This paper reports on the first and highly effective use of Light Detection and Ranging (lidar) technology to document Chaco roads, monumental linear surface constructions of the precolumbian culture that occupied the Four Corners region of the American Southwest between approximately AD 600 and 1300. Analysis of aerial photographs supplemented by ground survey has been the traditional methodology employed to identify Chaco roads, but their traces have become increasingly subtle and difficult to detect in recent years due to the impacts of natural weathering, erosion, and land development. Roads that were easily visible in aerial photography and on the ground in the 1980s are now virtually invisible, underscoring the need for new, cutting-edge techniques to detect and document them. Using three case studies of the Aztec Airport Mesa Road, the Great North Road, and the Pueblo Alto Landscape, we demonstrate lidar's unprecedented ability to document known Chaco roads, discover previously undetected road segments, and produce a precise quantitative record of these rapidly vanishing features.

An assembly of stone slabs on an isolated butte in New Mexico collimates sunlight onto spiral petroglyphs carved on a cliff face. The light illuminates the spirals in a changing pattern throughout the year and marks the solstices and equinoxes with particular images. The assembly can also be used to observe lunar phenomena. It is unique in archeoastronomy in utilizing the changing height of the midday sun throughout the year rather than its rising and setting points. The construct appears to be the result of deliberate work of the Anasazi Indians, the builders of the great pueblos in the area.

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