Scuba divers from around the world are familiar with the Blue Hole, a stunning geological feature off the coast of Belize. Divers and tourists flock in droves each year to visit the oceanic cave. Another kind of visitor has also taken interest in the formation.

Researchers recently took core samples from drillings around the region and examined sediments collected from within. What they found suggests that a massive drought hit the area right around the same time as the estimates for when the Mayan civilization collapsed. Two new scholarly reports detail the latest efforts to explain what happened to the Mayans, one in the Proceedings of the National Academy of

“When you have major droughts, you start to get famines and unrest,” André Droxler of Rice University, lead investigator of the study, said.

For thousands of years, the Mayan civilization flourished in Mesoamerica, a region which now consists of Mexico and Central America. Mayans developed their own hieroglyphics and mathematics, both of which were advanced for their time period. The Mayans are perhaps best known for the calendar they developed, which mapped out time some ten centuries into the future. The calendar ended in 2012, causing many to anticipate with trepidation the end of the world.

Experts estimate that the Mayan civilization collapsed during the period between 800 and 900 C.E. In 700, the city populations began to decline, and wars became frequent. The city dwellers are thought to have ultimately dispersed, and scattered remnants appeared in the larger surrounding area after rains began falling at normal levels around 1,100 years ago.

By 900 C.E., most of the Mayan cities sat completely empty. Since archaeologists have been unable to find any evidence of a large-scale extinction from war or natural disaster, large-scale drought has become a popular explanation for the mass exodus from the cities. This latest research supports the drought hypothesis.

The research report was published in the Proceedings of the National Academy of Sciences.