Posted on 01/11/2006 1:33:43 PM PST by blam
Dry Spell Linked to Demise of the MayanKonrad A. Hughen, a geochemist at the Woods Hole Oceanographic Institution, said sediments from the Cariaco Basin in northern Venezuela clearly record a long dry siege that struck the entire Caribbean starting in about the seventh century and lasting more than 100 years. Within this dry period, said Hughen, there were years of virtually no rainfall. It was in those periods of extra dryness, he said, that the Mayan civilization went through a series of collapses before its final demise... The civilization collapsed and many of the sites were abandoned early in the 800s. They were later reoccupied only to collapse again, with some cities deserted in 860 and others in 910... A severe dry spell in 910, he said, "was the last straw."
by Paul Recer
Thu Mar 13, 2003 5:27 PM ETMaya Civilization Done In By Brightening Of The SunThe researchers found the drought episodes occurred during the most intense part of the sun's cycle. Not only that, the researchers found the droughts occurred at times when archeological evidence reflects downturns in the Maya culture, including the 900 A.D. collapse. Such evidence includes abandonment of cities or slowing of building and carving activity. Archaeologists know the Maya were capable of precisely measuring the movements of the sun, moon and planets, including Venus. Hodell said he is unaware, however, of any evidence the Maya knew about the bicentenary cycle that ultimately may have played a role in their downfall.Drought caused by solar cycle may have doomed the MayansA cyclical brightening of the sun appears to have triggered a severe 150-year drought that brought down the civilization of some of the ancient world's most accomplished astronomers, the Mayans, according to a study published today.
by Lee Bowman
Writing in the journal Science, researchers at the University of Florida and the Lawrence Livermore Laboratory in California report that evidence from lake sediments indicates the Yucatan Peninsula, center of the Mayan empire, undergoes a drought every 208 years.
This interval is almost identical to a known 206-year cycle in the sun's intensity, said David Hodell, professor of geology at the university and lead author of the study.
"Looking at this series of sediment cores, it looks like changes in the sun's energy output are having a direct effect on the climate of the Yucatan and causing the recurrence of drought, which is in turn influencing the Maya evolution," Hodell said.
Hodell and colleagues had suggested in a 1995 study that the ninth-century collapse of the classic Mayan civilization came in the midst of a period that was the driest in more than 1,000 years.
They based the conclusion on analysis of a sediment core from Lake Chichancanab, on the north-central Yucatan Peninsula in Mexico. Sediments deposited layer by layer give scientists a time line of changes in climate, vegetation and land use.
In a return trip to the lake last year, the researchers collected a new series of core samples and noted layers of gypsum concentrated at certain levels in the cores. The lake's water is nearly saturated with the mineral, but during dry periods more water evaporates and the gypsum builds up at the bottom of the lake, giving a marker for ancient droughts.
Although they vary in depth, and thus the intensity of the drought they represent, the deposits occur almost exactly every 208 years. The researchers found that this cycle closely matched a previously documented solar cycle that's tracked by measuring certain radioactive substances in the soil. These tend to peak during the most intense part of a 206-year cycle of solar activity.
During those periods, the energy received by Earth from the sun increases by less than one-tenth of 1 percent, Hodell noted. But the additional energy could have been enough to change any of several circulation patterns that affect tropical weather generally and rainfall over the Yucatan specifically, the researchers said.
Climate scientists remain uncertain how much effect the long-term solar cycles have on global temperatures. Most doubt the sun has more than a minor influence on the global warming trend that's been going on for several decades, but some contend the influence is still poorly understood and may turn out to be significant.
"The Maya were highly dependent on rainfall and surface reservoirs as their principal water supply," the researchers said, so dry spells lasting decades and even centuries would have had a particularly "detrimental impact on Maya food production and culture."
The scientists found evidence not only for arid events in the ninth century, but also for several other long droughts before and after that period. Archaeological evidence suggests social upheaval resulting from each of the droughts.Sun key to Mayan misery?The ancient Mayans may have had good reason for their fascination with the heavens, new research by climate historians suggests.
by BBC News Online's Ivan Noble
Friday, 18 May, 2001, 12:09 GMT 13:09 UK"It's hard for me to believe that's just a coincidence." -- David Hodell University of FloridaIt seems that the Mayan homeland in central America was plagued by droughts which appear to have followed a cycle determined by the Sun.
Researchers at the University of Florida, US, analysed sediments from a lake on the Yucatan Peninsula in Mexico and found a pattern of drought repeating every 208 years.
The pattern matches a cycle of brightening and dimming in the Sun.Sediment sample"It looks like changes in the Sun's energy output are having a direct effect on the climate of the Yucatan and causing the recurrence of drought, which is in turn influencing the Maya evolution," said David Hodell, lead author of the study.
In 1993, Professor Hodell and his colleagues extracted a sediment sample from Lake Chichancanab in northern Yucatan documenting 9,000 years of climate history.
They found that the driest period of the current era was from AD 800 to 1000, coinciding with the collapse of the classic Mayan civilisation in the 9th Century.
This time they went back to the lake and found data that backed up their findings and pointed to other periods of drought coinciding with other declines in Mayan building activity.
They found evidence for major dry periods between 475 and 250 BC, and AD 125 and 210, which, they believe, coincides with the abandonment of pre-classic Mayan sites in the Mayan Lowlands.Tree ringsThe evidence is by no means conclusive, but, as Professor Hodell explained to the journal Science: "It's hard for me to believe that's just a coincidence.
"I think drought did play an important role, but I'm sure there were other factors, such as increasing population, degradation of the land, and socio-political change, that interacted.
"Civilisation collapse has got to be complex," he said.
Archaeologists specialising in Mayan history have described the climate evidence as compelling, but agree with Professor Hodell that it is not sufficient by itself to explain the Mayan collapse.
But other climate researchers using tree ring dating (dendrochronology) have also found evidence of a bicentennial drought cycle in step with the variation of the Sun.
The research appears in the journal Science.
If you'd like to read a good book explaining how tree rings have been used to unravel historical mysteries, try "Exodus to Arthur". Great read.
I'm just wondering how tree rings can tell us about the number of people who died during an epidemic.
I don't believe anyone is claiming they can do a population count by looking at tree rings. They look at the tree rings to determine the severity of an incident and can say, 'this must have had some effect on the population.'
They're population has made one Helluva comeback!
This was clearly the result of the Europeans refusing to allow the natives to continue human sacrifices. The gods became angry.
Sounds like bubonic plague, the pneumonic form. Some people think Black Death was actually Ebola virus because it was seen in areas not heavily infested by rats. Some people Ebola is responsible for plagues.
Most interesting.
Yup. I saw a one hour program on the Black Death and one scientist said that at least two killing 'agents' were going on then.
I have read that Black Death was likely caused by more than one diseases, ranging from bubonic plague, anthrax, and possibly Ebola.
I find this story very interesting because we've always been taught that the 'New World' was an Eden full of happy harmonious people that the white man destroyed when he brought over horrible diseases and greed for natural resources. We're all supposed to have a national culture of guilt and shame over this.
The scientific community probably won't give these researchers the time of day. If they did research to "prove" that the white man was even more horrible and destructive than previously thought, they'd give them Nobel prizes.
Self ping.
Looks very interesting!
They didn't have cows. They had an extreme shortage of protein. That's why they had so many human sacrifices, they ate the bodies afterward.
self ping
So, what's the explanation as to the amoeba and bacteria in Mexico's so-called 'potable water'? These illustrious, "concerned" scientists might want to consider the overall detrimental effects of that...like high-to-extremely rampant cases of Hepatitis A, B, C, typhus, and overall depression of population's immune system due to gruesome health conditions (makes for easy transmission of tuberculosis).
All those doctors, so little change.
To oversimplify: by studying tree-rings.
Yes, but it still can be caused locally. Introduced, so to speak, "intra locally." The agent can be remaining latently in the environment (my hunch) and then being released after proliferating by certain environmental conditions.
If there's a long period of latentcy by whatever the agent is, then, in effect, yes, there is then a "virgin population" present when the agent is brought forth. But, the agent may just very well always be present in the local enviroment, and the second agent of change is environmental within that environment, thus exposing the by-that-time "virgin population" in that same location to the infectious agent.
Because populations lose immunity over time. And, sometimes there's no immunity at all to certain infectious agents, particularly those causeing hemorraghic fevers.
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