Archive for the ‘Archaeoacoustics’ Category


Salmon Ruins Sign

One of the most interesting chapters in Astronomy and Ceremony in the Prehistoric Southwest: Revisited reports on archaeoastronomical research at Salmon Pueblo (also known as Salmon Ruins), a large Chacoan “outlier” great house near modern Bloomfield, New Mexico. The paper is by Brooks Marshall and Larry Baker of the San Juan County Museum Association, which manages the site, and it argues that one particular room at Salmon was likely used as an observation station for both solar and lunar events.

The room, known as Room 82, is in the southeast corner of the central room block on the north side of the plaza, just southeast of the elevated “tower kiva” in the center of the block. When it was excavated in the 1970s, the excavators found that it had several unusual features that suggested it was used for specialized non-domestic purposes, though it was not clear to them at the time what those might be. In addition to the commonly found hearths, milling bins, and T-shaped doorways, there was an unusual opening in the east wall which Marshall and Baker call a “window” (unfortunately they don’t explain why they use this term, which is generally not used in describing Chacoan architecture), an adobe platform in the northwest corner that had two shallow pits at its north end, and a dividing wall in between of uncertain original height. The platform and wall were destroyed in the course of excavation, while the window has deteriorated a bit over time but is still there.

The unusual nature of these features and their east-west alignment made Marshall and Baker suspect an astronomical role, so in 2008 they created a replica of the adobe platform out of plywood and positioned it where they calculated it would be hit by light through the window at equivalent times to the original, taking into consideration the higher floor level due to backfilling of the room. In 2009, a stabilization project removed the backfill and allowed them to place the replica in the original location of the platform to verify their results. Further testing in 2010 and 2011 involved simulating the original size and shape of the window opening. Throughout these tests they placed two rocks on the platform to simulate the two pits at the north end of the original, known as Features 71 and 72.


Central Roomblock at Salmon Ruin

Their results were striking. They found that the northernmost pit, Feature 72, was lit by sunlight coming through the window only on the summer solstice, and when the original window opening was simulated the light was quite narrowly focused on this feature. Feature 71, despite being only a few centimeters away, was never lit up by the sun at all. It was, however, lit by moonlight during the major lunar standstill, when the moon rises at its most extreme position relative to the sun for a few years. It’s long been known that the first major period of construction at Salmon in AD 1089 and 1090 corresponds to the lead-up to a major lunar standstill, and indeed Marshall and Baker’s calculations showed that it was in these years that moonlight would have first illuminated the features at the north end of the platform. By the standstill itself, which lasted from AD 1093 to 1095, moonlight would have hit about three quarters of the platform. Marshall and Baker propose that the south end, which is never nit by moonlight, may have served as an observation point where someone could sit and observe the moonlight move across the platform over time, possibly allowing the prediction of the standstill.

Obviously the wall in between the window and the platform adds a complication to all this, as it would have blocked at least some light from coming through. There’s no way to tell how high it initially was, so Marshall and Baker ran some calculations based on different heights to see how they effected the illumination patterns they documented. They found that at a certain height the wall would have prevented the beam of light coming through the window from moving beyond the platform onto the floor, which may have been intentional. At higher heights it would have blocked the beam entirely, but the base of the wall was fairly thin and probably couldn’t have supported a full-height wall.


Excavated Rooms at Salmon Ruin

This is exciting research for several reasons. It’s always interesting to see a careful study of architectural alignments to celestial phenomena that takes into consideration excavation history and possible confounding factors. It’s particularly interesting that this study seems to have shown strong evidence for alignments even taking those other factors into consideration. The solstice alignment seems like the best established to me, which is unsurprising since solstice alignments in general are the best documented phenomena in ancient Pueblo archaeoastronomy. What I find most intriguing, however, is the possible lunar alignment and its relation to the construction dates at Salmon, since despite a lot of talk about lunar alignments at Chacoan sites very few have been securely documented, and unlike solar alignments there is no support for them in modern Pueblo ethnography. If this lunar alignment really does hold up, it helps strengthen the argument that the Chacoans really did observe and care about these subtle lunar cycles.

The strongest evidence so far for Chacoan observance of lunar standstill cycles comes from Chimney Rock Pueblo, further north in Colorado. The evidence here is quite strong indeed, as the full moon rises between twin spires of rock as seen from the great house only during the major lunar standstill, and this accounts for the otherwise very puzzling location of the great house atop a high, steep mesa. There is also some evidence from the dates of construction at Chimney Rock that some building periods were related to specific lunar cycles. The lack of support from other Chacoan sites, however, has made the seemingly solid evidence fr,om Chimney Rock hard to integrate into the picture as a whole. If people at Salmon, which is fairly close to Chimney Rock and is connected to it by an easy travel corridor along the San Juan River, were also marking the lunar standstill cycle, the picture begins to fill out a bit.

That said, this research is still fairly preliminary and I wouldn’t go as far as to say that the lunar alignment proposed here has been definitely established. More research is certainly necessary to confirm and interpret the patterns documented here. It is certainly suggestive, however, and very interesting.


Backfilled Rooms at Salmon Ruin


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Chaco Amphitheater

There’s a spot near the west end of the Pueblo Bonito parking lot, close to the spot where guided tours begin, where you can yell something in the direction of the canyon wall and hear a very clear echo back.  Some of the tour guides at Chaco regularly demonstrate this impressive effect when beginning their tours, and it’s certainly an interesting way to capture people’s attention.  I never did it myself; I’m generally averse to this sort of thing because I’m never confident that I’ll get it quite right, and it would be very awkward if I tried it and it didn’t work.  (There’s a similar effect in Statuary Hall in the US Capitol which I never demonstrated when I gave tours there either.)  This is kind of silly, though, and says more about me than about the echo.  In general I think highlighting this kind of acoustic effect is a good way to show just how special Chaco is, and while this particular echo is in a very accessible location there are many other places in the canyon with similar characteristics.  There are several places in and around Pueblo Bonito where you can hear with crystal-clear precision everything people say up on the Threatening Rock overlook, and there are some spots where you can even hear things clear across the canyon.

Secret Passage into Casa Rinconada

These effects have been known to the park’s interpretive staff for a long time, but until recently they’ve received very little attention from scholars.  In the past few years, however, the growing field of archaeoacoustics has begun to look rigorously at echoes and other acoustic phenomena in the canyon with an eye to understanding what role they may have played in Chaco’s past.  Rich Loose, a former archaeologist and old Chaco hand, has been at the forefront of this research, in collaboration with our old friends John Stein and Taft Blackhorse.  Rich recently sent me a couple of articles of his that have recently been published on this issue, along with a paper by John and Taft that I don’t think has been published anywhere.  The most important of these articles, I think, is one in which Rich describes in detail the research the team has done at the so-called “Chaco amphitheater” between Pueblo Bonito and Chetro Ketl.  Using sophisticated recording equipment and acoustic analysis software, they made a series of recordings of different sounds produced in various locations in and around the amphitheater and determined many of its important acoustic properties.  They also examined the cliff face in this area and concluded that there was considerable evidence that it had been deliberately sculpted, perhaps to improve its acoustic properties or for other purposes related to its use as a performance venue.  There is some evidence that there may have been a masonry wall along at least part of the sculpted area which could have created a “backstage” for performers, which Rich compares to the “secret passage” at Casa Rinconada.  There are also three large holes in the cliff face which appear to be natural but may have been enhanced as well.  One of these is large enough to fit a person and leads to a small cave that can apparently fit multiple people (though presumably in very close quarters).  Again, this has interesting implications for possible stagecraft.

Pueblo Alto and New Alto from Tsin Kletzin

One of the most interesting discoveries in Rich’s paper involves a small hill on the other side of the canyon, near Casa Rinconada, which he concludes was almost certainly deliberately constructed artificially for some purpose related to the amphitheater.  This hill, which is quite prominent and which I have often wondered about, apparently doesn’t show any sign of covering up a small-house site like the ones surrounding it, but neither does it appear to be natural.  It is, however, located almost exactly on the line along which sound from the amphitheater focuses, which also seems to coincide almost exactly with the north-south line between Tsin Kletzin and Pueblo Alto.  Sounds played from the hill could be clearly heard in the amphitheater, although their source could not easily be ascertained from there, and even speech from the hill could be heard in a somewhat garbled manner.

Canyon Wall from Pueblo del Arroyo

As with archaeoastronomy, archaeoacoustics suffers from the persistent problem that there’s no way to know for sure if the patterns it discovers are real or due simply to coincidence.  Rich is quite open in acknowledging this shortcoming in his articles.  In the absence of any means to verify results completely, a compelling combination of separate types of evidence is the best way to support an argument that the acoustic properties of a place are not accidental but reflect conscious decisions on the part of ancient people.  In the case of the Chaco amphitheater, I think Rich’s results clearly meet this standard.  Again as with archaeoastronomy, it’s hard to say what the specific implications of all this are for understanding prehistoric behavior, but in this case the acoustic evidence seems to shed at least some tentative light on several mysteries about Chaco.

Huerfano Mesa from New Alto

One of these is the nagging question of why Chaco was chosen in the first place as the location for such a grandiose center, given that it has no apparent natural resources and is in a particularly harsh and inhospitable location even by local standards.  The acoustic properties of the canyon walls, however, which as I noted above are not limited to the phenomena at the amphitheater specifically, provide one possible answer.  The main way in which Chaco does differ from the surrounding San Juan Basin is that it is, of course, a canyon, and has a long stretch of exposed sandstone cliffs with acoustic effects that can’t be found in many other places nearby.  This doesn’t necessarily explain its advantages in a larger geographic context, of course, and there are many other places just a bit further away with similar sorts of cliffs, but it does potentially shed some light on the question of what leverage the Chacoans would have had over other people in the area that they could use to gain their important position in the region.  People often gesture vaguely to “spiritual authority” or something similar in trying to explain this, but the acoustics provide an explanation for how a reputation for spiritual power could arise in the first place.  The position of the amphitheater at the center of the canyon, at the intersection of many alignments between buildings, certainly suggests that it was an important focal point for the area, and the acoustic characteristics are very suggestive.

Looking East from the Pueblo Alto Trail

Since this research involves John Stein and Taft Blackhorse, of course, Navajo oral traditions also enter into the story.  Specifically, the unpublished paper by John and Taft talks about a connection between the amphitheater and a ritual involving the use of the hallucinogenic datura plant, as well as a connection to the Great Gambler (specifically that the Gambler came to Chaco to take advantage of the powers associated with the amphitheater).  Indeed, they even say that the amphitheater is still used by “Navajo ceremonial practitioners,” which Rich incorporates into his articles as a key piece of evidence backing up his acoustic studies.  I’m a little dubious about a lot of this, and I intend to look into it further, but I do think oral traditions are an important place to look for an independent line of evidence to serve as a check on conclusions derived from archaeoacoustic (and archaeoastronomical) research.

Shell and Jet Display at Chaco Museum

Another issue this acoustic research sheds light on is the remarkable number of musical instruments, many quite elaborate, found in excavations at Chaco.  Almost all of these were found at Pueblo Bonito; the flutes in Room 33 are probably the best known, but I want to focus here on the conch shells apparently used as trumpets, which were also quite numerous and found in many rooms at Bonito.  Rich mentions these in his articles as well, although he doesn’t go into great detail about them.  He does, however, note that a conch shell trumpet was one of the sound sources he used in his archaeoacoustic research, and adds this interesting statement:

I found the shell trumpets to be one of the easiest ways to produce a loud stimulus for an echo. They are simple, easily portable, don’t require batteries, and are nearly foolproof once you master the technique of blowing one.

As luck would have it, Barbara Mills and T. J. Ferguson have recently published an important article on shell trumpets in the prehistoric Southwest in which they record all the places they have been found and try to see what conclusions about prehistoric ritual and ideology can be drawn from the distribution of trumpets through time and space.  They conclude that there are at least two separate ideological systems associated with shell trumpets: one having to do with the plumed serpent and associated with rain and agricultural fertility, and another having to do with warfare and healing (these might be two separate traditions, in which case there would be a total of three traditions).  Temporally, they find that the plumed serpent tradition, which is quite strong at Hopi and Zuni today, appears rather suddenly in the early fourteenth century, a time of considerable population movement and cultural change, and may have something to do with influence from the major center at Casas Grandes in Chihuahua as well as with migration of large numbers of people from the southern Southwest into the Pueblo region.  During this period conch shells are found primarily at Casas Grandes and in a large area of east-central Arizona along the Mogollon Rim, as well as in the Hohokam region of southern Arizona and as far east as Pecos.

Kiva A at Pueblo Bonito from Above

There is basically no evidence for plumed serpent iconography earlier than AD 1300, although there are conch shells.  Their distribution is much more limited, however, being confined essentially to the Hohokam region and Chaco, although there is one isolated example from the Mimbres area of southwestern New Mexico.  The geographic isolation of Chaco is striking on their map of sites where conchs have been found; there don’t seem to be any examples from any other sites on the Colorado Plateau during this period, despite the large population of this area and the presence of many strongly Chacoan-oriented or -influenced regional centers.  Apparently there were no shell trumpets even at Aztec, which is in general pretty similar to Chaco in the numbers and types of valuable artifacts found.  There were a bunch of them at Chaco, however, at least 17 overall, and all except two of them came from Pueblo Bonito specifically.  Within Bonito they were generally found in significant locations such as rooms containing other rare artifacts and a wall niche in Kiva R, rather than in trash deposits, which suggests that they were particularly important items.  One was found in Room 33, and four were found in Room 38, which also contained many rare items of apparent ritual significance as well as macaws.  Others were found in Kiva A (the great kiva in the east plaza) and Room 6 (one of the earliest rooms in Old Bonito).  Clearly, then, conch trumpets seem to have been associated very closely not just with the Chacoan system or Chaco Canyon in general but with Pueblo Bonito specifically.  And Pueblo Bonito, of course, is right next to the amphitheater.  The combination of the impressive acoustics of the amphitheater with the exotic sound of the conch shell would likely have been pretty powerful, perhaps in more ways than one.

Intact Roof Beams in Room 6, Pueblo Bonito

So what light does this combination shed on the Chacoan system overall?  Well,  it’s hard to say for sure.  Mills and Ferguson make a strong case that the Chaco and early Hohokam conchs are associated with the warfare/healing complex rather than the plumed serpent one.  Evidence for this complex comes mainly from Zuni, where there are many stories about the use of a “Big Shell” that was used to magically defeat the enemies of the Zunis.  There is also an association between this shell and witchcraft, both in fighting it and in possibly causing it.

Shell Display at Visitor Center Museum

The (non-witchcraft-related) healing part of the complex comes from one of the medicine societies, best known at Zuni but apparently also present at Hopi and Zia, and historically at Laguna.  This society is apparently named for a “spiral shell,” and its rituals include shells, but otherwise it’s not clear how much it has to do with conch shells or trumpets specifically as opposed to shells more generally.  The songs of the society at Zuni are said to be in the O’odham language of southern Arizona, and its origin story mentions a series of long migrations.  To me this combination suggests a Hohokam origin about as clearly as is conceivable, and it’s possible that at least some of the Hohokam conchs, particularly the small ones that may have been used as standards on staffs rather than as trumpets, may have been associated with a precursor of this society.  As I said, though, I’m not totally convinced that conchs specifically have anything to do with this society.  Shells of all kinds were a very big deal among the Hohokam.

Chaco Amphitheater in the Snow

So, given all that, it seems likely that if any conch-related ritual complex in the modern Pueblos is related to the conchs at Pueblo Bonito it’s the Zuni Big Shell, associated with warfare and witchcraft.  This is certainly intriguing, especially given the odd and ambiguous evidence about Chaco’s connections to warfare, although I think it’s ultimately inconclusive.  As Mills and Ferguson point out, it’s entirely possible that some of these prehistoric complexes have no modern equivalents at all.  Indeed, given the massive series of cultural changes and migrations separating Chaco from the modern Pueblos, it would hardly be surprising that the ritual traditions closely associated with Chaco specifically would have been lost or abandoned in favor of newer (or perhaps older) rituals considered more suited to the changing times.  It’s noteworthy that there don’t seem to be any modern (Pueblo) practices involving a combination of conch trumpets and cliff faces with special acoustic properties, given the strong circumstantial evidence that the two were connected at Chaco.  Whether or not any modern practices involving shell trumpets can be traced back to Chaco, however, the evidence for their importance at Chaco itself at its height is evocative and provides a hint of what Chaco may have been like for the Chacoans, even if what we hear today is only a faint echo of what they heard then.
Mills, B., & Ferguson, T. (2008). Animate Objects: Shell Trumpets and Ritual Networks in the Greater Southwest Journal of Archaeological Method and Theory, 15 (4), 338-361 DOI: 10.1007/s10816-008-9057-5

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