DescriptionCitadel Sink Wupatki National Monument.jpg
English: Citadel Sinkhole at Wupatki National Monument, with the San Francisco Peaks in the distance looking southwest. The sinkhole is formed by acidic rainwater seeping through cracks in the surface. The rain dissolved the limestone below, causing the ground to collapse above. It is around 600 feet in diameter.
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Captions
Citadel Sink at Wupatki National Monument, with the San Francisco Peaks in the distance looking southwest.