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Paleo Slide Set: Low Latitude Ice Cores: High Resolution Records of Climatic Change and Variability in the Tropics and Subtropics
ECM Data at Quelccaya using decadal averages of data from Thompson et al. (1988).
Another intriguing finding in the Quelccaya record is the discovery of two pronounced peaks in the electrical conductivity and particulate data. Electrical conductivity measurements (ECM) vary with the acidity of the core sample, providing information on alkaline dust content. Particulate measurements also quantify the amount of dust in a given core layer.

The two pronounced peaks centered at 600 A.D. and 920 A.D. suggest pre-Incan agricultural activities on the altiplano. While killing frosts occur here even in summer, hardy tubers such as potatoes and cold-adapted chenopods like quinoa are well suited to the altiplano environment. The existence of an extensive pre-hispanic system of raised fields in this region of the altiplano and the increase in dust inputs evident in the Quelccaya record suggest that pre-Incan peoples may have placed large portions of the altiplano under cultivation with tubers and grains. It is unlikely that climate change alone could produce such marked signals in the ECM and particulate records; well before the present millennium, it seems, mankind was already making its mark on the Andean environment.

Photo Credits:
Thomas Andrews
NOAA Paleoclimatology Program and INSTAAR, University of Colorado, Boulder

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Last Modified: 12 October 2001

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