Jan Bartek – AncientPages.com – Chemical analysis of a stalagmite from a Mexican cave has provided new insights into the potential causes behind the collapse of the Classic Maya civilization.
Researchers, led by the University of Cambridge, have used oxygen isotope data to reconstruct rainfall patterns between 871 and 1021 CE, coinciding with the Terminal Classic period. This study marks the first time that scientists have been able to isolate rainfall conditions for individual wet and dry seasons during this era.
Credit: Wolfgang Sauber – Public Domain, Mark Brenner. Image compilation – AncientPages.com
The findings suggest that prolonged droughts may have played a significant role in societal decline. Specifically, eight wet-season droughts lasting at least three years each were identified, with one extending for an unprecedented 13 years.
These climatic challenges likely contributed to significant changes within Maya society, including the abandonment of limestone cities in the south and shifts in political power as dynasties came to an end.
This climate data supports existing historical and archaeological records, indicating that construction activities and political engagements at key northern sites like Chichén Itzá ceased during these periods of environmental stress. The precisely dated drought events now offer a refined framework for understanding human-climate interactions during this critical phase in Maya history.
Daniel H. James, David Hodell, Ola Kwiecien, and Sebastian Breitenbach (L-R) at the Maya site of Labna in the Puuc region (Yucatán, Mexico), which was most likely abandoned during the Terminal Classic. Credit: Mark Brenner
“This period in Maya history has been a cause of fascination for centuries,” said lead author Dr Daniel H. James, who conducted the research while a PhD student 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.”
Beginning in the 1990s, researchers started correlating climate records with historical data left by the Maya, such as dates inscribed on significant monuments. This research indicated that a series of droughts during the Terminal Classic period likely contributed to major socio-political disruptions in Maya society.
Daniel H. James installs a drip rate monitor upon a flowstone in Grutas Tzabnah (Yucatán, Mexico) as part of the wider cave monitoring campaign. Credit: Sebastian Breitenbach
Recently, James and his colleagues from the UK, US, and Mexico have utilized chemical signatures found in stalagmites from a cave in northern Yucatán to provide a more precise understanding of these droughts.
Stalagmites are formed when water drips from a cave ceiling and deposits minerals on the floor, creating large formations over time. By dating and analyzing oxygen isotope layers within these stalagmites, researchers have obtained detailed climate information for the Terminal Classic period. Previous studies used oxygen isotopes from lake sediments to assess drought severity; however, lake sediments lack sufficient detail to determine annual climate conditions at specific sites accurately.
“It hasn’t been possible to directly compare the history of individual Maya sites with what we previously knew about the climate record,” said James, who is 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.”
Previous research on stalagmites has successfully determined the annual average rainfall amounts during the Terminal Classic period. However, a team led by Cambridge University has advanced this research by isolating data from individual wet and dry seasons. This breakthrough was made possible due to the relatively thick annual layers, approximately 1mm each, in the stalagmite used for their study. The specific oxygen isotopes present in each layer serve as indicators of drought conditions during the wet season.
“Knowing the annual average rainfall doesn’t tell you as much as knowing what each individual wet season was like,” said James. “Being able to isolate the wet season allows us to accurately track the duration of wet season drought, which is what determines if crops succeed or fail.”
Analysis of the stalagmite data reveals that between 871 and 1021 CE, there were eight wet-season droughts, each lasting a minimum of three years. The most prolonged drought during this period extended for 13 years. Despite the advanced water management techniques employed by the Maya, such an extended drought would have significantly affected their society. Furthermore, the climate data from the stalagmite correlates with dates inscribed on Maya monuments. During times of severe and prolonged droughts, date inscriptions at locations like Chichén Itzá ceased altogether.
Tourists explore the ‘Dome of the Cathedral’, the largest chamber in Grutas Tzabnah (Yucatán, Mexico), and the origin of Tzab06-1. The artificial well ‘La Noria’ now illuminates the cave. Credit: Mark Brenner
“This doesn’t necessarily mean that the Maya abandoned Chichén Itzá during these periods of severe drought, but it’s likely that they had more immediate things to worry about than constructing monuments, such as whether the crops they relied on would succeed or not,” said James.
The researchers say that stalagmites from this and other caves in the region could be vital in putting the puzzle of the Terminal Classic period together.
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“In addition to what stalagmites can tell us about this period in Maya history, they might also be able to tell us about the frequency and severity of tropical storms, for instance,” said James. “As a case study for fine-grained comparisons between climate and historical data, it’s exciting being able to apply methods usually associated with the deeper past to relatively recent history.”
The study was published in the journal Science Advances
Written by Jan Bartek – AncientPages.com Staff Writer