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  1. #1
    Mid
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    Tree rings reveal two droughts that sealed the fate of Angkor

    Tree rings reveal two droughts that sealed the fate of Angkor



    Today, the city of Angkor in Cambodia lies in ruins. But a thousand years ago, life there was very different. Then, Angkor was the heart of the Khmer empire and the largest preindustrial city of its day. It had a population of a million and an area that rivalled modern Los Angeles. And the key to this vast urban sprawl was water.

    Radar images of the city by the Greater Angkor Project (GAP) revealed that Angkor was carefully designed to collect, store and distribute water. The “Hydraulic City” included miles of canals and dikes, irrigation channels for supplying crops, overflow channels to cope with a monsoon, massive storage areas (the largest of which was 16km2 in area), and even a river diverted into a reservoir. Water was the city’s most precious resource, allowing it to thrive in the most unlikely of locations – the middle of a tropical forest.

    But water, or rather a lack of it, may have been part of Angkor’s downfall. Brendan Buckley from Columbia University has reconstructed the climate of Angkor over the last 750 years, encompassing the final centuries of the Khmer Empire. The records show that Angkor was hit by two ferocious droughts in the mid-14th and early-15th century, each lasting for a few decades. Without a reliable source of water, the Hydraulic City’s aquatic network dried up. It may have been the coup de grace for a civilisation that was already in severe decline.

    Many theories have been put forward for the downfall of Angkor, from war with the Siamese to erosion of the state religion. All of these ideas have proved difficult to back up, despite a century of research. Partly, that’s because the area hasn’t yielded much in the way of historical texts after the 13th century. But texts aren’t the only way of studying Angkor’s history. Buckley’s reconstruction relies on a very different but more telling source of information – Fujian cypress trees.



    The trees in question grow in Bidoup Nui Ba National Park in neighbouring Vietnam. They’re a while away from Angkor in Cambodia but their location is far less important than their age. These trees have been growing for around a thousand years and they were around when Angkor was in its prime.

    Throughout this time, the climate affected their speed of growth. During years of plenty, they expanded in width far more quickly than during unfavourable drought years. These trends are reflected in the size of their rings and Buckley sampled those by cutting cylindrical cores from the trees. These samples could be very accurately carbon-dated and they provide an invaluable record of the climate in Southeast Asia over at least the past 759 years.

    In Buckley’s record, two droughts stood out in terms of their severity and length. The first one in the mid-1300s was the most sustained period of drought in the region over the last eight centuries. The second, while shorter, was often more severe, and included the driest year on record – 1403. The timings of these droughts coincided with periods when the surface temperature of the Pacific Ocean was unusually high. Buckley suggests that El Nino, a periodic warming of the Pacific, may have driven the two dry spells.

    These disasters have been corroborated by other evidence. Records from Chao Phraya in Thailand also referenced severe droughts in the 14th century, and the dry spells may even have extended into Sri Lanka, India and China.

    During this time, the climate also reversed dramatically, with intense monsoons following the two droughts. These oscillating extremes of too little water following by far too much of it pounded the infrastructure of the Hydraulic City. Today’s ruins show signs of the failing structures that marked the city’s end days. Assaulted by sediment carried in floods, some canals suffered metres of erosion in a short space of time. One, which linked the capital with a nearby lake, is now filled with coarse sand and gravel, which suggests that it was rapidly filled by a single flood. That would have suddenly cut the city off from a major water source.

    There are signs that the people of Angkor tried to cope with their fluctuating environment by modifying their network. However, that’s easier said than done with a criss-crossing infrastructure that spans a thousand square kilometres. The complicated lattice of waterways would have struggled to adapt.

    Of course, a changing environment was far from the only reason behind the fall of Angkor. By the time the droughts kicked in, the city was already weakened by social, economic and political strife. Buckley simply thinks that the climate simply sealed the city’s demise. In fact, others have suggested that some force may have pushed the local people to move from inland agriculture to maritime trade. Buckley says that this transition coincides neatly with the aftermath of the first drought.

    Reference: Buckley, B., Anchukaitis, K., Penny, D., Fletcher, R., Cook, E., Sano, M., Nam, L., Wichienkeeo, A., Minh, T., & Hong, T. (2010). Climate as a contributing factor in the demise of Angkor, Cambodia Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0910827107

    Images: Angkor Wat by Bjørn Christian Tørrissen;
    tree by Juan Pablo Moreiras

    blogs.discovermagazine.com

  2. #2
    loob lor geezer
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    Thanks for sharing.

  3. #3
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    Interesting. What a marvolous site the Angkor is.

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    Quote Originally Posted by Mid View Post
    Tree rings reveal two droughts that sealed the fate of Angkor



    In Buckley’s record, two droughts stood out in terms of their severity and length. The first one in the mid-1300s was the most sustained period of drought in the region over the last eight centuries. The second, while shorter, was often more severe, and included the driest year on record – 1403. The timings of these droughts coincided with periods when the surface temperature of the Pacific Ocean was unusually high. Buckley suggests that El Nino, a periodic warming of the Pacific, may have driven the two dry spells.

    There ya go, Global warming, I mean 'climate change' was the cause. Too much industrial pollution, too many gasoline engines I tell ya. We're doomed. Repent, repent, ban all cars, it's the only way.

  5. #5
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    Quote Originally Posted by palexxxx
    There ya go, Global warming, I mean 'climate change' was the cause. Too much industrial pollution, too many gasoline engines I tell ya. We're doomed. Repent, repent, ban all cars, it's the only way.
    Ignorance is bliss, eh?

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    dunno mate

  7. #7
    Mid
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    Possible new explanation found for sudden demise of Khmer Empire
    Bob Yirka
    January 3, 2012


    Map of Southeast Asia circa 900 CE, showing the Khmer Empire in red, Champa in yellow and Haripunjaya in light Green plus additional surrounding states.
    Image: Wikipedia.

    (PhysOrg.com) -- The Khmer Empire, known to many as the Angkor Civilization, was a society of people that lived for several centuries in Southeast Asia in what is now Cambodia, Thailand, Laos and Viet Nam. What has kept the memory of the empire alive are the huge structures built by the people who lived in the area during that time. Also of note were the roadways, canals and water movement and storage systems that were constructed to support a large population. But like many other lost cultures, what was once a flourishing metropolis, in a very short period of time, gave way to collapse.


    Now, work by a group of scientists indicates it may have been due to drought. The group, led by Mary Beth Day, an earth scientist with the University of Cambridge, is to have the results of their efforts published in a report in the Proceedings of the National Academy of Sciences.

    The Khmer Empire existed from the period between the 9th and 15th centuries and was centered around the city of Angkor. During that time, it’s very clear that great effort was put into capturing massive amounts of water that came from the skies during the monsoon seasons in the summer, to support drinking and crop growing during the rest of the year. The system apparently worked great for a long time, then suddenly didn’t. The reasons put forth for this sudden change have varied, from disease or warfare, to public strife, to changing environmental conditions. Now, it appears due to this latest research, that at least one of the major factors was indeed environmental.

    To find out if the problem was a dearth of water due to changes in the weather or the water system, the team took soil samples from one of the largest reservoirs (called barays) built by the Angkor people. Digging down as far as six feet, the team found that prolonged drought and perhaps overuse of the soil for farming may have led to a society unable to feed itself, a sure and straight path to an untimely demise if ever there was one.

    In studying the soil samples, the team was able to see sediment deposits that had built up on the bottom of the baray over time. During the years leading up to 1431, thinner layers indicted less water became available for storage. They also showed that the rainfall was more erratic. Instead of steady rains during the monsoon seasons, huge storms would erupt flooding farmlands and dumping massive amounts of soil into the baray, which were then followed by periods of no rain at all. The result was much less water available for drinking and growing crops during the drier seasons, and possible destruction of crops that the people were able to grow, due to flooding.

    This new research doesn’t prove for a fact that it was drought that led to the demise of the Khmer Empire, of course, as there were other factors involved. War with neighbors, the conversion of many of the inhabitants to Buddhism, and natural dispersion due to increasing trade with other countries, all likely had a hand. But it does appear that changing weather patterns might have been the final straw.

    physorg.com

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    Quote Originally Posted by Mid View Post



    (PhysOrg.com) -- The Khmer Empire, was a society of people that lived for several centuries in Southeast Asia in what is now Cambodia, Thailand, Laos and Vietnam.
    Well from the looks of that map, a small portion of lower Burma is also included.

  9. #9
    Mid
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    Quote Originally Posted by WujouMao

    Well from the looks of that map, a small portion of lower Burma is also included.
    indeed

  10. #10
    Mid
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    In log coffins, first glimpses of a mysterious Asian people
    Kevin Krajick
    May 9, 2012



    (Phys.org) -- Dendrochronologist Brendan Buckley’s usual occupation is drilling straw-like cores from old trees and extracting information about past climates by studying their rings. To extend the record beyond the time of living trees, he sometimes takes samples from long-dead trees, or even from timbers in ancient buildings. In 2010, the Lamont-Doherty Earth Observatory scientist was part of a team that traveled into the remote Cardamom Mountains of southern Cambodia to investigate human burials contained in coffins carved from entire logs.

    The group, led by Nancy Beaven of New Zealand’s University of Otago Medical School, traveled by boat, motorcycle and finally by foot through the forest to reach cliffs where burials lay. At one site, 20 feet off the forest floor was a ledge protected by an overhang, where lay a row hollowed-out logs, along with ceramic jars. Many held remains. There was a smell of bat guano. Some team members, including Cambodian archeologists, were nervous about offending the spirits of the dead, and before touching anything, they prayed to them to tolerate their intrusion.

    Some of these sites have been known since the 1970s, but little study has been undertaken, and the locations of some have since been lost. To date the sites and study diet and other factors at the site Buckley visited, researchers took smalll samples of bones, soil, plants and other material. Buckley had hoped to extract sliver-width cores from the coffins to study their rings, but the caskets were too crumbly, and he had to settle with a few chunks half the size of a pinky, to be sent for radiocarbon dating. Whether the spirits were offended, no one is sure. But during the 10-day stay, Beaven broke her arm, and Buckley badly injured a shoulder; in the dark of some nights, wild elephants stormed the camp, and had to be driven off by lighting of torches and banging of biscuit tins.

    According to a just-published paper by the team in the journal Radiocarbon, the wood and bone samples date to between 1395 and 1650 AD. This was concurrent with the decline and fall of the great Angkor empire, which ruled much of southeast Asia until around 1432.

    Buddhism was then the main religion of the region, but Buddhists practiced cremation, and these people did not. They seem to have been part of a separate, unidentified ethnic group that possibly lived in isolation, or may have been fleeing from the mainstream urban population who viewed them as savages, said Buckley. “This is our first real glimpse into who these people were,” he said.

    Buckley has previously studied the fall of Angkor itself, by hiking into remote places of southeast Asia to find old trees, but this was his first mortuary expedition. You can hear sounds from the expedition on this Canadian Broadcasting Corp. segment from the Cardamom Mountains.

    phys.org

  11. #11
    Neo
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    Very interesting information. Science comes to the aid of history once more.
    Thanks for sharing Mid.

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