Posted by: Johan Normark | May 8, 2009

Climate and the “Maya collapse” pt 3: Proposed palaeoclimatic causes

Palaeoclimatological studies in the Maya area tend to see climate as a driving and deterministic force that directs the societal development (Brenner, et al. 2002; Folan, et al. 1983; Gill 2000; Gill and Keating 2002; Gill, et al. 2007; Gunn, et al. 2002; Hodell, et al. 2001; Hodell, et al. 1995; Hodell, et al. 2000). In recent years several palaeoclimatological studies have tried to explain both the emergence of hierarchical social formations (Hansen, et al. 2002), but particularly their “collapses” (Gill 2000; Gill and Keating 2002).

Central in the discussion of climatic change are sediment cores from Lake Chichancanab in the Cochuah region. These cores show long-term shifts in the availability of moisture during the Holocene (Covich and Stuiver 1974; Covich 1970; Curtis and Hodell 1996; Hodell, et al. 2001; Hodell, et al. 1995). A drying trend reached its driest phase between A.D. 800 and 1000 and it corresponds in time with the Classic “collapse” (Brenner, et al. 2002:149). However, the drought hypothesis has avoided the data from the Petexbatun area (Demarest 2004:107). Here the “collapse” occurred before the drought. The earliest sites to “collapse” were the ones located along the western rivers which make the drought hypothesis questionable. Gill and others’ (2007) later article claims to take this into account (A.D. 760).

The climate change is attributed to various causes. The El Niño phenomenon and its “sister” event, La Niña have been thought to play some role in the Prehispanic Maya area (Messenger 2002:159). However, no discernable regularity between El Niño and recorded Mexican droughts has been found during the twentieth century or in Colonial time (ibid:165). Solar intensity varies through time, at intervals of 208, 100, and 50 years (Hodell, et al. 2001). The 208-year cycle is the dominant one and droughts are known during the periods of high solar intensity (Brenner, et al. 2002:151).

Volcanoes have been blamed for several changes in the Mesoamerican history as they affect the weather, even far away from the eruption (Gill and Keating 2002:127). However, if this was used as an explanation for one or two events, that might be possible, but when Gill and Keating goes on to explain every single “collapse” in Mesoamerica by volcanic eruptions in other parts of the world, it clearly shows the model’s problems. For example, it is argued that the abandonment of the Late Formative site of El Mirador was the result of the eruption of Taupo in New Zealand. It is argued that the Classic “collapse” was a showdown in four acts (A.D. 760, 810, 860, and 910), which are correlated to volcanic eruptions in the Mesoamerican area (Popocatepetl and El Chichon) (ibid:135). Basically, just take an archaeological site whose abandonment you wish to explain, search the globe for a volcanic eruption that slightly predates this abandonment and there is no need to search for other explanations. My next post in this series will be focusing on some of Gill’s assumptions and his methodology.

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