Archeoastronomy in Stone

The Ancestral Pueblo people carved petroglyphs and painted pictographs to follow the cycle of the sun, moon, and stars; equinoxes and solstices; and to document extraordinary celestial events. They tracked these changes in relationship to important cultural events surrounding the seasonal cycles and their associated ceremonies, such as for planting. Communities even oriented settlements, buildings, and architectural features to mark astronomical time. Examples of these include Sun Temple Sun Temple at Mesa Verde National Park, the Aztec West great house and Great Kiva at Aztec Ruins National Monument, and the complexes at Chaco Culture National Historical Park.

Archeoastronomy (or archaeoastronomy)

The study of the ways people in the past understood phenomena observed in the sky, the uses for these phenomena, and their significance and role in culture.

Equinoxes and Solstices

The sky turns like clockwork. By observing its movements, people in the past predicted and prepared for seasonal changes.

For instance, an equinox occurs twice each year, in March and September, when the Sun crosses the Earth's equator. On the day of an equinox, there is an equal amount of day and night time. Marking the equinoxes helped people orient to the necessities of the coming fall and spring seasons.

Likewise, a solstice marks the beginning of winter and the return of light as the days lengthen in late December. In June, the summer solstice is the longest day of the year. On each solstice, the Sun appears to rise due east and set due west, a phenomena captured in architecture and rock markings.

Holly House

A spiral and a set of concentric circles near Holly House at Hovenweep National Monument mark the summer solstice. At the solstice, a sun beam enters a narrow opening across from the panel to bisect the petroglyphs.

Two spiral petroglyphs near Holly House. NPS photo.

Puerco Pueblo

The Puerco Pueblo Trail at Petrified Forest National Park leads through Puerco Pueblo to a boulder featuring a small spiral petroglyph that marks the summer solstice.

Puerco Pueblo solar marker montage. NPS photo.

On the morning of the solstice, a shaft of light projects onto the boulder and travels down the side to touch the center of the spiral.

Solar marker at Puerco Pueblo. NPS photo.

Fajada Butte

The Sun Dagger at Fajada Butte at Chaco Culture National Historical Park is believed to have marked summer and winter solstices and equinoxes. Depending on the time of year, a spot of sunlight started to fall at the spirals, then lengthened into a “dagger” shape. The dagger extended across the spirals until disappearing. Unfortunately, the dagger of light no longer crosses the center the spiral as it once did, because erosion due to foot traffic has caused the slabs to shift out of position. The site is no longer open to the public.

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Celestial Events

Petroglyphs and pictographs also marked extraordinary celestial events. Some of these events were recorded by cultures around the world.

A pictograph on the Penasco Blano trail at Chaco Canyon may depict a star that exploded on July 5, 1054. The supernova appeared in the constellation Taurus next to a waning crescent moon. It could be seen during the day for over three weeks. The pictograph shows the waning moon and the exploding star. The hand may point to the horizon where the supernova rose an hour and forty-five minutes before sunrise. The concentric circles may represent the sun before it rose or, possibly, a comet.

Pictograph depicting an exploding star. NPS photo.

On July 11, 1097, a total solar eclipse took place in the Southwest. A petroglyph at Chaco Culture National Historical Park may represent the eclipse. It shows a filled-in circle with squiggly lines extending around its edge and a small, filled-in circle to the upper left. It may illustrate the sun in total eclipse and the planet Venus.

Squiggly sun petroglyph. NPS photo.

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Preserving Rock Markings

Communities in the past marked rock to keep track of time and the changing seasons to know when to plant, celebrate, rest, and remember. Today, many people – including tribal descendants and park visitors – find personal and cultural meaning in them.

Petroglyphs and pictographs are fragile and irreplaceable. Do your part to help the National Park Service preserve and protect these precious images. If you encounter them on a visit to a national park, please take photographs, but do not disturb them or the surrounding rock faces.

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Learn More

Petroglyphs and Pictographs, National Park Service

Archaeoastronomy (Aztec Ruins National Monument)

I Didn’t Know That! -- Winter Solstice (National Park Service)

Night Skies (National Park Service)

Types of Eclipses, Natural Phenomena (National Park Service)

Where this belongs

• Aztec Ruins National Monument
• Chaco Culture National Historical Park
• Hovenweep National Monument
• Petrified Forest National Park

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