Researchers now believe they know why Mexican City Cantona disappeared 1,000 years ago.
After studying sediment from a nearby lake where Cantona once stood, researchers at the University of California, Berkeley now believe the city died out due to a high frequency of droughts.
Cantona once stood in a volcanic basin near what is now Mexico City. At the time, it was one of the largest cities in the world, containing about 90,000 people. Although the region was known for its obsidian, the city probably also served as an important trade route and even played a military role from behind its fortified location.
In the modern age, this region of Mexico is most associated with wet summers and monsoons, but that wasn't the case, at least during the period that saw the decline of Cantona. Although there was still rainfall, there wasn't enough to sustain agriculture.
Geographers from the university studied core samples from sediment taken from a lake near where Cantona once stood. These researchers used a combination of chemical composition and carbon-14 dating to determine the age of samples. They then studied the oxygen ratios within those samples to figure out which ones represented a drier time period.
This analysis unveiled that frequent droughts occurred in the area from around 500 A.D. to 1150 A.D. During that time, most of Mexico was dry and did not become wetter again until before 1300 A.D., about the time the Aztec Empire rose to power.
This dry period meant that people began moving away from the city, perhaps in search of wetter climates.
"We can show that both the growth and decline of the site took place during a time period of frequent drought, which forces us to think in more nuanced ways about how political and social factors interact with environmental factors to cause social and cultural change," says Tripti Bhattacharya, a UC Berkeley graduate student. "That makes the study particularly interesting."
This drought possibly affected other cities, as well. Researchers believe that Cantona's population increased at the beginning of its dry period, with many people coming from Teotihuacan, another ancient Mexican city about 100 miles from Cantona because of its own problems with drought. However, eventually, the entire area was affected.
"In a sense the area became important because of the increased frequency of drought," says Roger Byrne, UC Berkeley associate professor of geography. "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."
