600-year drought responsible for abandonment of ancient city

Chuck Bednar for redOrbit.com – Your Universe Online

Once a thriving metropolis, the city of Cantona was abandoned by its 90,000 residents due to a drought that lasted more than six centuries, according to a new study led by researchers from the University of California, Berkeley and published in the journal PNAS.

Cantona was located just east of modern-day Mexico City in the state of Puebla, Mexico. At its peak, it was said to be one of the largest cities in the New World, and was a major source of obsidian. The city was also likely an important trade route and a key military hub.

However, Cantona was deserted by its citizens during a 150-year span from 900 and 1050 AD. Researchers have long debated why this happened—though many suspected climate change as a factor.

In order to investigate the matter, the UC Berkeley-led team collected sediment cores from Aljojuca, a lake located approximately 20 miles south of the former city. They analyzed those samples and discovered evidence of a 650-year period of frequent droughts between 500 AD and 1150 AD.

Oxygen isotopes

According to reports published by Discovery News, the researchers examined the relationship between oxygen isotopes in the water, which allowed insight into the cycle of precipitation and evaporation. The ratio of these elemental variants was high which, when combined with other sediment analyses, indicates that the area had drier summers

“Overall, Cantona still had wet summers and dry winters, but its regular monsoon season was disturbed by frequent long-term droughts, which likely harmed the area’s crops and water supply, the researchers said,” the website said. “Moreover, the droughts lasted hundreds of years.”

“The decline of Cantona occurred during this dry interval, and we conclude that climate change probably played a role, at least towards the end of the city’s existence,” added lead author Tripti Bhattacharya, a graduate student in the UC Berkeley Departments of Geography and Earth and Planetary Science.

“In a sense the area became important because of the increased frequency of drought,” explained Roger Byrne, an associate professor of geography at UC Berkeley. “But when the droughts continued on such a scale, the subsistence base for the whole area changed and people just had to leave. The city was abandoned.”

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