Solar eclipse from Tumamoc Hill, Sunday, May 20, 2012

Tumamoc’s Sun Arrow

Summer Solstice Stone from Paul Mirocha. Watch it on Vimeo.

Wednesday morning, June 20, 2012
(Official solstice was placed at 7:09 pm that afternoon.)

long-horned beetleI got up at 4:25. Through the kitchen window I could see the first glow of light in the east, and the two morning stars. Mercury was visible, and just below it, the larger planet which must be Venus. That seemed auspicious as I made a cup of strong coffee using a French press. The planets had all but faded from sight in the sky brightened and I reached Tumamoc Hill.

Suzie and Paul Fish, Cynthia Anson, Tumamoc Program Coordinator, and I met at 5am at the Desert Lab parking lot and drove together up to the summit. The calendar stone they were looking at is on the south side of the hill where there are some very well preserved trincheras, pithouse foundations, and rock art. And the view on top is spectacular: the horizon of mountains is visible all 360?. (I made a note to come back and make a 360? panoramic photo)

Saguaros nearby were laden with split and ripened fruit, the bright red insides of the husks aimed at the sky. The ripened fruit is calling the rain, as O’odham saguaro harvesters will tell you. The first sound I noticed was a loud buzzing?severallarge golden male carpenter bees swarmed around and within a lycium bush. An orange long-horned beetle (Trachyderes manidbularis) sat in one branch of the same bush, all waiting for a female to wander by. These insects were hill-topping. High places are the most convenient place for singles to meet, more likely get lucky, and mate. I took a few deep breathes?I had heard that the male carpenter bees let out so much pheremone that a human could detect it; it smelled a bit like like roses. I?d like to think I got a whiff of bee pheremone, but I could not be sure.

The four of us spent a couple of hours up there in total, watching as the sun rose, a beautiful red ball that could be easily looked at for a few seconds, from a notch between two ridges on the horizon, the eastern edge of the Catalina Mountains, about 5:30. (Officially sunrise was 5:18am) The hill was bathed in pink light. Paul took a photo of the sun where it appeared on the horizon.

Contemporary Native Americans landmarks on the horizon to determine where the sun rises or sets at solstices and equinoxes. Obviously the point where the observer is standing are made is just as crucial and must stay the same for those notches on the horizon to be meaningful. Tumamoc seems to be the chosen place. It was easy to see why. Besides the beauty of the views, one could see all around, 360?, even to Picacho Peak, 50 miles away. One can see Baboquivari Peak, sacred mountain and center of the universe for the O?odham people. At one point, just the tip of Baboquivari’s great cathedral-like dome was lit by the sun, which gradually moved down, expanding as it lit up the whole peak. Every mountain peak and range on the horizon is visible and they all probably had ancient names, traditional significance, and powerful poems written about them, if these ancient ancestors were anything like the hisatoric natives of the Sonoran Desert.

Those points on the horizon would suffice to note the timing for the all-important cycles of ceremony and planting of seeds. Historical and modern Pueblo and O’odham people use this method of sighting along a point on the horizon. It fact, it is probably more accurate than using a calendar stone and rock alignments to mark a solstice. Yet, for their own reasons, the Hohokam chiefs, priests, or shamans who set up these calendar stones went further than what was required. They added some significance, made the shadows and beams of light on this hilltop into a performance, a ceremony of sorts. So I thought.

Just after 6am, the sun was high enough that we could see we started to see the beams of sunlight and shadows moving on the petroglyph-covered rocks around us. Sure enough a dagger or more likely, an arrowpoint of light slowly formed at the western edge of the flat calendar stone and moved towards the proposed ?calendar? glyph?a design with a series of concentric circles. There are others like it, at least one similar symbol made of concentric circles nearby, and one on the eastern edge of the summit, but none of those showed any obvious meaningful activity at that time.

Tumamoc sumemr solstice stone
Sun Dagger effect on summer solstice calendar stone, just after dawn on June 21, 2012. Note the diagonal incised line, part of the petroglyph, which aligns precisely with the bottom of the arrowhead of light. The incised line looks newer than the petrogyph is is drawn over.
Tumamoc light arrow on petroglyph
Notice how the rock in the foreground makes the shadow that forms the straight edge of the left side of the light arrow as it passes through the calendar petroglyph. This large rock was apparently intentionally positioned to do this work. It would have required several people to lift. I could not find the rock that formed the other side of the triangle–it originates in a complex rubble of boulders east of the calendar stone.


As we watched over the next half hour, a hard edged triangle of light passed through the center dot of the target-shaped rock art motif. The tip of the arrow passed through the innermost circle, but not the central dot as we expected. Though the lower edge of the arrowhead did pass through the center of the glyph. There was no doubt about it. This was not an accidental shape formed by light and shadow on the tumbled boulders, like the others all around us. One of the edges of the of the nicely formed light arrow was clearly formed by the top edge of a long flattened boulder which had clearly been purposely placed there and wedged in place with other rocks.

The shaft of light was like an arrow point, an artifact and symbol clearly very familiar to the minds of these people. Stone points were often used as sacred objects or objects of prestige in themselves. Paul explained that caches of thousands of points have been found in some of their archeological digs with no obvious practical use. Many stone points were left as offerings in burials. Some months ago, Paul and Suzie had shown me a clearly ceremonial obsidian spear point, extra long, fragile and not utilitarian, found in the large circular kiva excavation, now right under the road and near where we parked our car. Like everyone else, I rubbed the rounded areas on the point that had been smoothed by countless human fingers before us.

As we watched, fragmented sunlight slowly crawled and bent over the rocks, many covered with rock art. Suzie pointed out how some of the petroglyphs, usually indistinct, were highlighted or spotlighted under certain light. Insignificant designs looked like electric signs at the right time of day. Maybee the designs were meant to be noticed at those times. As we looked around, it was also apparent, if you thought about it, that some glyphs could be easily seen by many people and others by only one a few. It all depends on their size, placement, and the space around them for viewing.

Suzie commented that maybe the process making of the rock art was the important thing, not the final product, as we might expect in our culture. We should not see them through our own cultural lens. She would like to do some research on the distances and sizes of the rock art, the viewing spaces, and make estimates on how they were meant to be seen.

petroglyph and rock shadows
The large flat rock wedged vertically into place at bottom center of this photograph makes a shadow that grows and enters the small niche or hole in the rock at the upper left of center.

A nearby boulder complex caught our attention as we stood there for the twenty minutes or so that the sun arrow took to travel through the glyph and dissolve again into another fuzzy bit if light and shadow. There was a large flat rock to one side of it that looked like it had been moved there, just like the one mentioned earlier to the east of the calendar stone. It would have taken several people to place it, wedge it between other rocks, and secure it. There was at least one other rock wedged in there to make the whole alignment unmovable. The larger boulder itself formed something like? a natural table, or shelf, or altar, where other objects could have been placed. On the horizontal surface of this shelf, the aligned rock made a long, phallic looking shadow that inexplicably lengthened as the sun rose until it touched a small niche, cleft, or hole in the rock. There were many such holes in the rocks, all natural, but also apparently smoothed by hand around the edges, giving them significance. Just above the natural shelf a sun symbol was carved around one of these holes. Other glyphs appeared on the rock or nearby, an archer, a complex “shaman” looking figure with its arms raised.

Then that long shadow began to shorten, as would be expected of a shadow as the sun rose higher. The lengthening of the shadow baffled us and I mean to go back and watch it again. I asked the others if they had see that shadow lengthen, then shorten again. ?Yes, I think so,? they said. Possibly this effect is caused by the curvature of the plane of the rock forming the shelf.

There were so many things happening with the sun and shadows on that summit that it could take many years of repeated observations to sort the random from the designed shapes. And shapes that were indeed random and out of focus might form a design only if seen at the right time of day and year. There might also be some effects reserved for sunset, as the solstice windows in the big house ruin at Casa Grande. But archeologists are watching the spiral and target-shaped designs for possible calendar activity.

The event was like what we moderns would call a piece of conceptual art. An idea, ephemeral and existing only in mind, expressed through a minimal arrangement of stones that was only visible for a 20 minute period once a year. It’s something environmental sculptor Andy Goldsworthy might do or at least appreciate.

Our brains are wired exactly the same as the Hohokam a thousand years ago. But our world view is so different, it is probably impossible for us to see exactly what they saw; our basic beliefs about what we see, our “operating systems” are very different. It might help our understanding if we could live in a tent or pithouse on top of Tumamoc Hill for a year. We’d begin to see a different world. Still, I felt that we had made a thought connection, however small and dimly understood, with an unknown person, or more likely a long lineage of people,?living centuries ago and with a vastly different conception of the world than we have today. They left this and other sun signs without explanation, for us to ponder and puzzle over, in the rocks on top of Tumamoc.

Maybe that is enough: to observe and to contemplate a place from multiple viewpoints over large time scales.


Notes: I went back the following morning, June 21 because the actual astronomical solstice was in the late afternoon of the 20th, and took the time lapse sequence shown above, snapping a frame every 30 seconds. A week later I went to the same spot by myself to see if there were any changes that would show how accurate the marker was for the actual solstice. Unfortunately the monsoons had begun and a bank of low clouds diffused the direct sunlight during the crucial time period.

There is a famous sun calendar petroglyph discovered in 1977 by artist Anna Sofaer at Fajada Butte near Chaco Canyon. The Anasazi ruins on Fajada Butte are around the same age as the Hohokam Classic period village on top of Tumamoc Hill. The Chaco site was called the “Sun Dagger” because of the long narrow blade-shaped sunbeam that moved through a spiral-shaped petroglyph there. The calendar stone on Tumamoc has many similarities, but the shape is more triangular like an arrowhead. Read more here.









3 thoughts on “Tumamoc’s Sun Arrow

  1. Hi, how were you able to access the petroglyphs on Tumamoc Hill? I’ve read online that you can’t hike to them because of private property. Is that accurate or can they be seen (with binoculars?) from a hike for pedestrians? Thanks!

    1. I had access to the site over the period of years that I was studying it with a permit. In 2021 I and even archaeologists were prohibited from the summit pending conversations with the O’odham Nation. I was working with an archaeologist to measure the accracy using sun angles and also verify some other aspects of the sun interaction that raised more questions. I wanted to document this before any more damage happens due to grafitti on the summit.

Leave a Reply

Your email address will not be published. Required fields are marked *