Stalagmites in Mexican caves reveal period and severity of drought through the Maya collapse

“This period in Maya history has been a cause of fascination for centuries,” mentioned lead writer Dr Daniel H. James, who carried out the analysis whereas a PhD scholar at Cambridge’s Department of Earth Sciences. “There have been multiple theories as to what caused the collapse, such as changing trade routes, war or severe drought, based on the archaeological evidence the Maya left behind. But in the past few decades, we’ve started to learn quite a lot about what happened to the Maya and why, by combining the archaeological data with quantifiable climate evidence.”

Starting within the Nineteen Nineties, researchers started to piece collectively local weather information with these left by the Maya, such because the dates they recorded on key monuments, to indicate {that a} sequence of droughts through the Terminal Classic was a probable contributor to the large socio-political upheaval in Maya society.

Now, James and his co-authors from the UK, US and Mexico have used the chemical fingerprints contained in stalagmites from a cave within the northern Yucatán to convey these droughts into a lot sharper focus.

Stalagmites kind when water drips from the ceiling of a cave, and the minerals contained within the water develop into massive deposits on the cave flooring. By courting and analysing the layers of oxygen isotopes inside the stalagmite, the researchers extracted extremely detailed details about the local weather within the Terminal Classic interval. Earlier analysis has measured the oxygen isotopes contained in lake sediment to find out the severity of drought, however lake sediment doesn’t comprise sufficient element to pinpoint local weather situations in any given 12 months at a specific web site.

“It hasn’t been possible to directly compare the history of individual Maya sites with what we previously knew about the climate record,” mentioned James, who’s now a postdoctoral researcher at University College London (UCL). “Lake sediment is great when you want to look at the big picture, but stalagmites allow us to access the fine-grained detail that we’ve been missing.”

Earlier analysis on stalagmites has decided annual common rainfall quantities through the Terminal Classic, however the Cambridge-led crew have now been in a position to go additional, and isolate data from particular person moist and dry seasons, because of comparatively thick (about 1mm) annual layers within the stalagmite used on this examine. The particular oxygen isotopes in every layer are a proxy for wet-season drought.