The report by Sofaer of a rock art solar marker at Fajada Butte in Chaco Canyon was followed by many reports of solar interactions with rock art on important seasonal days. A database of such observations is being maintained to assess such matters as the geographical distribution, preferred glyph type, and frequency. In spite of the 219 observations reported at 45sites by 29 different observers, the data remain inadequate for substantial conclusions. Observer selection effects and inadequate geographical coverage demand more data for meaningful conclusions to be drawn.
Many glyphs undergo sensitive, distinctive interactions on more than one seasonal day.
Few of the shadow-casting surfaces show evidence of human modification. Below is a map of observations included in the database from which the above statistics were derived.