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Old 2nd January 2009, 08:47 AM   #1
macdoc
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Comet strike, Clovis and Climate

This article came up in New Scientist last year - it's an interesting read.

http://www.newscientist.com/article/...html?full=true

Then this one popped in the popular press

Quote:
Gems Point to Comet as Answer to Ancient Riddle


Nanodiamonds, such as these in the black layer of sediment at the Murray Springs archaeological site in Arizona, may explain the extinction of large animals, the disappearance of the Clovis culture and the climate change of an epoch known as the Younger Dryas. (Courtesy Of University Of Oregon)

By Joel Achenbach
Washington Post Staff Writer
Friday, January 2, 2009; Page A02

Something dramatic happened about 12,900 years ago, and the continent of North America was never the same. A thriving culture of Paleo-Americans, known as the Clovis people, vanished seemingly overnight. Gone, too, were most of the largest animals: horses, camels, lions, mammoths, mastodons, saber-toothed cats, ground sloths and giant armadillos.

Scientists have long blamed climate change for the extinctions, for it was 12,900 years ago that the planet's emergence from the Ice Age came to a halt, reverting to glacial conditions for 1,500 years, an epoch known as the Younger Dryas.

In just the last few years, there has arisen a controversial scientific hypothesis to explain this chain of events, and it involves an extraterrestrial calamity: a comet, broken into fragments, turning the sky ablaze, sending a shock wave across the landscape and scorching forests, creatures, people and anything exposed to the heavenly fire.

Now the proponents of this apocalyptic scenario say they have found a new line of evidence: nanodiamonds. They say they have found these tiny structures across North America in sediments from 12,900 years ago, and they argue that the diamonds had to have been formed by a high-temperature, high-pressure event, such as a cometary impact.

"This is a big idea," said Douglas J. Kennett, an archaeologist at the University of Oregon and the lead author of a paper on the Younger Dryas impact hypothesis published today in the journal Science.
continues.....
http://www.washingtonpost.com/wp-dyn...l?hpid=topnews

That has some interesting knock on implications as that is not all that long ago.
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Old 2nd January 2009, 09:01 AM   #2
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We urgently need to develop a minor planet/comet interception and steering capability.
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Old 2nd January 2009, 09:34 AM   #3
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If it's a minor PLANET we need a size large escape pod

Same with a large comet and to a degree even small ones given their speed.

Earth orbit crosser asteroids of a manageable size might be steered - the big ones - well.....one can hope.

Some new info from Tungska has reduced the size of the body that airburst - the problem with that is it then upped the potential frequency of occurrence.

I'm just wondering how this impacts the existing Clovis migration theories - pre and post apocalypse.

One wonders if more cultural and climate shifts are bollide derived.
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Old 2nd January 2009, 09:48 AM   #4
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I think there is good evidence for a Comet strike around that time, but currently the paleo-climate evidence doesn’t seem to support it being the cause of Younger Dryas. The big problem is that a comet impact would have had global effect but the Younger Dryas is mostly or entirely a Northern Hemisphere event.
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Old 2nd January 2009, 10:06 AM   #5
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Originally Posted by lomiller View Post
I think there is good evidence for a Comet strike around that time, but currently the paleo-climate evidence doesn’t seem to support it being the cause of Younger Dryas. The big problem is that a comet impact would have had global effect but the Younger Dryas is mostly or entirely a Northern Hemisphere event.
I don't think the comet impact would necessarily have had global effect; very few winds cross the equatorial belt, which means it's actually very difficult for airborne particles to cross the equator. If we assume conservatively that 90% of the dust kicked up stayed in the Northern hemisphere, then we could easily see a much more significant climate change in the north than in the south.
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Old 2nd January 2009, 10:14 AM   #6
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You can possibly do more about an asteroid than a comet. However its always been a puzzle to me why a comet striking the earth is worse than an asteroid striking the earth? I'm sure its been explained but if I've heard the explanation I've forgotten it.
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Old 2nd January 2009, 12:00 PM   #7
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Comets are usualy worse than asteroids because, in general, comets are larger. You won't hear mention of any 100m comets. Comets are typically only described as being 1 km+ in size.
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Old 2nd January 2009, 12:26 PM   #8
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Originally Posted by drkitten View Post
I don't think the comet impact would necessarily have had global effect; very few winds cross the equatorial belt, which means it's actually very difficult for airborne particles to cross the equator. If we assume conservatively that 90% of the dust kicked up stayed in the Northern hemisphere, then we could easily see a much more significant climate change in the north than in the south.
Even a comparatively small event like the eruption of Mt Pinatubo had a global effect. It’s true that as you move to higher latitudes you need a larger event for it to be felt globally, but to get the effect they are talking about in the Northern Hemisphere would require a very very large event that would most likely have had a global effect.

(Realclimte has an article on the topic here.
http://www.realclimate.org/index.php...r-dry-as-dust/
)
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Old 2nd January 2009, 01:14 PM   #9
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There was a very interesting program on the other day that showed how a comet or asteroid strike into ice would leave no crater.
The actually have a gun that can accelerate a chunk of ice to 13,000 kph in the lab.

It was neat - the fired this material at that speed into a bed of ice and there was no crater.

So indeed it could be pretty localized.

Quote:
comet striking the earth is worse than an asteroid striking the earth? I'm sure its been explained but if I've heard the explanation I've forgotten it.
It's speed mostly - the suckers are really moving.

http://miac.uqac.ca/MIAC/impactearth.htm

Last edited by macdoc; 2nd January 2009 at 01:17 PM.
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Old 2nd January 2009, 07:05 PM   #10
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Originally Posted by Molinaro View Post
Comets are usualy worse than asteroids because, in general, comets are larger. You won't hear mention of any 100m comets. Comets are typically only described as being 1 km+ in size.
You've got that very much wrong. The largest NEA (Near Earth Asteroid) is 1036 Ganymed, at 32 kilometres diameter. There are estimated to be roughly 1000 NEAs over 1km. In contrast, only 82 near earth comets have been discovered in total. Sizewise, even the famous Halleys Comet, which is larger than any NEC, is nowhere near as big as Ganymed, its nucleus being only 20km in diameter.
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Old 2nd January 2009, 10:23 PM   #11
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Was there not some talk previously about a ton of small comets hitting the atmosphere daily - supplying much of the water?
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Old 2nd January 2009, 10:47 PM   #12
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Originally Posted by Damien Evans View Post
You've got that very much wrong. The largest NEA (Near Earth Asteroid) is 1036 Ganymed, at 32 kilometres diameter. There are estimated to be roughly 1000 NEAs over 1km. In contrast, only 82 near earth comets have been discovered in total. Sizewise, even the famous Halleys Comet, which is larger than any NEC, is nowhere near as big as Ganymed, its nucleus being only 20km in diameter.
There are also many smaller cometary bodies. The primary diffence between a comet and an asteroid is that comets tend to have much higher relative velocities, and thus carry much greater potential energy into impact events.
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Old 3rd January 2009, 04:26 AM   #13
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Is it slightly wrong of me to be disappointed that Apophis only has a 1 in 45,000 chance of impacting the Earth in 2036?
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Old 3rd January 2009, 04:36 AM   #14
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Originally Posted by Undesired Walrus View Post
Is it slightly wrong of me to be disappointed that Apophis only has a 1 in 45,000 chance of impacting the Earth in 2036?
I feel the same way, though mainly because if it had turned out differently, if, for instance, we knew that it was on an impact course, we would, I think, very likely attempt to do something about that. And not only do I think we could, but I think it could revitalise the space program.

But for these things (as evidenced in my why we will go to the stars thread) I am something of a dreamer.
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Old 3rd January 2009, 04:40 AM   #15
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Originally Posted by BenBurch View Post
We urgently need to develop a minor planet/comet interception and steering capability.
I agree. Unfortunately, it won't be done until something really catastrophic happens.
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Old 3rd January 2009, 05:26 AM   #16
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Neil Degrasse Tyson said there was a great myth about how to get rid of an asteroid/comet on a collision course with Earth. Blow it up with an explosion, and you then have to deal with many hundreds, if not thousands of chunks of rock slamming into the Earth, causing the same amount of devastation as one large rock.

He said what you need to do is park a small spacecraft in orbit around the rock, gradually changing its original course. Like cancer however, you have to find it early.
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Old 3rd January 2009, 05:31 AM   #17
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Originally Posted by Undesired Walrus View Post
Neil Degrasse Tyson said there was a great myth about how to get rid of an asteroid/comet on a collision course with Earth. Blow it up with an explosion, and you then have to deal with many hundreds, if not thousands of chunks of rock slamming into the Earth, causing the same amount of devastation as one large rock.

He said what you need to do is park a small spacecraft in orbit around the rock, gradually changing its original course. Like cancer however, you have to find it early.
If you managed to blow it up into sufficiently small pieces it could burn up in the atmosphere. Just sayin'.
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Old 3rd January 2009, 07:14 AM   #18
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Quote:
If you managed to blow it up into sufficiently small pieces it could burn up in the atmosphere. Just sayin'.
Mass and kinetic energy do not change under that scenario - only impact crater and there is some evidence that an airburst energy release may be more devastating than a crater event.

Remember all that energy will still go into the atmosphere .
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Old 3rd January 2009, 07:15 AM   #19
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Originally Posted by macdoc View Post
Mass and kinetic energy do not change under that scenario - only impact crater and there is some evidence that an airburst energy release may be more devastating than a crater event.

Remember all that energy will still go into the atmosphere .
Good Point.
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Old 3rd January 2009, 07:21 AM   #20
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You're all thinking along the wrong lines. We need to blow the Earth in two so the asteroid/comet goes between the two halves.
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Old 3rd January 2009, 07:24 AM   #21
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Originally Posted by Starthinker View Post
You're all thinking along the wrong lines. We need to blow the Earth in two so the asteroid/comet goes between the two halves.
DO yo have a jackhammer big enough?
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Old 3rd January 2009, 07:34 AM   #22
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One of the many moments of Armageddon that had me bewildered was the concept of blowing the Asteroid in two. If the damn thing was the size of Texas, why do they only need to drill 800 feet to split it in half?

One of Roger Eberts greatest reviews was of that film:

Quote:
There are several Red Digital Readout scenes, in which bombs tick down to zero. Do bomb designers do that for the convenience of interested onlookers who happen to be standing next to a bomb? There's even a retread of the classic scene where they're trying to disconnect the timer, and they have to decide whether to cut the red wire or the blue wire. The movie has forgotten that *this is not a terrorist bomb,* but a standard-issue U.S. military bomb, being defused by a military guy who is on board specifically because he knows about this bomb. A guy like that, the first thing he should know is, red or blue? ...

Staggering into the silence of the theater lobby after the ordeal was over, I found a big poster that was fresh off the presses with the quotes of junket blurbsters. ``It will obliterate your senses!'' reports David Gillin, who obviously writes autobiographically. ``It will suck the air right out of your lungs!'' vows Diane Kaminsky.

If it does, consider it a mercy killing.
Brilliant.
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Old 3rd January 2009, 07:42 AM   #23
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Originally Posted by Undesired Walrus View Post
One of the many moments of Armageddon that had me bewildered was the concept of blowing the Asteroid in two. If the damn thing was the size of Texas, why do they only need to drill 800 feet to split it in half?
I wonder if all the oil drillers throughout the US mid west throw things at the screen while watching the movie

"Hey Harry look at the idiot, using a type 27/36A rod when everyone knows you use a type 16/211V4"
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Old 3rd January 2009, 09:15 AM   #24
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Is this about when the glyptodons died out? Cause I sure miss them.
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Old 3rd January 2009, 09:35 AM   #25
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Looks like it ....big sucker eh Much meat, comes complete with pot - first slow food movement??



http://en.wikipedia.org/wiki/Glyptodon
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Old 3rd January 2009, 09:43 AM   #26
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Originally Posted by Undesired Walrus View Post
One of the many moments of Armageddon that had me bewildered was the concept of blowing the Asteroid in two. If the damn thing was the size of Texas, why do they only need to drill 800 feet to split it in half?
Actually, that issue isn't necessarily unrealistic or at least without addressment, the drilling wasn't to reach the center of the asteroid, it was to tamp the blast sufficiently so that the force went into the body of the asteroid rather than just being a surface jet.

The problem was in what they were attempting to do, the rationale behind it and the unrealistic results. There might have been realistic ways to address or at least explain these issues, but handwaving and special effects won out over science, ...again.
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Old 3rd January 2009, 09:46 AM   #27
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Originally Posted by macdoc View Post
Looks like it ....big sucker eh Much meat, comes complete with pot - first slow food movement??

http://upload.wikimedia.org/wikipedi...ld_drawing.jpg

http://en.wikipedia.org/wiki/Glyptodon
pot? that thing carries its own kitchen! 3-4 in a row and you've got a village!
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Old 3rd January 2009, 10:01 AM   #28
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Way back when I had money I almost bought a museum replica skeleton for seven grand. I would have had the coolest house in the neighborhood. There is a house here in Mason City with life sized Triceretops in the back yard, a real head turner.
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Old 3rd January 2009, 10:20 AM   #29
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Originally Posted by MG1962 View Post
I wonder if all the oil drillers throughout the US mid west throw things at the screen while watching the movie

"Hey Harry look at the idiot, using a type 27/36A rod when everyone knows you use a type 16/211V4"
No. But they all grinned knowingly at the scene where the crew demand "absolutely NO taxes".


The impact theory is intriguing, but I'd like much more evidence before I abandon the simpler hypothesis. The Clovis hunters were killing off the very megafauna that go extinct suspiciously soon after modern humans reach the Americas. That is probably reason enough to explain the loss of animals which had survived previous (and far harder) ice ages. These creatures were sitting ducks for an intelligent pack hunter- who would have deliberately targeted the younger and smaller animals, creating reproductive stress on the populations. Add that to the worsening climate and you have exactly the sort of eco-catastrophe we have specialised in ever since. With the demise of the big game, a culture based on big game hunting is bound to vanish. One explains the other. There is no mystery.
That scarcely precludes the possible impact of a comet- but what we must bear in mind is that the Younger Dryas (we call it the "Loch Lomond Glacial" in Britain)- marks the end of the most recent glaciation. Maybe they all end this way- with dying pulses of cool / hot climate alternation. Maybe we're in one of the warm pulses now. There may be more short cold spells to come before the next biggie.

We don't really know.

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Old 3rd January 2009, 11:08 AM   #30
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Might be a combination of the two but that widespread layer - as with the Mexico bollide strike is hard to argue with on the physical evidence.


That - nothing before 13k years ago - in terms of humans always puzzled me.

Too distinct.

Maybe the strike opened the path.....if it was as widespread as it appears.

Big pressure wave to carbonize to nano-diamonds across a wide area.
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Old 3rd January 2009, 11:20 AM   #31
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Originally Posted by Undesired Walrus View Post
Is it slightly wrong of me to be disappointed that Apophis only has a 1 in 45,000 chance of impacting the Earth in 2036?
Wouldn't it's projected distance from Earth put it in a path between us and the moon? What is the possibility of it impacting the moon?
We are a somewhat binary planetary system, and the moon is critical to many life forms. Thanks.

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Old 3rd January 2009, 11:32 AM   #32
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Originally Posted by manofthesea View Post
Wouldn't it's projected distance from Earth put it in a path between us and the moon? What is the possibility of it impacting the moon?
We are a somewhat binary planetary system, and the moon is critical to many life forms. Thanks.
Not a expert, but here is some info on Apophis:

http://en.wikipedia.org/wiki/99942_Apophis
Quote:
Additional observations provided improved predictions that eliminated the possibility of an impact on Earth or the Moon in 2029. However, a possibility remained that during the 2029 close encounter with Earth, Apophis would pass through a gravitational keyhole, a precise region in space no more than about 600 meters across, that would set up a future impact on April 13, 2036. This possibility kept the asteroid at Level 1 on the Torino impact hazard scale until August 2006. It broke the record for the highest level on the Torino Scale, being, for only a short time, a level 2, before it was lowered.
And DeGrasse Tyson talking about it:

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Old 3rd January 2009, 09:28 PM   #33
shadron
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Originally Posted by manofthesea View Post
Wouldn't it's projected distance from Earth put it in a path between us and the moon? What is the possibility of it impacting the moon?
We are a somewhat binary planetary system, and the moon is critical to many life forms. Thanks.
The accuracy with which they can plot it precludes it from hitting the moon (though not by very much), just as it does the earth itself. However, if it were to hit the moon, remember that it is 2e10kg, and the moon is 7e22kg, for a ratio of roughly 3e12 (3 trillion in US currency). It would therefore have little effect on the moon, other than creating a really nice show, and probably leaving behind something somewhat smaller than Copernicus craterWP. The energy release is estimated at 800MT TNT equivalent, about 16x bigger than the greatest atomic weapon ever exploded, the Russian Tsar BombaWP
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Old 3rd January 2009, 11:50 PM   #34
Damien Evans
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Originally Posted by Undesired Walrus View Post
Not a expert, but here is some info on Apophis:

http://en.wikipedia.org/wiki/99942_Apophis


And DeGrasse Tyson talking about it:

YouTube Video This video is not hosted by the ISF. The ISF can not be held responsible for the suitability or legality of this material. By clicking the link below you agree to view content from an external website.
I AGREE
well that's not too bad...

I wouldn't want to be on the west coast of America at the time though, but Melbourne shouldn't be affected, supposing it does hit.
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Old 4th January 2009, 05:46 AM   #35
Soapy Sam
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Originally Posted by macdoc View Post
Might be a combination of the two but that widespread layer - as with the Mexico bollide strike is hard to argue with on the physical evidence.
True, but I find myself asking how common such layers are?
If we have a major impact this recently, are similar scale impacts far more common than we think? This is the sort of thing you find because you suspected it might exist and so you looked in the appropriate place. How many other places have we looked?
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Old 4th January 2009, 08:08 AM   #36
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Actually you bring up a good point that smaller bolide impacts do more damage that previously thought

http://www.eurekalert.org/pub_releas...-sso121807.php

But layers distinct enough to show a signature over a wide area - let alone globally ( Mexican - Chicxulub- dinosaurs ) will still be rare in the record.



that rock face covers a huge span of years and there is ONE black layer

The issue with this one under discussion was the apparent lack of a crater ( the Chicxulub site is clear evidence of that massive event but this one has no apparent crater.)

An ice strike /air burst however may offer the answer.

Quote:
The scientists, led by University of Oregon anthropologist Douglas Kennett, say their report offers up a "smoking bullet" - proof it was a comet that set off the sudden, thousand-year freeze and wiped out the big animals of the era.
Working at multiple sites across the continent, researchers found nanodiamonds - microscopic particles thought to be found on comets - in a 13,000-year-old layer of rich sedimentary soil called a "black mat." Beneath the layer with the nanodiamonds, fossils of the animals are abundant. After that layer, they disappear, West said.


"It's extraordinary that tens of millions of animals disappeared synchronously at exactly the time when the diamonds and carbon layer are laid down across the continent," said West, whose co-authors include DePaul University chemist Wendy Wolbach.


Arrowheads and other artifacts from the Clovis culture of humans - an early hunter-gatherer society - also vanish after the black mat was laid down 13,000 years ago.


In 2007, West and a team of scientists published an analysis of black mats from several regions that found heavy metals, soot and charcoal suggestive of meteorite impacts and subsequent fires. The new report says the discovery of nanodiamonds in the same material is more evidence of a cosmic strike.
http://www.physorg.com/news150097682.html

There is some reinforcing info from a well known artifact site analysis - the blog post has some complied into and links

http://remotecentral.blogspot.com/20...dence-for.html

Last edited by macdoc; 4th January 2009 at 08:11 AM.
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Old 23rd July 2015, 10:13 PM   #37
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Adding a bit more to the megafauna story...


Quote:
Mammoths killed by abrupt climate change
July 23, 2015

New research has revealed abrupt warming, that closely resembles the rapid man-made warming occurring today, has repeatedly played a key role in mass extinction events of large animals, the megafauna, in Earth's past.

Using advances in analysing ancient DNA, radiocarbon dating and other geologic records an international team led by researchers from the University of Adelaide and the University of New South Wales (Australia) have revealed that short, rapid warming events, known as interstadials, recorded during the last ice age or Pleistocene (60,000-12,000 years ago) coincided with major extinction events even before the appearance of man.
http://phys.org/news/2015-07-mammoth...t-climate.html
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Old 24th July 2015, 06:03 AM   #38
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Man didn't do it, and it got better all by itself.
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Old 24th July 2015, 12:42 PM   #39
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This time however man whot dun it and it'll get better all by it's lonesome in 3.,000 years or so....mebbe
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Old 24th July 2015, 01:00 PM   #40
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Originally Posted by Damien Evans View Post
If you managed to blow it up into sufficiently small pieces it could burn up in the atmosphere. Just sayin'.

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