on this at least 9 or so months ago. The evidence for an impact is very compelling.
lucia (Comment#7985) January 2nd, 2009 at 8:26 pm
MikeC–
Can I take credit for a hindcast?
Mike C (Comment#7987) January 2nd, 2009 at 8:46 pm
errrrr… maybe it was national geo
http://www.youtube.com/watch?v.....mp;index=7
DeWitt Payne (Comment#7992) January 3rd, 2009 at 8:32 am
What happened to a Dansgaard-Oeschger event as being the most likely cause of Younger Dryas? Of course we don’t really know what causes D-O events either, but they happen too often and too regularly to be related to comets.
Mike C (Comment#8007) January 3rd, 2009 at 1:39 pm
Here is part 1 of a 6 part you tube series by Dr West.
http://www.youtube.com/watch?v.....mp;index=1
EW (Comment#8011) January 3rd, 2009 at 2:23 pm
Beatles have summarized it best: Lucia in the sky with diamonds!
Steve McIntyre (Comment#8166) January 6th, 2009 at 4:17 pm
The current view of geologists seems to be that, ontra Broecker, the Lake Agassiz outburst was via the Mackenzie River into the Arctic some time after the YD event and not into the Atlantic as a cause – see
http://www.eeescience.utoledo......_EOS05.pdf .
In various articles, Wunsch has argued convincingly against Broecker’s shutdown cartoon.
Mike C (Comment#8286) January 8th, 2009 at 12:28 am
RC’s post on the matter excludes any mention of evolutionary bottle necks, mass extinctions, black mat, iridium clovis people and etc. Anyone care to guess why?
tty (Comment#8434) January 9th, 2009 at 4:06 pm
The main problem as I see it is that if YD (Younger Dryas) was caused by an impact you would expect it to start abruptly and then trail off. It didn’t it ended if anything even more abruptly than it started.
Also YD lasted some 800 years, it is hard to see how the climatic effect of an impact could last that long.
Another problem is that while YD is unusually large, similar cold snaps (called Dansgaard-Oeschger events) occurred periodically during the last glaciation. Were they all caused by impacts?
As for the melting caused by a cometary impact it wouldn’t be that large. I calculated the energy released by an impactor consisting of frozen methane arriving at 30 kms-1. Making very optimistic assumptions about energy transfer to the ice it would take a 40 cubic kilometer impactor to melt enough ice to fill Lake Superior. Such a large impactor would go right through the ice and leave a large crater.
lucia (Comment#8435) January 9th, 2009 at 4:11 pm
tty– I don’t think the papers suggest the melting happened as a result the heat of impact being transferred to the ice. I think the argument is more indirect. Maybe ice cracked and water flowed, out; maybe local fires, etc.
That said, I don’t know details. Mostly, I thought this was interesting when I read the article.
But, from what I read, it seems the theory about the other worldly object at least arriving in the atmosphere looks pretty strong, but not everyone is convinced it caused the beginning of the YD. (This is my impression anyway.)
Mike C (Comment#8436) January 9th, 2009 at 4:35 pm
tty, The YD was caused by a massive dumping of fresh water and ice bergs into the N. Atlantic, shutting down the conveyor. The shut down would have happened in a matter of days. What it would have taken to resume the conveyor is beyond me, but once the warm water started flowing again, I am sure the warmth would have returned quickly.
Dansgaard-Oeschger events are rapid warming followed by slow cooling. YD was a rapid cooling. And as you stated, the two different events are of a significantly different magnitude.
Also, the Laurentide Ice Sheet was already melting. The existence of Lake Agassiz is well documented. You may remember the Levy / Schumaker comet that struck Jupiter. It was fragmented, the authors of the articles discussed here think the comet that struck was also fragmented. What is different about asteroids and comets is that comets usually explode in the atmosphere as was the case with Siberia in 1908. That impact didn’t leave a crater, just 80 million trees blown down. The main thrust, though, is the sudden, massive dumping of fresh water and ice bergs into the Arctic and North Atlantic.
Nevertheless, you still need to explain the black mat, nano diamonds, iridium, mass extinctions and evolutionary bottlenecks and etc.
bobskinner (Comment#8444) January 9th, 2009 at 8:25 pm
NatGEO broadcast a program in 2007 entitled “Mammoth Mystery” (available as item #X95095 at National Geographic’s online store) covering many aspects of this issue.
Dennis Cox, Fresno, Ca. (Comment#9407) January 25th, 2009 at 6:40 pm
I am only a layman with a high school education but I may have the location of the blast structure from the YD event.
http://theholocenecomet.spaces.live.com
Take a look
Curtis Thompson (Comment#10837) March 1st, 2009 at 3:36 pm
I have found a faint crater around 18 miles in diameter centered approximately at Five Lakes, Michigan using satellite images from this web site.
http://topex.ucsd.edu/WWW_html/srtm30_plus.html
This is close to the Gainey, Michigan Clovis site.