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Chaco Canyon is full of possible archaeoastronomical markers and alignments. One is a spiral petroglyph on the rock face high above Una Vida, an unexcavated site accessible via a path behind the Visitor Center.
I accompanied G.B. Cornucopia, park ranger, and Elizabeth and Amy, writing professors from Kansas, to watch the noontime sun's shadow move across the spiral for three consecutive days around spring equinox. Elizabeth is helping do some research regarding the various markers at Chaco and elsewhere, so this was of particular interest to her.
The photo above with G.B., Amy, and Elizabeth shows the petroglyph we were watching, far up and to the right on the cliff face behind them.
We took successive photos to note the movement of the shadow from the lower left, through the spiral, and off to the upper right. To give you some perspective, the time between the two closeup photos of the petroglyph is 11.5 minutes.
Each day it looked a little different in position and sharpness. But we all agreed it certainly could be an equinox marker. The movement through the center of the spiral was unmistakable.
The Chacoans could have tracked the movement and used it to determine time to plant, when the days would begin to be longer than the night, and so on.
We had many questions, too:
- What caused the shadow that moved across the petroglyph?
- What was their process for creating the spiral petroglyph in the rock, and ensuring it related to the movement of the sun?
- How did they create these pecked drawings in the rock, in days when there were no such things as erasers or the delete key?
- What about all the other designs on the rock face? What did they mean?
More on these questions in the next post.
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