Chimney Rock National Monument is an archaeological site in the San Juan National forest located at the southern edge of the San Juan Mountains in southwest Southwest Colorado, about 20 miles west of Pagosa Springs and 30 miles east of Durango. The Monument covers seven square miles and preserves approximately 200 ancestral Puebloan structures, Chimney Rock is referred to as a Chacoan outlier because of its Chaco-style Great House Pueblo and associated archaeoastronomy. The name Chimney rock derives from one of the two sandstone pillars that rise from the top of a large questa. The Pictured Cliffs sandstone and underlying Lewis shale layers making up the pinnacles are what are left of a vast shallow sea that was pushed up 40 million years ago by volcanoes (Chronic and Williams 2002). Fossilized burrows of shrimp-like crustaceans, ophiomorpha, are found in the sandstone. Fossilized sea shells are found in both sandstone and shale layers. because the area is semi-arid, the questa top is sparsely covered the pinon pine, junipers, sage and yuccas, while the lower slopes are covered with ponderosa pine. Topographically, the Chimney rock questa is divisible into two sections; a lower and an upper mesa that are connected by a narrow causeway. On the upper mesa, at 7,600' elevation, sits the Great House Pueblo, while the lower mesa contains the majority of the prehistoric structures. The lower meas is bisected by a deep ravine, named the Chimney rock Raving by Frank Eddy (1973:1977).