Three Rivers Petroglyph Site, Otero County, New Mexico, United States

Three Rivers petroglyphs

About AD 200 to 1450 (Jornada Mogollon, by the land manager)

Dark basalt boulders, pecked with a light spiral and a horned four-legged animal, and desert shrubs standing between them. — Boulders at Three Rivers. A spiral and a horned animal have been pecked through the dark surface into the lighter rock beneath. The ridge holds more than 21,000 images of this kind. Dusty Matthews, CC BY 2.0. Shown unedited.

Twenty-one thousand pictures on one ridge of desert boulders, animals and masks and spirals, pecked by Jornada Mogollon people who lived right beside them. Someone has watched a shadow walk across a spiral on the solstice. The agency that keeps the site does not call the ridge an observatory, and the sheer number of pictures is why a shadow can be found.

Why this is extraordinary

A basalt ridge above the Tularosa Basin carries more than 21,000 petroglyphs, masks and animals, hands, insects, geometric marks, and spirals, packed onto about 50 acres. The Bureau of Land Management attributes them to Jornada Mogollon people and places the carving between about AD 200 and 1450. A village sits beside the ridge. The same figures turn up on that village’s artifacts, which is why the pictures and the houses are given to one tradition rather than to a hand nobody can name.

The rock was not cut away in relief. The dark skin of the boulder, desert varnish, was pecked off with a stone, and the mark is the lighter interior left behind. It is a durable way to draw, and an ordinary one across the Southwest. What is not ordinary is the number, gathered in one place, next to the houses of the people whose style the pictures match.

A field report describes spirals on this ridge that a shadow crosses at the winter solstice, or as the day goes on, and reads the place as somewhere the sun was watched. The land manager’s public account lists the images and never describes an observatory. The catch is the count. Among 21,000 figures, some spirals are going to meet a shadow on a notable day. A recorded meeting is only an observation, while an instrument is the further claim that someone put the spiral there for that meeting. The pictures are the monument, and the calendar is the part you still have to weigh, thin as it is.

Why it matters

If the spirals are sundials, Three Rivers is a Mogollon instrument as well as a gallery, and a few stones would carry a calendar the rest of the ridge does not announce. If they are not, the place is still one of the densest gatherings of rock art in the Southwest, dated by a village rather than by a guess at the sky. The problem of chance is the size of the gallery.

Jornada Mogollon is the archaeological culture of the Tularosa Basin and its neighbours in these centuries, part of the wider Mogollon tradition, with pithouses and, later, pueblos, and with painted pottery. Desert varnish is a thin dark coat of clay, manganese, and iron on the rock. A petroglyph is a mark made by taking that coat away, not by adding paint. The Bureau’s visit page says about AD 200 to 1450, while another Bureau note says about 500 to 1450. The pictures themselves are rarely what anyone radiocarbon dates. The village, and the imagery it shares with the ridge, is the clock.

Photo tour

2 photographs, unedited. On a phone, swipe the row. Choose one to look closely.

A brown boulder carrying a pecked spiral near the top and a four-legged animal below, with dry grass in front. — Another face of the ridge, a spiral set above a quadruped. Spirals are common on these rocks, and a spiral is the form a shadow claim needs. Nothing in this photograph shows a shadow being measured.jaygannett, CC BY-SA 2.0

What is still unexplained

These sit beside the consensus account, with the same visual weight. None of them is marked solved.

The attribution that holds A village and a ridge with the same pictures The land manager’s archaeologists point to a partly excavated village beside the petroglyphs, and to the same iconography on the things that village left behind. That is why these count as Jornada Mogollon images and not a later traveller’s doodles, though historic initials do sit on rocks in the drainage and make a separate, obvious layer. Water was easier to come by then. Corn, beans, and squash were grown, and three streams came down off the Sacramento Mountains nearby. The ridge is not a sign left in an empty wilderness. It is the picture-ground of a valley people lived in, and the opening date is not one hearth under one boulder but the span of the culture the Bureau assigns.

Reported, not the site’s account Shadows on spirals A research note on this ridge describes spiral motifs that interact with sunlight, including a shadow that passes the halfway point of a spiral at the winter solstice, and it says at least four stones do something of the kind through the day or through the year. That is a specific observation and it deserves to be said out loud, though it remains one reporter’s reading and does not appear in the Bureau’s list of masks, sunbursts, wildlife, handprints, and geometry. A sunburst is a picture of a sun-like mark, and a picture of a sun is not a measurement of the sun. With more than 21,000 images, the chance that some spiral meets a solstice shadow is not a small one. A fair test would say how many spirals were watched, how many did nothing that day, and whether the shadow was predicted before the visit or noticed once someone was standing there. Those numbers are not in the public account used here. Until they are, an observatory is only a possibility resting on a very large gallery.

Location and dating

Location: The Three Rivers Petroglyph Site, on public land in Otero County, New Mexico, north of Tularosa, between the Tularosa Basin and the Sacramento Mountains. A short trail follows the ridge, with a village trail nearby.
Period label: Current consensus — open to revision Jornada Mogollon, as the Bureau of Land Management places it, between about AD 200 and 1450, with a second Bureau statement that begins nearer AD 500. The pecked marks are not each given a year of their own.
How this dating was done: Dating here rests on Style and context. Village ceramics and the motifs they share with the ridge are a typology. A shadow on a spiral counts as archaeoastronomy only when the match is tighter than chance and was not picked out after the fact. Radiocarbon would need organic material in a layer that seals one particular pecked face, and these boulders, standing in the open, rarely have that.
What could change it: A published count of the spirals someone watched and the spirals that failed, with the horizon and the day named in advance. Or a crust, itself dated, that formed over a pecked line and so gave a minimum age for that one image.

Published ranges, drawn as bars. A bar is a claim about a span, not a point.

Bureau range

200 CE1000 CE1450 CE

Bureau range. The span the visit page gives for Jornada Mogollon carving at the site, while a later Bureau note starts nearer 500. What differs is the beginning of the culture, not a date stamped on one animal.

What is actually there

More than 21,000 petroglyphs, spread over about 50 acres of basalt.
The marks take in masks, animals, hands, insects, plants, and geometric designs, each pecked through desert varnish.
Beside the ridge, a village uses the same imagery.
A field report describes shadows, at the solstice and in daylight, crossing several spirals.
The public guide from the land manager does not present the ridge as an observatory.

Open questions

Question	Status
Was any spiral placed so a shadow would cross it on a day someone had chosen?	Open, and thin. One reported crossing is not a calendar until the misses are counted.
Why gather so many images in a single place?	Open. A village next door makes a long local use more likely than a single ceremony. It does not say what the masks were for.

The current narrative

Where publication stands today. It is the best-supported reading, and it is open to revision. It is not a verdict.

The current narrative — open to revision

Jornada Mogollon pictures beside a village

Jornada Mogollon people made the petroglyphs across several centuries, in the place where they lived. The subjects are the ones the Bureau lists. What an animal, a mask, or a piece of geometry meant is not captioned by the people who pecked it. A sunburst is a picture, and it is not yet an instrument.

What supports this

More than 21,000 images, worked in a style the land manager identifies as Jornada Mogollon.
A village whose artifacts carry the same iconography.
Pecking through varnish, the technique used here, is the ordinary technique of Southwestern petroglyphs.

What pushes back

The Bureau’s own pages do not agree on whether the span opens near 200 or nearer 500.
Historic initials show that later people marked the drainage too. Style is what separates those marks, and style can be argued over.
No caption tells a visitor today whether a mask is a being, a neighbour, or a story.

What would settle it

The culture holds, and so does the place. The fine date of any single glyph does not, and it does not need to, for the site to be what the Bureau says it is.

Emerging narratives

Other published readings. Each may be right. None is adopted here unless the evidence carries it.

An emerging narrative

The spirals are solar markers

Certain spirals were cut so that light and shadow would mark the solstices and the passing of the day. On that reading the ridge is an observatory as well as a gallery.

What supports this

A field report of shadows crossing spirals, one of them at the winter solstice.
Spirals and sunburst forms are both present, so the sun is at least a subject someone pictured.
Other Southwestern sites carry stronger light-and-shadow marks, still debated, so the idea is not a stranger to the region.

What pushes back

So many images make an accidental crossing likely.
The account published for visitors does not include the claim.
A shadow noticed during a visit is weaker than a shadow someone predicted and then found, with the failures listed beside the hits.

What would settle it

Worth a paragraph, and not the centre of the visit. The weight would shift if a count of hits and misses were published and the hits were too many for the number of spirals.

Should the current view be reevaluated?

Consensus holds well

The ridge is secure, and so are the number and the Jornada Mogollon attribution. What is not secure is the astronomical reading, a reported shadow on a few spirals, set against a gallery large enough that such meetings can happen by chance, and left out of the land manager’s account. Weight stays with the pictures, and with the village beside them.

What drives this

More than 21,000 images, pecked into the rock.
A village that repeats the same motifs.
A report of a solstice shadow that has never been adopted as the description of the site.
How easy it is to find a match when the marks are this numerous.

This is the museum’s own weighing of the evidence. It is not a visitor vote, and it is separate from the slider.

Weigh it yourself

Anonymous. Nothing here is stored except on this browser. Your lean does not change the assessment beside it.

Jornada Mogollon pictures beside a village Unsure The spirals are solar markers

If the contested reading is right

What would follow if a reading that is not the consensus turned out to be true, and what could settle it. This explains the stakes. It does not adopt the reading.

A few spirals were real solar markers

Those particular stones would be instruments set inside a much larger body of pictures. The rest of the ridge would not, on its own, become a calendar. The village would still be what dates the place.

Why it is still worth a test

A pre-registered watch of named stones, on the solstice, with every spiral that does nothing written into the report.

Sources

Three Rivers Petroglyph Site Bureau of Land Management

Image credits

Boulders at Three Rivers. A spiral and a horned animal have been pecked through the dark surface into the lighter rock beneath. The ridge holds more than 21,000 images of this kind.. Dusty Matthews, CC BY 2.0. Shown unedited.
Another face of the ridge, a spiral set above a quadruped. Spirals are common on these rocks, and a spiral is the form a shadow claim needs. Nothing in this photograph shows a shadow being measured.. jaygannett, CC BY-SA 2.0. Shown unedited.

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