From AD 618 to 907, the Tang dynasty was considered a high point in art, literature and economy through trade with India and the Middle East, but was weakened by revolts and natural causes before the last Tang emperor was eventually overthrown by one of his own military governors.
Evidence of nature's hand in the dynasty's fall came from sedimentary core samples taken from a lake at Zhanjian in coastal southeastern China. Scientists from Geoforschungszentrum in Potsdam, Germany reported that the magnetic properties and titanium content of these samples are probably indicative of a strong winter cycle in the East Asian monsoon cycle. Three times in the last 15,000 years, these particularly strong winter monsoons came during the same periods as markedly weak summer monsoons. The first two such periods came during the last ice age, but the last occurred from 700 to 900.
A history of peasant uprisings contributed to the fall of the dynasty, but the monsoon shifts -- marked by long droughts and weak summer rains -- caused the crop failures that sparked such uprisings.
The scientists compared titanium records from the Huguangyan lake with those from the Cariaco basin in Veneauela, and found interesting parallels. The tropical precipitation shifts noted by the scientists are also thought to have affected the other side of the pacific, having similar detrimental affects on Mayan civilization's classic period, which is believed to have occurred around the same time as the Tang dynasty.
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