Archaeologists from the Jagiellonian University have found out that some of the rock drawings made by Native Americans about 800 years ago in the canyons located in the border region between the US states of Colorado and Utah were linked to astronomic observations, such as determining the dates of summer and winter solstices. The pioneering archaeological research in this field has been led by Dr Radosław Palonka from the JU Department of American Archaeology.
Since 2011 the JU Institute of Archaeology has been running an archaeological project in Mesa Verde region located on the border of Colorado and Utah. The area is famous to both archaeologists and tourists for the Pre-Columbian Pueblo culture settlements built in rock niches or carved into canyon walls and for numerous ancient works of rock art. The research is the first Polish independent archaeological project in the United States and one of the few such European projects in the region.
The sites studied by the JU researchers contain remains of several dozen small settlements centred around Castle Rock Pueblo, built in the 13th century AD by Pueblo people. So far, Dr Palonka’s team have discovered previously unknown cave galleries containing murals and petroglyphs from various historical periods.
During their studies, the archaeologists started to speculate, based on the analogies to several other sites in the South-West USA, whether some of these stone carvings hidden in rock recesses could be used by the ancient Pueblo people to determine the dates some important days of the year, namely summer and winter solstice as well as spring and autumn equinoxes. Two such sites have been studied so far. At the first one, centred around a rock niche with remains of several buildings from circa 800 years ago, petroglyphs were carved on a flat rock wall facing south, shaded by an overhanging rock. The panel consists of three different spirals and several smaller elements, such as rectangular motifs and numerous hollows.
“Our observations revealed a unique phenomenon, particularly visible during the sunset of the winter solstice on December 22, when the sun rays and shadows move across the middle part of the panel with petroglyphs, going through the subsequent spirals, longitudinal grooves, and other elements. To a much lesser extent, the phenomenon is also visible during the spring and autumn equinox. The interaction between light and shadow as well as the moving of sun rays across the entire panel is already visible some time before the winter solstice, as well as several weeks afterwards. We have not seen this phenomenon during the remaining part of the year”, explains Dr Palonka.
Similar illumination of petroglyphs by sun rays in specific periods of the year has been observed at another site in Sand Canyon. What was different was that the petroglyph was regularly lit by sun rays only in the morning and early afternoon during the summer solstice. The researchers are planning to continue to study the rock art’s relations with astronomy.
The JU archaeologists’ conversations with members of Hopi tribe, who are the descendants of Pueblo people, have confirmed that the spirals were most probably used as a sort of calendar. As pointed out by Dr Palonka, similar ethnographic studies from the 19th century also suggested the existence of solar calendars: both the horizontal ones, based on watching sunsets and sunrises over certain mountains, passes and valleys, and those related to observing sun rays shining on petroglyphs during solstices or equinoxes. It is also worth noting that summer and winter solstices are still of great religious importance to contemporary Pueblo groups from Arizona and New Mexico, providing framework for rituals and celebrations related to key farming activities, such as sowing and harvesting, as well as the preparations to these crucial tasks.