Watching the Sun

Walls at Wijiji

Today is the winter solstice, and the seventh anniversary of this blog. I’ve traditionally posted about archaeoastronomy on these anniversaries, so I’m going to briefly interrupt my series on Crucible of Pueblos to discuss an interesting article on the evidence for astronomical observations at Chaco Canyon. There turns out to be some overlap, actually, which is interesting.

The article is by Andrew Munro and Kim Malville, who were also the authors of the article on building orientations that I talked about last year on this date, and it was published in the same special issue of the journal Archaeoastronomy in 2010. The content is rather different however. This article summarizes the evidence for specific locations in and around the canyon for which there is evidence of use as solar observation “stations,” including two sites which are newly identified here. (Worth noting here is that Munro left a detailed and interesting comment on last year’s post, in which he linked to his unpublished thesis which contains more detailed and up-to-date information on his approach to archaeoastronomy. I haven’t read it yet, so I’m focusing here on the published articles while recognizing that they don’t have the most recent information.)

Identifying viewing stations is more complex than simply demonstrating alignments, for a variety of reasons. For one thing, based on modern Pueblo ethnography, sun-watching locations were not necessarily marked physically with architecture, rock art, or anything else. This makes their archaeological identification difficult, and probably means that the stations that did happen to have physical markers are probably over-represented.

Identifying these stations also requires careful consideration of how exactly the observation process would have likely worked, what its specific purposes were, and how they could have been met. If, as Munro and Malville argue, the main role of these observations was to fix the dates of ceremonies marking key times in the year, there would have been a practical need to mark not just the date of the ceremony itself, but dates leading up to it which would have given time to prepare for it. Munro and Malville use the term “anticipatory” for stations that would allow prediction of an event in advance, and “confirmatory” for those that would allow observation of the date of the event. There would also need to be a system for communicating the information from the observation stations quickly and easily to other sites in the canyon and beyond.

There is also an important distinction between observation stations and shrines. The former were used for the practical purpose of making observations, while the latter were associated with those observations but used for ritual activities rather than observation, and often were not in locations from which accurate observations could be made. Munro and Malville use the terms “primary” and “secondary” to refer to these different types of sites; secondary stations could include both shrines, which could involve rock art and/or simple architecture, and alignments within or associated with buildings. The well-known, though not universally accepted, alignments at Pueblo Bonito and Casa Rinconada would fall into the secondary category, as would the “Sun Dagger” petroglyph site atop Fajada Butte. In this paper Munro and Malville focus on the primary stations, which they further divide into two categories depending on whether they could be used both to predict significant dates in the solar calendar and to observe them when they occurred, or just to observe the occurrence. For practical purposes the former type would be more useful.

Despite Chaco’s reputation for astronomy, it turns out that good locations for primary observation are pretty rare in the canyon. One key requirement for such a location is a “broken” horizon with obvious landmarks that can be used to track the sun’s (or moon’s) progress along the horizon, but from most great houses the horizon is actually pretty flat and unsuitable for observation. This is presumably due to the flat mesa tops to the north and south of the canyon itself. The number of possible locations for observation stations is therefore reduced to a few areas of the canyon where the horizon is more varied. Munro and Malville list five previously documented stations and add two more based on their own research. (A few more have since been identified.) They are briefly described below.

Fajada Butte with Green Vegetation

Piedra del Sol is a large rock near the current Chaco visitor center that has a wide variety of rock art as well as multiple astronomical alignments. Of particular interest is an apparent viewing station for summer solstice sunrise associated with a large spiral petroglyph on the northeast face of the rock. The horizon as viewed from this spot could allow for both anticipatory and confirmatory observations for the solstice. Even more intriguing, the station has a direct line of sight to the “Sun Dagger” site on Fajada Butte, suggesting that this may have been the location from which the observations were made that allowed the spiral petroglyph at that site to be placed in exactly the right position for the “dagger” of light to pierce it on the summer solstice.

There are multiple identified observation stations in the area of the Wijiji great house at the eastern end of the canyon. One site, 29SJ931, is near a pictograph site on a ledge near the great house and allows observation of the winter solstice. There are some features at the site that are similar to the sorts of features found at post-Chacoan observation sites in the Mesa Verde area, as well as evidence for later Navajo use, so it’s not clear that this site was actually used at all during the Chacoan era. Another site near Wijiji, 29SJ1655, has many Navajo petroglyphs nearby but does also have Chacoan rock art and a possible shrine, suggesting Chacoan as well as Navajo use. This site actually consists of three siting locations, allowing observation of both solstices as well as both equinoxes.

More firmly established as a Chacoan siting station is the Wijiji great house itself. From the northwest corner of the building a notch is visible on the horizon that serves as both an anticipatory and a confirmatory marker for the winter solstice: about two weeks before the solstice the sun rises at the left edge of the notch, and on the solstice itself it rises on the east edge. Since Wijiji was one of the latest great houses to be built in the canyon, it’s possible that it was sited at a location already used as a solstice observation station. As we shall see, it is not the only great house for which this appears to be the case.

Kin Kletso

Further west in the canyon, another late great house, Kin Kletso, shows a similar alignment to the winter solstice, with both anticipatory and confirmatory observations possible but in a different way. Here, looking from the southeast corner of the building toward a nearby cliff about two weeks ahead of the solstice (the same dates as the Wijiji anticipatory alignment) shows the sun rising at the base of the cliff. Over the course of the next few weeks, the same sunrise alignment is visible by gradually moving north along the east wall of the site, until on the solstice itself the alignment is visible from the northeast corner. As with Wijiji, it is possible that Kin Kletso was built at the site of an existing observation station, perhaps associated with the large boulder at the western end of the site. (I mentioned both the Wijiji and Kin Kletso observation alignments in my very first post on this site, as it happens.)

In addition to these previously identified observation stations, Munro and Malville describe two new ones based on their own recent research. Both of these are interesting partly because of what they imply about the date at which these sorts of observations began at Chaco.

29SJ2539 is in the general area of Wijiji, and also near the important Basketmaker III village of Shabik’eschee. The site itself includes a boulder with an alignment allowing for confirmatory observation of the winter solstice sunrise through a notch at the foot of a nearby cliff, along with a wide variety of artifacts and rock art indicating both Chacoan and Navajo use. An immediately adjacent site, 29SJ2538, includes a ledge overlooking the boulder that could have been used for storage but apparently wasn’t. Another nearby site is a small-house habitation that was excavated by Frank H. H. Roberts in 1926, now known as “Roberts Small House.” This site was apparently occupied over a long span of time, from Pueblo I through the post-Chacoan “Mesa Verdean” occupation of the canyon. It contained a large number of turkey bones, giving it the alternative name of “turkey house.” It also contained human remains, including some that have been argued to show evidence of cannibalism. Christy Turner, who initially made the cannibalism claim, identified the remains as dating to early Pueblo II, but Munro and Malville cite more recent research showing that they were actually from an earlier Pueblo I context. They also argue that there is no reason to associate the cannibalism evidence with the evidence for astronomical observation or related ritual practices, but without going into detail.

Looking West from Peñasco Blanco

Finally, Munro and Malville identify a possible observation point for winter solstice sunrise at Casa del Rio, an early great house just west of the canyon that seems to have been an important site in the Pueblo I period, with an exceptionally large trash midden suggesting possible feasting activity involving people beyond those living at the site. From this site (Munro and Malville don’t specify the exact viewing location) the solstice sunrise is aligned with West Point, the high point on the west side of West Mesa that contains a Chacoan shrine and has direct lines of sight to the Peñasco Blanco great house as well as to other shrines from which messages could be quickly sent throughout the canyon and beyond. This close association with the signaling network, in combination with the large amounts of trash (which seems to have been primarily domestic trash associated with food consumption, unlike the more complex contents of the later, more formal mounds associated with Chacoan great houses), implies that Casa del Rio may have been a location where people gathered for feasts and other ceremonies during the Pueblo I period, with at least some of the ceremonies tied to astronomical events such as the winter solstice (or the full moon nearest to it). In this scenario, inhabitants of Casa del Rio would have watched the sunrises over West Mesa to determine the dates of their festivals, then communicated those dates to others by signaling to the shrine on West Point, from which the signal could have been transmitted to many other places.

Speaking of signaling, Munro and Malville also discuss how it could have been done. Fires or smoke signals are possibilities, but another intriguing options would have been mirrors made of selenite, a mineral that can be polished to a high reflective sheen which is found in some natural outcrops in the Chaco area, including one near the observation site at 29SJ2539. Pieces of selenite were in fact found at 29SJ2539 itself, as well as at several other sites in the canyon.

Several interesting patterns emerge from the data compiled by Munro and Malville. First, the winter solstice sunrise appears to have been the most important astronomical event observed by the ancient Chacoans, at least judging from the viewing stations that have been identified so far. This is consistent with modern Pueblo ethnography, which similarly indicates the winter solstice as the most important event and sunrise observations as generally being more important than sunset ones.

Second, there is a strong association between possible viewing stations and so-called “Late Bonito” great houses, those built in the early AD 1100s toward the end of the period of Chacoan florescence, often in the so-called “McElmo” architectural style that is sometimes associated with influence from the north. The relatively standardized sizes and shapes of these great houses, as well as their short periods of construction, suggest an aggressive building program at this time that might have been associated with an attempt to reassert Chaco’s importance at a time when regional focus was starting to shift north to Aztec. Siting these buildings at locations already used as astronomical observation points, and designing them to incorporate aspects of such observation into the buildings themselves, may have been a way for Chacoan leaders to emphasize their esoteric knowledge and spiritual power at a time when it was being challenged.

Finally, and most interestingly from the perspective of the series of posts I’ve been doing lately, Munro and Malville provide tentative but intriguing evidence for astronomical observation points in and around Chaco Canyon beginning in the Pueblo I period. This would to my knowledge make this the earliest known evidence for detailed astronomical observation in the northern Southwest, and possibly in the Southwest as a whole (evidence for the Hohokam in southern Arizona is more ambiguous). That, in turn, provides further support for my theory that the rise of Chaco was enabled in part by the development of a new ideology in which astronomy played a major role.

In this regard it is interesting that one of the early centers for astronomical observation may have been Casa del Rio, which was one of the most important local centers during the late Pueblo I period when the great houses in the canyon proper were just starting to be built. As noted in my earlier post on Pueblo I in the Chaco area, it’s clear that at this time settlement was largely focused to the west of the canyon along the lower Chaco River, which may have been a conduit for migrants leaving the villages in the Dolores, Colorado area when they collapsed in the late ninth century. It may have been these migrants, bringing the lessons they had learned from their experiments in village life and adapting to a new and very different environment, who first began to pay careful attention to the sky, perhaps in an attempt to improve their prospects of survival in an area that is exceptionally arid even for the Southwest. If their initial adaptations were successful, as they appear to have been at least in some places, they may have begun to gain prestige and to attract additional migrants from various areas, who would have brought their own ideas and lessons learned. Astronomy may have been the development that united these people and allowed them to develop a new social order that would go on to underlie the spectacular achievements at Chaco that we see evidence of even today. And when that social order began to be challenged, for reasons that are still unclear, its leaders may have sought to revitalize it through a renewed emphasis on their astronomical knowledge in the form of the Late Bonito great houses.

Obviously this is all fairly speculative, but more and more evidence has been accumulating in recent years to focus and ground such speculation in solid data. Archaeoastronomical research has been a key part of this, and this article is an important contribution to the developing picture.

Munro AM, & Malville JM (2010). Calendrical Stations in Chaco Canyon Archaeoastronomy, 23, 91-106

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The Day the Sun Stands Still

Fajada Butte at Sunset

Today is the winter solstice.  This is an important time here in Chaco Canyon.  Judging from the practices of modern pueblos, where it’s no coincidence that many important dances and feasts take place around Christmas, New Year’s, and Epiphany, it’s likely that the solstice was a major event for their ancestors, the prehistoric Chacoans.  And, indeed, there is evidence encoded into both the buildings that the Chacoans built and the petroglyphs that they pecked onto the rock faces in and around the canyon that the winter solstice was important to them.  Although not all of the astronomical alignments proposed by the Solstice Project have been universally accepted even within the archaeoastronomical community, enough of them have checked out that the idea of at least some alignments is quite widespread and mainstream these days.

The most famous alignment is the “Sun Dagger” atop Fajada Butte, which is most commonly associated with the summer solstice but which also has (or, more accurately, had) a winter solstice alignment in which the main spiral is bracketed by two daggers of light, rather than being bisected by one dagger as on the summer solstice.

For all its fame, the Sun Dagger was actually not very precise.  It didn’t mark the exact day of the solstice, just the general time of year including it.  There are, however, many other alignments in the canyon that are much more precise.  One of these involves one of the mysterious “corner doorways” at the most famous of the Chacoan sites, Pueblo Bonito.

Corner Doorway at Pueblo Bonito

While most of these doorways, which connect rooms diagonal to each other, have not been found to line up with anything, there is one that serves as a very precise marker of the winter solstice.  At sunrise on the solstice, the rising sun casts a beam of light through the doorway.  One edge of this beam lies exactly along the vertical line of the corner opposite the doorway.  This alignment only occurs on the day of the solstice itself, although the beam begins to appear in the middle of October and gradually moves, day by day, until it reaches the corner on the solstice.  It then moves back, day by day, until it disappears.

While the precision of this alignment is certainly suggestive, there are some questionable aspects of it.  The most important is that the corner doorway connects two interior rooms.  The alignment works today because the outer wall that would otherwise block sunlight from reaching the corner doorway has fallen down.  If that wall were solid, as most of the walls of Pueblo Bonito are believed to have been, there would have been no way for the alignment to work at the time it was allegedly put into place.  It’s possible, then, that this particular alignment just happens to be a wildly improbable coincidence.

There are ways to save the alignment, however, if one is so inclined (as many are).  One option is to argue that the outer wall may not have gone up to the second story, where the corner doorway is.  While this could technically be true, since the surviving parts of the outer wall are all from the first story, the surrounding rooms all have second-story outer walls surviving in part, and one of those would likely have blocked the path of the sunlight even if there were no second-story wall in the room right next to the corner doorway.  The other, more plausible, argument is that there was a second corner doorway, aligned with the surviving one, in the outer wall.  It’s true that corner doorways are exceedingly rare, and that none of the known examples is in an exterior wall.  Furthermore, there are very few exterior doorways in Pueblo Bonito at all.  Very little of the outer wall above the first floor has survived in most of the building, however, so it remains entirely possible, though unproven and unprovable, that there was a second doorway to facilitate the alignment.

If the corner doorway alignment at Pueblo Bonito is in fact genuine, one very interesting aspect of it is that the beam of light begins to come through a fixed number of days before the solstice and moves a little bit each day until it reaches its crucial alignment on the solstice itself.  This would make it useful as a device for marking time until the solstice, which would have been a very important consideration if the solstice itself was the occasion of important events that required significant advance planning.

There are some other solstice markers, less problematic than the corner doorway, which seem to have exactly this function.  From a vantage point at the northeast corner of Kin Kletso, a smaller, later site about half a mile to the west of Pueblo Bonito, the solar disk rises on the winter solstice right in a notch along the horizon.

Kin Kletso

There are alignments like this all over the canyon, tied to key features on the complicated horizon line that allow easy tracking of the sun’s movement through the year.  What makes Kin Kletso notable, however, is that from a vantage point at the southeastern corner the sun rises in the same notch two weeks before the solstice, and if one were to move gradually northward along the wall every day for those two weeks the sun would continue to rise in that same notch.  This would be a very effective way to count down the time until the solstice for planning purposes.

A notch seems just a little arbitrary, though.  There are all sorts of horizon features, and the number of possible viewing locations is literally infinite.  This is a common and partly unavoidable problem with archaeoastronomy in general: if you draw enough lines, something is going to line up.  Luckily, in the case of Chaco there are some additional reasons to trust in the likely accuracy of at least some of the proposed alignments.  Probably the most important of these is the fact that the modern pueblos have held onto a great deal of their traditional knowledge, and astronomical observation is a documented part of that.  Some of the pueblos, notably Hopi and Zuni, have sunwatchers to this day, and while the details of their practices are generally considered sacred knowledge not to be divulged to outsiders, enough has become known in various ways to demonstrate a strong continuity with ancient evidence.

Another line of evidence has to do with the specific shapes of some of the horizon features.  A notch isn’t always just a notch.  One good example of this is at Wijiji, a site roughly contemporaneous with Kin Kletso but at the other end of the canyon.

Wijiji

From the northwest corner of Wijiji, looking across the plaza to the southeast, the sun rises on the winter solstice in a notch.  The right side of this notch, from this perspective, happens to have the exact same inclination as the path of the sun, so as the sun rises, on this day and only this day, it appears to run along the side of the notch before continuing up into the sky to continue its journey.  Definitive evidence for the reality of alignments?  Certainly not.  Suggestive of it?  Certainly.  An inspiring, thought-provoking phenomenon?  No question at all.

While the extent and purpose of astronomical alignments will continue to be debated for quite some time, there’s no escaping the sense that the sky is an ever-present and awe-inspiring feature of Chaco Canyon.  The sunsets are amazing.

Winter Solstice Sunset

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