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Drought and the Ancient Maya Civilization


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Image of Mayan pyramid
Originating in the Yucatan Peninsula, the ancient Maya civilization occupied a vast area of Mesoamerica between the time period of 2600 BC and 1200 AD. Constructing thousands of architectural structures and developing sophisticated concepts in astronomy and mathematics, the Maya civilization rose to a cultural florescence between the years of 600 to 800 AD. Then, between the years of 800 and 900 AD, many southern cities were abandoned and most cultural activities ceased. This period is known by archaeologists as the Collapse of the Classic Maya civilization. The Maya, never able to regain their cultural or geographical prominence, were assimilated into other Mesoamerican civilizations until the time of the Spanish Conquest in 1530 AD.

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.

Proxies from Lake Chichancanab showing changes in regional precipitation-evaporation

Figure 12.Scientists reconstructed changes in the balance between precipitation and evaporation using the % sulfur of sediments and the oxygen isotopes of shells of gastropods and ostracods from Lake Chichancanab on the Yucatan Peninsula (Hodell et al. 1995).

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:

Next: Conclusions



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