Thursday, March 20, 2008

Impressive Angkor

We've all seen photographs of Angkor Wat, the spectacular 12th century Khmer Temple in Cambodia. I was surprised to learn that Angkor Wat is just the tip of the iceberg-- that it was the center of an enormous, low-density urban complex whose size (1000 square km) rivaled large modern day cities.

Right before Spring Break, I attended a presentation by Roland Fletcher, an archaeologist from the University of Sydney who is leading up the Greater Angkor Project. This 10-year study is bringing new technologies to bear on the large questions surrounding the city of Angkor.

Using airborne side-looking radar (and other imaging from space), amazing features were revealed. From the presentation summary:
So far the project has mapped the extent of the water management system, has located key water management structures and has identified the dispersed pattern of occupation along canals and roads and on house-mounds. The demise of the urban complex now has to be reappraised because it was apparently functioning into the 16th century, later than the generally assumed sack in the early 15th century CE.
The scope of Angkor is startling. If you take a look at the feats of engineering the Khmer accomplished, one can't help but be amazed. The second photo in this post (click it for a larger view) is a satellite view of the temple of Angkor Wat, its grounds, and the large, square moat which surrounds it. You can see that the temple is dwarfed by the moat, and Dr. Fletcher tossed up a slide that showed the area inside the moat is larger than any Mayan city.

Not stopping there, you need to see the map of the entire Angkor complex (the 3rd image). The very center square on the map is Angkor Thom, the royal forest. Just below it, a tiny blue square represents the moat at Angkor Wat.

The long, rectangular blue features are man-made water reservoirs which supported the irrigation of the entire area. The West and East Baray (the two largest) are 8 kilometers in length. The NASA Earth Observatory has a large AIRSAR image of the Angkor region, plus an accompanying GIS map of all the archaeological features and sites.

What have they determined so far? It looks like the earlier theory (by Bernard-Philippe Groslier) that the large reservoirs were primarily for irrigation are correct. The radar imagery show the remnants of rice fields covering the entire region from the lake to the mountain foothills. A river was diverted to fill the reservoirs, and to irrigate the landscape. Excavations of old water channels has revealed evidence of heavy flooding (including substantial deposition of sand), which likely overwhelmed their system. It is possible that the deforestation of the area for conversion to agriculture, combined with the re-routed natural water channels, may have led to a large-scale ecological disaster.

One of the principal investigators (Damian Evans) was the lead author on a paper last year that reported on their comprehensive mapping (see below).

Additional resources:

1. Wikipedia has a nice overview of Angkor's history.

2. Evans, D., Pottier, C., Fletcher, R., Hensley, S., Tapley, I., Milne, A. and Barbetti, M. 2007. A comprehensive archaeological map of the world’s largest pre-industrial settlement complex at Angkor, Cambodia. Proceedings of the National Academy of Sciences of the United States of America. Vol. 104 no. 36, pp. 14277-14282

3. The American Museum of Natural History has a nice animated overview of the current findings at Angkor.

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