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Earth Science

What Caused a 1300-Year Deep Freeze? 258

sciencehabit (1205606) writes "Things were looking up for Earth about 12,800 years ago. The last Ice Age was coming to an end, mammoths and other large mammals romped around North America, and humans were beginning to settle down and cultivate wild plants. Then, suddenly, the planet plunged into a deep freeze, returning to near-glacial temperatures for more than a millennium before getting warm again. The mammoths disappeared at about the same time, as did a major Native American culture that thrived on hunting them. A persistent band of researchers has blamed this apparent disaster on the impact of a comet or asteroid, but a new study concludes that the real explanation for the chill, at least, may lie strictly with Earth-bound events."
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What Caused a 1300-Year Deep Freeze?

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  • by Layzej ( 1976930 ) on Monday May 12, 2014 @08:10PM (#46985397)
    "The prevailing theory is that the Younger Dryas was caused by significant reduction or shutdown of the North Atlantic "Conveyor", which circulates warm tropical waters northward, in response to a sudden influx of fresh water from Lake Agassiz and deglaciation in North America. Geological evidence for such an event is thus far lacking. The global climate would then have become locked into the new state until freezing removed the fresh water "lid" from the north Atlantic Ocean. An alternative theory suggests instead that the jet stream shifted northward in response to the changing topographic forcing of the melting North American ice sheet, bringing more rain to the North Atlantic which freshened the ocean surface enough to slow the thermohaline circulation. There is also some evidence that a solar flare may have been responsible for the megafaunal extinction, though it cannot explain the apparent variability in the extinction across all continents." - http://en.wikipedia.org/wiki/Y... [wikipedia.org]
  • Waste of time (Score:5, Informative)

    by scribble73 ( 879745 ) on Monday May 12, 2014 @08:19PM (#46985449)
    This headline promises a lot, but delivers nothing. The article just looks briefly at the controversy -- in other words, we still don't know.

    This comes from a good Journal, but reading it was a waste of time.
  • If Al Gore-like shamans lived back then, the insufficient fervor of the rival shamans in keeping the fires going all day and night would've been blamed for the freeze.

    Anybody failing to keep their fire going would be shamed and punished — unless they paid tribute (to buy global freezing offset credits) to the right shaman, of course.

  • Not really much here (Score:5, Informative)

    by x181 ( 2677887 ) on Monday May 12, 2014 @08:43PM (#46985605)
    Old Argument (Younger Dryas): We found iridium (rare on earth but abundant in meteorites), nanodiamonds and magnetic particles covering ancient tools and mammoth remains at sites which we believe are around 12,000 years old. Therefore, we believe a cosmic collision caused the 1,300 year deep-freeze.

    New Argument: We performed radiocarbon dating on tools found at the 29 sites described in the Old Argument and found that only 3 of the 29 sites were around 12,000 years old. The tools at other sites were much older or younger. Therefore, the deep-freeze was probably not caused by a cosmic collision.
    • Does anyone find it weird that they looked and found 26/29 just happened to be dated incorrectly? I'm assuming that different groups dated the sites originally (depending on who excavated them), and then this group comes in and discovers that they're almost all mis-dated in ways that support their hypothesis. That strikes me as amazingly convenient.
    • if only you were the first post, we could have avoided a hundred others and a lot of useless debate!

      go quicker next time

  • Because I said so.
  • We had to black out the sky to cut off their access to solar energy. We eventually won and abandoned modern technology, but effects of the blackout on the climate could not be overcome.

  • I've written worse, granted. But the whole article seemed to be dismissing the impact cause, and declaring other causes were not evaluated and seeming to postulate a new understanding. And then, in the end, it really seemed to simply be an article questioning the carbon dating, and pointing to sedimentary record as a preferred method of dating and demonstrating an impact wiped everything out.


Nondeterminism means never having to say you are wrong.