The cause of the collapse of the Classic Maya civilization is one of the great archaeological mysteries of our time, and has been debated by scholars for nearly a century. Some scientists suggest that a period of intense drought occurred in conjunction with the Classic Maya Collapse and could have contributed to Mayan misfortune.
Scientists have reconstructed climate at the time of the Maya civilization by studying lake sediment cores from the Yucatan Peninsula. It is possible to reconstruct changes in the balance between precipitation and evaporation (P-E), a common indicator of drought, by measuring oxygen isotope data from the shells of gastropods and ostracods (Figure 12). Lake H2O molecules containing the isotope 18O evaporate less easily than H2O molecules with 16O. Thus, during periods of strong evaporation, the lake water becomes enriched in 18O (values of δ18O are high). These isotopic values are incorporated into the growing shells of gastropods and ostracods that live in the lake.
Another proxy for P-E is the % sulfur of the lake sediments. Evaporation concentrates sulfur in the lake water. If the sulfur concentration becomes high enough, salts such as gypsum (CaSO4) will start to precipitate from the lake water and add sulfur to the lake sediments. The variations of % sulfur in Figure 12 match the variations in oxygen isotopes closely. Corroborating one paleoclimate proxy with another is an important check on proxy records and gives us more confidence in them.
Distinct peaks in these two proxies reflect times of aridity on the Yucatan Peninsula. The most arid time of the last 2000 years occurred between 800 and 1000 AD, coincident with the Collapse of the Classic Maya civilization. A newer high-resolution analysis of rainfall proxies from the Cariaco Basin narrows the timing of the most intense droughts to 810, 860 and 910 AD (Haug et al., 2003). These findings support a strong correlation between times of drought and a major cultural discontinuity in Classic Maya civilization. It is also important to remember that other factors such as overpopulation, deforestation, soil erosion and disease could have contributed to the demise of the Mayans.
Some important datasets related to drought and the collapse of the Mayan civilization:
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