Finding Order Out of Chaos: A Statistical Analysis of Nine Mile Canyon Rock Art

Abstract

<b>Introduction: The Nine Mile Paradigm</b><p> Nine Mile Creek (which is actually about 144 km long) is a perennial west-to-east tributary of the Green River, itself the largest tributary of the Colorado River and part of the greater Colorado Plateau, the largest drainage system in the western United States. It is a high-desert region and generally arid, with an agricultural zone in the valley bottom that receives less than thirty centimeters of rain annually—an amount insuffi cient for agriculture without irrigation. Nine Mile Creek is a small stream, generally two to four meters wide and no more than twenty to thirty centimeters deep, that is fed by high plateau spring snow melt and small springs along its entire course. One of only four flowing water sources in the West Tavaputs Plateau, the creek is a predictable and consistent source of water even during the worst droughts. <br/> Nine Mile Canyon, through which the Creek flows, probably has more rock art than any other place in the continental United States. Most of those who choose to work in Nine Mile Canyon in eastern Utah are awestruck by the sheer quantity of images, and in some cases by the remarkable skills and fearlessness of the ancient artists, given that images can be found along the narrowest of cliff ledges where one slip meant certain death.<br/> To date, archaeologists have thoroughly inventoried about 10 percent of the canyon, where they have documented some 1,200 prehistoric sites of all types, mostly rock art sites and agricultural residences and hamlets typically assigned to the Fremont Complex (AD 500–1300) (e.g., Simms 2010). It is estimated that a complete inventory of the canyon would result in the identification of about ten thousand prehistoric sites, most of which would have rock art features, perhaps with as many as 75,000 to 100,000 images in total. About half of the rock art clusters are found near the canyon bottom, and because of an access road in the bottom of the canyon these images are well known to the public and rock art researchers and touted by tourism boosters as "The World's Longest Art Gallery." The creek has eroded the soft Tertiary-age sandstone of the Green River Formation, creating a stair-step series of cliffs rising 300–400 meters above the valley floor. These cliff faces are often quite smooth and patinated with accretions of red-to-black iron oxide, popularly referred to as "desert varnish," that have proved to be an attractive canvas for prehistoric rock artists. The rock art is found along the lower 72 kilometers of the canyon, starting at an elevation of about 2,040 meters and continuing uninterrupted to the creek's confluence with the Green River at 1,400 meters above sea level.<br/> Since 2006, the Colorado Plateau Archaeological Alliance (CPAA), a nonprofit working to protect cultural sites on public lands in the American West, has conducted systematic inventories of the canyon, establishing uniform methods for documenting, organizing, and describing prehistoric rock art consisting of petroglyphs (by far the most common rock art) and pictographs (few in number and preserved only in sheltered settings).</p>