Archive for the ‘Natural Environment’ Category


Tijeras Pueblo Overlook

I’ve written some posts before on the interesting recent research being done on the analysis of DNA and stable isotopes to study the genetics and subsistence of the turkeys of the prehistoric Southwest. A recent short paper adds an interesting dimension to this research, by looking at these issues in a sample of turkey remains from a site on the fringe of the Pueblo world, near its interface with the Plains.

The site in question is Tijeras Pueblo, in the Sandia Mountains just east of Albuquerque, New Mexico. The researchers were interested primarily in looking at the stable isotope chemistry of these turkeys to determine whether they primarily ate maize or wild plants, to try to determine how they were raised. In addition, they looked at the DNA of a subset of them to see if they belonging to a previously identified genetic line of domestic turkeys identified in the prehistoric Southwest, or to a separate line associated with modern wild turkeys. In theory, one might expect that turkeys that ate maize belonged to the domesticated line and ones that ate wild foods belonged to the wild one.

In fact, however, what they found was more complicated and interesting. The turkeys fell into two groups which were quite distinct in their chemistry: one that seemed to have eaten maize and another one that seemed to have eaten wild plants. However, the latter group did not have chemistry quite the same as that of the modern wild turkey specimens they compared it to, and was instead somewhat “intermediate” between the maize-fed ones and the wild ones. This suggested to the authors that these turkeys may have been free-ranged, eating a mix wild plants, some maize, and perhaps also insects, and that some of this free ranging may have been in the cornfields for pest control. Similar husbandry practices are documented in the modern Pueblos but had not previously been identified prehistorically.

Even more interesting, however, was the genetic data. Despite the sharp distinction between subsistence strategies implied by the chemical evidence, almost all of the tested specimens belonged to the domesticated ancient Southwestern lineage, and not the wild one. This suggests that the difference in husbandry practices did not correlate to separate origins of the turkeys, but to something different.

Comparisons to specimens from other areas shed some light on possible reasons for this pattern. The researchers compared these turkeys to some from the Albuquerque area, from the Gallina area, and from Arroyo Hondo Pueblo to the north in the Northern Rio Grande area. Since Tijeras Pueblo is at a relatively high elevation where maize agriculture is somewhat marginal, it might be expected that this environment explains part of the difference in turkey husbandry. And when compared with the nearby but much lower Albuquerque samples and the more distant but comparably high-elevation Gallina ones, there is some evidence for this: the Albuquerque samples grouped with the maize-fed Tijeras ones, and most of the Gallina samples grouped with the free-range Tijeras ones. However, the Arroyo Hondo samples, though also high-elevation, showed a much more maize-based pattern, so there is something more than environmental difference going on here.

The authors suggest that the position of Tijeras Pueblo on the eastern fringe of the Pueblo world, at its interface with the very different cultural world of the Plains, may account for the diversity of the turkey husbandry types shown in their data. Conversely, Arroyo Hondo was further within the Pueblo world, while the Gallina region was culturally distinct in ways that are still poorly understood. The authors recognize, however, that further research will be necessary to flesh out the context of these results. In any case, this is a very interesting paper that adds another little bit to our knowledge of the past.

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Macaw Feathers and Copper Bell on Display at Chaco Visitor Center Museum

One of the most exciting recent developments in the study of Chaco Canyon is the increasing use of scientific analysis of artifacts and other material remains to test and challenge previous theories based more narrowly on traditional archaeology. This includes the use of radiocarbon dating, which is widely used as a basis for developing chronologies in most other parts of the world but has been underused in the Southwest due to the availability of tree-ring dating for chronology building. Particularly with the development of accelerator mass spectrometry (AMS) radiocarbon dating, which requires vastly less material than earlier methods, however, it is now possible to gain direct dates on a very wide variety of materials, including many artifact types as well as plants and human and animal bones. This allows an independent check on dating of material by association with tree-ring dated architecture and pottery, which has been the traditional approach. The increasing use of AMS on the museum collections excavated decades ago from Pueblo Bonito, in particular, is starting to lead to some unexpected and surprising conclusions. This work is largely being done by archaeologists associated with the University of Virginia led by Steve Plog, in collaboration with colleagues at many other institutions.

One recent paper, about a year old now, reported some surprising results from the dating of the bones of one of the most distinctive species found at Chaco: scarlet macaws. These birds are not native to anywhere near the Southwest, and they must have been brought up from very far south in Mexico. They are disproportionately found at only a few sites in the Southwest, one of which is Pueblo Bonito. Traditionally it has been thought that the importation of macaws was associated with the “florescence” of Chaco, the roughly 100-year period starting around AD 1040 when most of the monumental great houses in the canyon were built and Chacoan influence is seen over a very large part of the northern Southwest. For this study, the researchers dated 14 macaws from Pueblo Bonito: 11 from Room 38, which had the highest concentration of macaw remains at the site, two from Room 78, and one from Room 71. Both of these latter rooms are in fairly close proximity to Room 38 within the site. They also dated four macaws from Mimbres sites in southwestern New Mexico, another area with a relatively high concentration of these birds that lies between Chaco and Mexico and thus could played a role in their procurement, and two from Grand Gulch in Utah, which is on the far fringes of the ancient Pueblo world and yet has produced a few macaw specimens.

The results were surprising, and they challenge the traditional association of macaws with the Chacoan florescence. Six of the Chaco birds dated to between AD 885 and 990 (all dates given here are at 95% probability), well before the florescence and a time when Chaco would have been much less impressive architecturally. This is, however, a time when population in the canyon was increasing rapidly through immigration from various areas that were affected by the big changes at the end of the Pueblo I period, as we have seen in my recent series of posts on Pueblo I. The authors of this paper don’t mention this population movement specifically, but they do suggest that this indicates that the later period of monumental construction and other signs of sociopolitical complexity was the result of a long period of developing complexity, which fits the demographic evidence pretty well.


Room 38, Pueblo Bonito

Six other birds date between AD 970 and 1035, which would put them shortly before or possibly at the very beginning of the florescence and building boom. This suggests that trade relations with the far south continued beyond the initial period when macaws were introduced to the canyon. The final two date between AD 1015 and 1155, which suggests they probably were procured sometime during (or even shortly after) the period of florescence. Overall the dates suggest that macaws were procured throughout most of the period of Chaco’s rise from the period when Chaco was first rising to regional preeminence in the ninth and tenth centuries until its loss of preeminence (I think “collapse” is too strong a term for this still poorly understood phenomenon) in the twelfth.

One thing you may have noticed about those date ranges, however, is that they all overlap. Given the statistical uncertainty of radiocarbon dates, this means that it’s possible that these dates indicate a continuous process of importation of macaws from Mesoamerica. (There is no evidence for breeding of macaws at Chaco, unlike at the later site of Casas Grandes in northern Chihuahua.) The clustering of sets of dates, however, suggests on the contrary that importation was sporadic, with possibly just three individual procurements of multiple birds at a time. And additional complication is that the shape of the radiocarbon calibration curve differs at different times through this sequence, which can lead to certain time periods being over- or under-represented in series of dates. To test these hypotheses, the authors did some simulation of random dates throughout the period in question and compared the resulting distributions with the actual distribution of macaw dates. The results were that the early cluster of dates did conform to what might be expected from the effects of the shape of the curve, the middle cluster had more dates than would be expected and the late cluster fewer. This suggests that while it is possible that procurement of macaws was a continuous process, it does appear that a larger number of birds were imported in the late tenth and early eleventh centuries than earlier or later. Of course, this is a small sample, and these apparent patterns may change with more data.

As for the non-Chaco macaws, one of the Mimbres ones dated to AD 895 to 1020, straddling the first two clusters of dates at Chaco, while the other three all dated from around AD 1015 to 1155, as did the two Grand Gulch specimens. This suggests that macaws were present earlier at Chaco than in areas to either the north or south, which further suggests that at least initial importation of macaws to Chaco didn’t necessarily depend on Mimbres middlemen. Macaws have also been found at Hohokam sites in southern Arizona that appear to be in earlier contexts than the ones at Chaco, but none of these have yet been directly dated.


Room 33, Pueblo Bonito

While it may appear initially surprising, the early dates for macaws at Chaco do actually fit with increasing evidence from other sources suggesting that the rise of Chaco and its social and economic power significantly predated its “florescence” as seen in monumental architecture. This includes a study from a few years ago, from the same group of Virginia researchers, that dated human remains from Room 33 in Pueblo Bonito, including the two burials that were associated with enormous numbers of valuable grave goods, and found those two burials long predated the Chacoan florescence and may in fact have been contemporary with the earliest construction at the great house in the mid-ninth century or even earlier. (That paper really deserves a post of its own, which I keep meaning to write, but this brief summary will have to do for now.)

Taken in conjunction with the evidence for regional population movement in late Pueblo I, this study provides more support for the idea that the influx of populations into the canyon in the late ninth century, some bringing ideas developed in the earlier short-lived villages to the north in Colorado, set the stage for the development of new ideas about social organization and hierarchy which may have led to new ideologies and the importation of both goods and ideas from areas far away. The fact that macaws would have to have come from the south, where the archaeology of areas immediately adjacent to the Chacoan region is much more poorly known than that of comparable areas to the north, points to the importance of developing a better understanding of those areas. We still know very little about the exact routes of trade connections to the south, even as the importance of those connections becomes increasingly apparent.
Watson, A., Plog, S., Culleton, B., Gilman, P., LeBlanc, S., Whiteley, P., Claramunt, S., & Kennett, D. (2015). Early procurement of scarlet macaws and the emergence of social complexity in Chaco Canyon, NM Proceedings of the National Academy of Sciences, 112 (27), 8238-8243 DOI: 10.1073/pnas.1509825112

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McPhee Reservoir, Dolores, Colorado

McPhee Reservoir, Dolores, Colorado

The first of the shorter, more analytical chapters in Crucible of Pueblos that follow the regional summaries is one by James Potter looking at faunal remains, which in this context basically means animal bones. (I guess this is sort of appropriate for a Halloween post, although animal bones aren’t really as spooky as human ones.) This chapter is basically a series of statistical comparisons of faunal assemblages from different Pueblo I sites, focusing particularly on the large, well-document collections from the Dolores and Animas-La Plata Projects, but also including a few others. Given the focus on these collections, the geographical range of these comparisons is limited to the Central and Eastern Mesa Verde regions. Nevertheless, Potter finds some striking differences between different sites that have interesting implications for understanding their inhabitants’ lives.

The first comparisons are of different villages within the Dolores area. Potter uses two widely used calculations, known as the artiodactyl index and lagomorph index, to compare McPhee Village on the west side of the Dolores River to Grass Mesa Village on the east side. The artiodactyl index is a measure of how common large game animals, such as deer and elk, are within the overall assemblage, and is calculated by taking the number of artiodactyl specimens in the assemblage and dividing it by the number of artiodactyl specimens plus lagomorph (rabbit and hare) specimens. The lagomorph index compares the number of specimens of the two most common lagomorph species, cottontail rabbits and jackrabbits, and is calculated as the number of cottontail specimens divided by the combined number of cottontail and jackrabbit specimens. This is an important measure because cottontails and jackrabbits favor different habitats and have different behavior which can shed light on human land use and hunting practices: jackrabbits prefer open spaces such as those created by clearing land for agriculture, and as a result can often be caught within gardens, while cottontails prefer more sheltered brushy environments. Jackrabbits also run to escape predation while cottontails hide, which makes the former more vulnerable to the kind of communal hunting known to have been practiced by Pueblo peoples in more recent times.

In the case of McPhee and Grass Mesa Villages both indices show little to no difference between the two; indeed they are nearly identical. This suggests that there weren’t major differences between the two communities in land clearing, communal hunting of lagomorphs, or hunting of artiodactyls. This is maybe not surprising, as the two villages are only a few miles apart and in similar ecological settings.

Where they do differ, however, is in another comparison, in this case of the prevalence and diversity of bird remains. McPhee Village has many more bird remains, representing more than twice as many species, than Grass Mesa, despite the overall sample sizes being similar. Furthermore, the avian bones are concentrated within McPhee Village at one particular residential site, known as McPhee Pueblo. This is one of the largest residences in the community and has features that have been interpret as reflecting ritual activity at a level higher than the individual residential group inhabiting the site. This site is considered likely to be a prototype of the “great houses” associated with the later cultural phenomenon centered on Chaco Canyon, where many of the inhabitants of the Dolores area are thought to have gone after the demise of the Pueblo I villages there in the late ninth century AD. The greater number of bird species, and the large number of specimens, at McPhee Pueblo reinforces other indications of the special role this site played in the community. Birds have often been associated with ritual among the Pueblos, with the macaws at Chaco being only one of the most spectacular examples. The fact that there is no similar site at Grass Mesa, and that bird remains are much rarer there overall, suggests significant differences in ritual organization at the two villages despite their proximity, which fits with other evidence suggesting they were settled by people from different cultural backgrounds.

The second major set of comparisons Potter makes addresses change over time, again within the Dolores area. He compares the artiodactyl and lagomorph indices of McPhee Village and the nearby but earlier community of dispersed hamlets known as Sagehen Flats. In this case, the Sagehen Flats sites had much lower artiodactyl indices, which suggests to Potter that this community had more difficultly organizing hunting parties to capture these large animals than the later, larger, and more aggregated community at McPhee. Indeed, it has been suggested that one reason for the formation of the large Pueblo I villages was the opportunity that larger communities provided for more effective hunting of large animals, especially in high-elevation areas close to large populations of artiodactyls.

Sagehen Flats also had a higher lagomorph index value, indicating more cottontails relative to jackrabbits, and suggesting that aggregation at McPhee also included more clearing of land for agriculture, creating the open spaces preferred by jackrabbits. It is also likely that larger communities were more effective at communal hunting, which as noted above would have been easier with jackrabbits. It’s not really surprising that larger communities would have cleared more land for agriculture and conducting larger communal hunts, but this evidence does provide another reason to think that.

Bird remains, on the other hand, were present in very similar proportions at both Sagehen Flats and McPhee, with both much higher than Grass Mesa. This likely results in part from the location of Sagehen Flats near marshes with lots of good habitat for waterfowl, but it’s also noteworthy that the bird remains there, as at McPhee, were heavily concentrated in one habitation site. This site, unlike McPhee Pueblo, doesn’t show other signs of having been exceptionally important compared to others, but it is highly intriguing that there were so many birds there, and it suggests that the pattern of unequal ritual influence seen at McPhee, and later at Chaco, goes back even further, at least in this area.

Durango, Colorado

Durango, Colorado

Next, Potter does a broad comparison of several different site areas, this time treating the Dolores sites as a whole and comparing them to the nearby hamlet of Duckfoot as well as the site clusters of Ridges Basin and Blue Mesa to the east near the modern city of Durango, as well as sites in the Fruitland area to the south near the modern Navajo Reservoir. Starting with the artiodactyl and lagomorph indices, Potter finds high artiodactyl index values at Dolores and Ridges Basin, with much lower ones at Duckfoot and Fruitland. The factors mentioned earlier leading to more effective artiodactyl hunting in larger villages are probably one factor here, with another being elevation, with the higher sites having more artiodactyls than lower ones.

The lagomorph index is highest at Duckfoot and Blue Mesa and lower at Dolores and Ridges Basin, again echoing the pattern seen before where larger villages show evidence for more land clearing and communal hunting compared to smaller, more dispersed sites.

Turning to birds, Potter finds the highest numbers in Ridges Basin, with significantly smaller numbers at Dolores and Duckfoot. (Keep in mind that all of the Dolores sites are lumped together here.) This is likely due in part to the marshy environment of parts of Ridges Basin, but it is also due to much more extensive use of turkeys in Ridges Basin than elsewhere.

Following these rather simple comparisons, Potter does a correspondence analysis of all of the areas comparing categories of animal remains: birds, wild carnivorous mammals, domesticated dogs, lagomorphs, and artiodactyls. This analysis shows that the areas have very distinct associations with particular types of animals. Blue Mesa, Fruitland, and Duckfoot are associated with lagomorphs, Dolores with artiodactyls, and Ridges Basin with both birds and dogs. Potter notes that while Dolores and Ridges Basin have very similar artiodactyl indices, as this analysis suggests, they have very different overall percentages of artiodactyls. The index is thrown off because it uses lagomorph numbers to standardize the artiodactyl numbers, which is problematic in cases like this because the number of lagomorphs also differs a lot between the two areas, with a lot fewer of them at Ridges Basin than at Dolores.

Next, Potter does a detailed analysis of the Ridges Basin community, comparing categories of remains among different site clusters within the basin. He uses a more detailed set of a categories here than in the previous analysis: mammalian carnivores, birds of prey, waterfowl, dogs, turkeys, game birds, artiodactyls, and lagomorphs. The different site clusters show interesting differences in the proportions of these, with the marshy eastern cluster having higher numbers of waterfowl and turkeys. As mentioned above, turkeys are more common throughout Ridges Basin than in other Pueblo I communities, but there are differences in both numbers and context within the basin. The turkeys in the eastern sites are mostly burials, part of a widespread Pueblo practice of burying domestic animals that likely has ritual significance. In some site clusters, however, there is evidence for processing of turkey remains suggested they were used as food. In the north-central cluster there is one pit structure that seems to have been used as a processing area for turkeys and rabbits, and the same site also had turkey eggshells, suggesting strongly that these were domesticated rather than wild turkeys.

Dogs, wild birds, and carnivorous mammals are found mostly as burials throughout Ridges Basin, with some accompanying human burials. This is in contrast to McPhee Pueblo, which as mentioned above had high numbers of wild birds, where remains of ritually important animals like these were found in association with ritual structures. There is no such association anywhere in Ridges Basin, suggesting that while these animals were likely ritually important in both areas, the exact nature of the associated ritual differed.

As for artiodactyls, here as elsewhere they were found in greater numbers at the only aggregated site cluster that can be considered a village: Sacred Ridge. Since this site also has higher numbers of projectile points and processing tools, Potter suggests that the artiodactyls were the result of more effective hunting parties drawn from the larger village population, rather than evidence for special status of the residents of Sacred Ridge or special feasting being conducted there. There are a lot of unusual features to this site, however, so it’s hard to know how to interpret it.

That concludes Potter’s analyses. He ends the chapter with some conclusions that they suggest. First, as seen in multiple analyses, large sites tend to have more artiodactyls than small ones, probably because larger, more aggregated settlements allowed for the building of cooperative hunting parties that were more effective at taking down large game. This was a definite material advantage to community aggregation and the formation of villages, a key characteristic of the Pueblo I period that has led to a lot of questions about why and how it happened. It’s noteworthy, however (although Potter doesn’t note it) that the Pueblo I villages were as a rule short-lived and many seem to have been abandoned under duress, so the greater cohesiveness that allowed for these more effective hunting parties seems to have had definite limits under the circumstances.

Another pattern that emerges is the association of some sites with marshes and the extensive use of waterfowl, and presumably other marsh resources, at these sites. Potter connects this with the general importance of marshes, lakes, and other water places in Pueblo religion and ritual, as well as with the later artificial reservoirs built in the Mesa Verde region. It’s possible that an initial tendency to settle near wetlands because of their practical advantages in terms of resources led over time to a more metaphysical attitude toward watery places, although this remains highly speculative.

There is also a tendency over time for a shift in the contexts in which remains of animals of presumed ritual significance, like wild birds and carnivorous mammals, with early sites such as those in Ridges Basin having them largely associated with burials and the ceremonial “closing” of residential sites, whereas at later sites such as those in the Dolores area they are more associated with communal ritual structures. This suggests a shift in use of these religious symbols from the private to the public sphere, which Potter notes has also been proposed over the same period for the use of red ware pottery, which also likely had ritual significance. This shift may have continued into the rise of the Chacoan system, with its increased focus on monumental architecture presumably associated with public ritual.

Finally, Potter notes the early importance of turkeys in Ridges Basin, which could be due to general environmental differences across the region but may also reflect earlier depletion of large game in this area compared to others. There is a general pattern through Pueblo prehistory of increasing use of turkeys for meat as artiodactyl use declines, presumably in response to overhunting of local populations. On the other hand, one intriguing thing about the greater use of domesticated turkeys at the eastern edge of the Mesa Verde region during Pueblo I is the genetic evidence showing that domestic turkeys in the Southwest are likely more closely related to wild subspecies found to the east than to those found locally. Could the use of turkeys in Ridges Basin reflect early contacts with peoples further east? Potter doesn’t mention this possibility, and I don’t know if there is any other evidence of such contacts, but again, intriguing.

So, yeah, this chapter is a lot more focused than those coming before it, but the results of its analyses are intriguing. As more evidence becomes available from other regions with Pueblo I populations it may be possible to extend these sorts of comparisons further.

Bone Tools at Chaco Museum

Bone Tools at Chaco Museum

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Mt. Taylor from Chaco

As I’ve discussed before, the patterns of use and importation of chipped stone at Chaco are somewhat puzzling. Unlike many other commodities, such as wood, corn, and pottery, which were imported from specific distant locations within the Chacoan sphere of influence in astonishing quantities during the height of Chaco’s regional power, chipped stone seems to have been largely a mundane, utilitarian concern. Throughout all periods of Chaco’s occupation most chipped stone was local. At Chaco’s peak of power and influence between AD 1020 and 1130 there was a slight uptick in imports of stone, particularly a distinctive pink chert from the Narbona Pass area to the west.

As I noted in the earlier post, however, obsidian follows a different pattern from the other imported stones. It is most common not at the height of Chaco’s regional power in the eleventh century but much earlier, in the Basketmaker III period between AD 500 and 750, when it is the most common nonlocal type of chipped stone. This was a time when Chaco may have seen an earlier period of regional importance, although figuring out what was going on at this time is very difficult for several reasons. By the Pueblo I period the amount of obsidian seems to drop precipitously, and it doesn’t start to recover until the very end of Chaco’s period of Pueblo occupation after AD 1120. This pattern puts obsidian decidedly out of phase with most other material culture imports to the canyon, which tend to correlate with the well-known evidence for social complexity and monumental architecture that we associate with the Chaco Phenomenon.

A recent paper by Andrew Duff, Jeremy Moss, Tom Windes, John Kantner, and Steven Shackley tries to put the obsidian evidence on a firmer footing by using geochemical sourcing to identify the source outcrops for a broad sample of obsidian found at Chaco and at various Chacoan outlier communities in the San Juan Basin. As they note, this is the latest chapter in a complicated story. Way back in the 1980s, the Chaco Project did an extensive sourcing study of obsidian found in its excavations in the canyon using X-ray fluorescence (XRF), a non-destructive sourcing technique that was then relatively new in archaeology. Their results, reported by Cathy Cameron in a number of publications, were surprising. They seemed to show that the closest source of obsidian, Mt. Taylor, provided very little of the obsidian found at Chaco (about 4%), while a distant source, Red Hill in Catron County, New Mexico, provided a very high proportion, especially in the assemblages from earlier sites. Also well-represented was obsidian from the Jemez Mountains, the second-closest source, with the proportion of Jemez obsidian increasing over time, a common pattern in the northern Southwest.

This seemed to indicate that there were substantial early ties between Chaco and the Red Hill area, far to the south but still just barely adjacent to some known Chacoan outliers. This result was mentioned in many publications on Chaco over the years, although many people didn’t really seem to know what to think of it. However, it soon began to be questioned. After this initial sourcing study had been done, Tom Windes submitted some samples of obsidian from Pueblo Alto and the Spadefoot Toad site for obsidian hydration dating, which involved a sourcing analysis as an intermediate step in the dating process. These analyses were inconclusive when it came to dating the artifacts (not uncommon in the Southwest, where obsidian hydration has a poor record as a dating technique), but the sourcing portion suggested strongly that the samples that had previously been sourced to Red Hill instead came from Mt. Taylor. Windes mentioned this anomaly in his site reports, as did Cameron in her subsequent publications on the subject, but a full published account didn’t appear until this new study.

The new study also used XRF to do the sourcing analysis, but both analytical techniques and source characterizations have improved considerably since the 1980s, so the results were quite different from the first effort. For some reason this study was unable to do a complete reanalysis of the earlier samples (although it implies that this may be possible in the future), so there was only limited overlap and the focus was mostly on recent samples collected by Windes at Basketmaker III and Pueblo I site in and around Chaco, as well as outlier sites studied by Kantner in the Red Mesa Valley near Mt. Taylor and by Duff at the southern edge of the Colorado Plateau near Red Hill.

The results were not really surprising, in that they have been known in broad outline since Windes submitted his samples for dating and reported on the sourcing anomalies, but it’s nice to see them formalized in a peer-reviewed paper. Basically, this study found that no samples from Chaco came from Red Hill, although a few came from other sources in the same general area, and that the most common source found at Chaco was Mt. Taylor. Over time there was a trend in the Chaco data showing a shift from Mt. Taylor to Jemez sources, accompanied by the well-known trend toward less obsidian in assemblages overall. The sample from the Blue J site near Mt. Taylor, in contrast, showed high proportions of Mt. Taylor obsidian increasing over time, in marked contrast to the Chaco pattern. The southern sites showed assemblages of obsidian almost entirely composed of Red Hill and other nearby sources.

Basically, the overall pattern was a classic distance-decay distribution, where the prevalence of a given source at a given site was mostly predictable by the distance between the source and the site. This is in sharp contrast to the pattern for many other imported goods at Chaco, which are present in high quantities in the source areas and at Chaco but not in between. This suggests strongly that obsidian was not part of any general Chacoan exchange system(s) but was procured by individual communities in accordance with their own needs, mostly using the closest sources. This is in keeping with the general tendency for chipped stone to be a relatively low-priority commodity in these societies.

The paper mentions the decline in overall abundance of obsidian after the Basketmaker III period at Chaco, but doesn’t spend much time discussing it beyond saying this:

The overall decrease in obsidian use noted at Chaco sites may reflect a shift in technological focus away from hunting and a subsequent focus on grinding technology as agriculture becomes the dominant subsistence strategy.

As I’ve noted before, this is almost certainly wrong; the decrease in question occurs at the end of the Basketmaker III period, at which time there is considerable evidence that Southwestern populations were already heavily dependent on agriculture. The decrease in obsidian is still odd, though. One thought I’ve had to explain it is that maybe the obsidian from after this period isn’t actually missing at all, but is at Pueblo Bonito, which had lots of obsidian but was excavated a long time ago using techniques that aren’t really comparable to the modern techniques used by the Chaco Project and later efforts that resulted in the collections being analyzed here. I would suggest that an XRF sourcing analysis of the Bonito obsidian would be interesting. As it is, there’s a huge shift in the proportions of the different sources at Chaco between Basketmaker III and Pueblo I. The earlier samples (dominated by the huge samples from the major villages of Shabik’eschee and 29SJ423) show a predominance of Mt. Taylor obsidian, while the later ones show mostly Jemez sources. The sample size is so much smaller for the later period, however, that I’m skeptical about taking this flip at face value. Including the Bonito assemblage might help to bridge this gap, or at least explain it.

Finally, it’s again noteworthy how unimportant obsidian appears to have been to the Chaco system. Even if the Pueblo Bonito evidence ends up indicating a more important role at Chaco itself, the various outlier communities appear to have used local sources and to have followed their own priorities in acquiring this commodity rather than getting it through any Chaco-controlled or -oriented system. This is one of the ways that Chaco appears to diverge from Mesoamerican societies, despite recent evidence that it may have had more contact with them than was previously believed. Obsidian was hugely important symbolically in Mexico, and control of major sources was a major source of power and wealth for various Mesoamerican polities. In the Southwest, however, nobody seems to have cared that much about controlling major obsidian sources, and obsidian seems to have been distributed as a fairly ordinary commodity without any particular symbolic importance. I think this is one of the strongest pieces of evidence suggesting that whatever influence Mesoamerican societies may have had on Chaco was indirect and mediated by Chacoan elites rather than imposed directly from Mexico, as some have argued.

In any case, while this isn’t really the most exciting paper, it’s still an important one in straightening out a part of Chacoan archaeology that had become pretty confused. Obsidian may not have been all that important at Chaco, but it’s still worth studying in part precisely because of its mundanity.
Duff, Andrew I., Moss, Jeremy M., Windes, Thomas C., Kantner, John, & Shackley, M. Steven (2012). Patterning in procurement of obsidian in Chaco Canyon and in Chaco-era communities in New Mexico as revealed by X-ray fluorescence Journal of Archaeological Science, 39 (9), 2995-3007 DOI: 10.1016/j.jas.2012.04.032

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USGS Sign, Anchorage, Alaska

One hundred years ago today, one of the biggest volcanic eruptions in recorded history took place in southwestern Alaska. The volcano, known as Novarupta, is located in what is now Katmai National Park, which was established in 1918 as a direct result of the eruption and its effects on the landscape. As a result, this anniversary is a big deal for the National Park Service in Alaska, which has a special issue of its journal Alaska Park Science devoted to the eruption as well as a special webpage of information on volcanoes in the region. The main institution involved in Alaska volcanology, however, is the Alaska Volcano Observatory, a joint program of the US Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the State of Alaska Division of Geological and Geophysical Surveys. They are spearheading much of the commemoration of Novarupta and have their own website listing events and other information on it.

The eruption of Novarupta began on June 6, 1912 and continued for three days. There are various contemporary reports of the eruption from people who were in the area at the time, including one by I. M. Dailey of the US Coast and Geodetic Survey, who was stationed 150 miles away in Seldovia at the time, which was soon published in the Bulletin of the American Geographical Society and is now available free through JSTOR. Other reports come from the larger town of Kodiak, even closer to the eruption, where a foot of ash fell in the course of sixty hours of darkness. A fuller picture of what had happened at the site of the eruption itself didn’t emerge until a series of expeditions over the next few years sponsored by the National Geographic Society traveled to the vent site and undertook a variety of studies that had an enormous impact on the emerging field of volcanology. In an article in the aforementioned special issue of Alaska Park Science Judy Fierstein, a USGS volcanologist who has done extensive research at Novarupta and other volcanoes at Katmai, summarizes both the early reports and studies and more recent work that has clarified the reconstruction of exactly what happened over those three days in 1912.

Many of the early National Geographic expeditions were led by the botanist Robert Griggs, who would be quite influential in shaping interpretations of Novarupta. He discovered and named Novarupta itself, although Fierstein notes that he actually concluded erroneously that the main vent for the eruption was not there but at Mt. Katmai six miles away, which collapsed dramatically into a huge caldera during the event. Subsequent research has revealed, however, that while most of the magma that erupted was indeed stored in a chamber under Mt. Katmai, it actually erupted through Novarupta. Understanding exactly how this complicated internal “plumbing” system of the two volcanoes worked is one of the continuing challenges in ongoing research on the eruption.

Griggs also discovered and named the famous “Valley of Ten Thousand Smokes” where flows of ash from the eruption filled a large valley downslope from Novarupta. At the time Griggs visited just a few years after the eruption, this valley was filled with steaming fumaroles where the still-hot ash met various water sources, and the astonishing sight prompted the poetic name. Within a few more years, however, most of the fumaroles had stopped steaming, and they’re pretty much all dead now. Still, the name remains, as does the strikingly barren landscape with little vegetation having recovered even a hundred years later. The area is so otherworldly that it was actually used as a training ground in the 1960s for astronauts preparing to go to the moon.

Remarkably, despite the scale of Novarupta, which ejected more than three cubic miles of magma in the form of a cloud of ash thousand miles wide and 100,000 feet high that wind currents eventually carried as far as Algeria, there were no deaths from the eruption. The inhabitants of the three Native villages near the volcano had fled after a series of earthquakes in the days leading up to the eruption indicated that a major catastrophe was likely, and the few other communities in this sparsely populated area were far enough away that the levels of ash fall they received were substantial but not deadly. Even Kodiak, which was the hardest hit community due to both proximity and wind direction, managed to get through the initial period of fear and panic during which the whole population took refuge on a Coast Guard cutter docked in the harbor, and it soon recovered its earlier prosperity. The residents of the three closest villages were unable to return to their homes, of course, and were resettled in other communities elsewhere on the Alaska Peninsula, where their descendants reside to this day. All this is in striking contrast to the death toll of over 36,000 people from the eruption of Krakatoa in 1883, which was of a similar magnitude but occurred in a much more densely populated area.

Indeed, the lack of major cultural or long-term environmental effects from Novarupta (outside of the immediate area, of course) initially led one prominent archaeologist, Don Dumond of the University of Oregon, to initially discount the role of volcanic eruptions in general as a force shaping the culture history of the Alaska Peninsula. Dumond conducted long-term excavations primarily in the Brooks River area of Katmai National Park from the 1950s to the 1980s, and his interpretations based on that work have been enormously influential in shaping interpretations of the region’s prehistory. Initially he saw no particular correlation between the numerous volcanic ash layers in his Brooks River sites, which he assumed came from eruptions of the numerous local volcanoes, and the cultural changes visible in the archaeological record. More detailed geophysical work on the ash itself, however, led one volcanologist to suggest that some of the larger ash layers at Brooks had come from various known eruptions at Aniakchak, a very large volcano about 150 miles further south on the Peninsula. If eruptions had deposited ash that far away, they must have been much larger than Novarupta, which would therefore not necessarily be a good guide to their ecological or cultural effects. Dumond therefore decided to look over the record of ash deposits and culture history in other parts of the peninsula to determine if these ash layers really were as widespread as they should be if they came from Aniakchak or another very large volcano.

He published his findings in a 2004 paper, and the results were intriguing but inconclusive. Many other sites on the Peninsula did have ash layers that could potentially be from the same eruptions as the major Brooks River ones, but difficulties in precisely dating these layers and relating them to the dating of the known eruptions at Aniakchak left the issue largely open. While this particular study was largely inconclusive, I find the general idea of trying to determine the relationships between volcanoes and human history very interesting (as longtime readers will recall), so hopefully more research along these lines in this exceptionally volcanically active area will shed more light on the question, which is potentially of great importance in explaining certain cultural and linguistic phenomena.

Regardless of whether volcanic eruptions were major factors in the prehistory of Alaska, it’s clear that they are a major risk factor for us today because of a new development since 1912: the rise of air travel. We need only recall the havoc wreaked by the eruption of Eyjafjallajökull in 2010 (a vastly smaller eruption than Novarupta) to realize how big an effect a major eruption can have on aircraft, and southwestern Alaska is one of the most heavily traveled air routes in the world for both passengers and freight. Indeed, one of the main reasons the Alaska Volcano Observatory was established was to monitor Alaska’s volcanoes for their risk to air traffic. One study using simulations based on the scale of the Novarupta event found that a similar event today could potentially shut down essentially all air traffic throughout the northern hemisphere (and, in the unlikely event that ash moved into the southern hemisphere as well, even the whole world). And note that this is by no means an extremely unlikely occurrence; eruptions of this scale happen regularly, and while there hasn’t been one since Novarupta, there’s every reason to think another one will happen at some point. The only thing to do is to keep watching the volcanoes and studying their past eruptions to try to glean insights for the future. This hundredth anniversary of one of the most important such eruptions is an excellent opportunity to remember that.
Dailey, I. (1912). Report of the Eruption of Katmai Volcano Bulletin of the American Geographical Society, 44 (9) DOI: 10.2307/200811

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Earthquake Park, Anchorage, Alaska

On this date in 1964, which happened to be Good Friday, the largest earthquake in US history struck Southcentral Alaska. With its epicenter in Prince William Sound and its magnitude measured as 8.6 or even higher on the Richter Scale, the Good Friday earthquake caused massive destruction throughout the region. The nearby town of Valdez was completely destroyed and later rebuilt on a different, less seismically vulnerable site. Other towns such as Seward and Whittier didn’t suffer that fate, but 13 of the 70 residents of Whittier died in the quake and the following tsunami, and port facilities both there and in Seward suffered so much damage that they have never fully recovered their economic importance.

Anchorage, which was a bit further away, suffered somewhat less, although it was still hit hard. Indeed, its port managed to stay open in the aftermath of the quake and tsunami, which was one of the factors making Anchorage become the main economic center for the region and the whole state in the following years. This is not to say that the earthquake wasn’t a major disaster for Anchorage as well, however. The city was built on sediments that turned out to be pretty vulnerable to shifting when hit with an impact of that scale, and parts of the downtown were literally torn apart. An upscale residential area known as Turnagain Heights suffered a landslide so devastating that the city, rather than attempt to rebuild, designated it as a park. It is now aptly named Earthquake Park, and while there isn’t much obvious evidence of the effects of the earthquake anymore, there are interpretive signs that tell the story quite effectively.

Sign Describing Turnagain Heights Landslide, Earthquake Park

Earthquakes are a fact of life in Alaska, which just north of the area where the Pacific Plate slides under the North American Plate (known as the Aleutian Trench). This movement is continual, but it only occasionally occurs in the form of massive slips of the sort that cause earthquakes on the scale of the one in 1964. The more usual effect is to warp and compress the land of Southcentral Alaska. This warping, along with other factors such as glaciation, leads to complicated changes in sea level over time, changes which can vary substantially in areas only a few miles apart.

And that, in turn, greatly complicates study of the archaeological record of Alaska. Rising sea level typically destroys archaeological sites (although in certain very specific circumstances it may instead preserve them in excellent condition), and changes in sea level over time may make sites from a given time period difficult to locate even if they haven’t been submerged. Furthermore, cultures of coastal Alaska have generally been oriented toward the sea, with settlements typically located fairly close to wherever the coastline was at the time. This means that sea-level fluctuations have even more profound impacts on understanding the archaeological record here than they might in some other areas.

Interpretive Signs at Earthquake Park

These factors are illustrated dramatically in a 1996 article by Aron Crowell and Daniel Mann reporting on research in Kenai Fjords and Katmai National Parks attempting to carefully document sea-level changes and their effects on the archaeological record. These two parks are not very far from each other, being about 200 miles apart and both located on the coast of the Gulf of Alaska, but their geological and cultural histories differ dramatically. Kenai Fjords, as its name implies, is dominated by coastal fjords created when rising sea level inundated glacial valleys. Its archaeological record is sparse and limited to the past few centuries.

Katmai, on the other hand, has a relatively stable coastline and an enormously rich and well-documented archaeological record dating back several thousand years. Much of what is known about the archaeology of southwestern Alaska is based on long-term research in various parts of Katmai by Don Dumond of the University of Oregon from the 1950s through the 1980s, and there has been considerable additional research since then. The cultural sequence in this area closely parallels that of the nearby Kodiak Archipelago, which was one of the most densely populated parts of Alaska when the Russians arrived in the eighteenth century. The Kenai Fjords area, on the other hand, had a much lower density at this time, as did Prince William Sound further east, with which it has many similarities. This lower density has been plausibly attributed to lower resource productivity in these areas, but Crowell and Mann point out that the extremely low density of prehistoric archaeological sites in Kenai Fjords is perhaps also due to geological processes and seal level change.

Welcome Sign, Earthquake Park

To investigate the differences between the two parks, Crowell and Mann intensively investigated certain parts of each, with intriguing results. One of the areas investigated in Kenai Fjords was a narrow sand spit with a series of beach ridges containing a total of four archaeological sites (most dating to the eighteenth and nineteenth centuries and the earliest about 500 years old) and a small tidal pond surrounded by trees killed when the 1964 earthquake caused the land to drop about one meter, exposing their roots to the seawater that permeates the sandy soil. This same seawater also fills the pond, so the sediments in and around it could be interpreted as a record of changes in relative sea level over time. Digging down in search of radiocarbon-datable material, the archaeologists found a series of buried tree stumps 1.8 meters below the present surface that seemed to have been killed in a sudden cataclysm surprisingly similar to what happened in 1964. Six radiocarbon samples taken from the bark of these stumps gave dates that were statistically identical and averaged out to about AD 1170.

This strongly suggests that there was a major earthquake at least as strong as the Good Friday one in or around 1170. This is consistent with evidence from several other parts of the region, where other studies have found less precise evidence for major geological changes around this time. The implication for the issue of archaeological site preservation is that any coastal sites in this area predating 1170 would have been destroyed by the earthquake. Since the geomorphology of Kenai Fjords means that the only usable settlement locations here are on low coastal sand spits like this one, this earthquake probably completely destroyed the previous archaeological record. This would explain why there are so few sites in the park, and why they basically all date to the late prehistoric period or later. The relatively low productivity and other drawbacks of the area may well have limited population earlier as well, but with the earthquake having destroyed any evidence of what was going on previously there’s no way to know for sure.

Sign Describing the Good Friday Earthquake, Earthquake Park

Katmai was a different story, however. Crowell and Mann discovered 22 new sites there in the course of this project (as compared to 16 sites total in Kenai Fjords documented by this and other projects), suggesting that further survey along the coast will likely reveal even more as yet unknown sites in this very productive area. Interestingly, many of the sites they found were located away from the present coastline, often in uplifted areas that may have been coastal at times of higher sea level than at present. Radiocarbon dates from these sites and from peats in the intertidal zone allowed Crowell and Mann to reconstruct a tentative sea level curve for much of the past several thousand years, with the main conclusion being that sea level has been pretty consistent over the past 4000 years, with a slight rise sometime in the past couple hundred years, possibly as a result of subsidence of land in the 1964 earthquake. (Crowell and Mann don’t discuss the possibility that global sea level rise as a result of climate change may be another explanation for this, but it strikes me as plausible.) In any case, whatever the source of this slight recent rise in sea level, it had few apparent effects on archaeological site preservation beyond contributing to the exceptional preservation of one waterlogged site. The subsidence from the 1964 earthquake was very slight in this area, and this appears to have been true for the 1170 one as well. The rich archaeological record of the Katmai coast, then, appears to be in part a function of the relative stability of sea level in this area over thousands of years, in striking contrast to areas just a few hundred miles away.

The archaeological record is always incomplete, and any conclusions drawn from it have to be tempered by knowledge of that incompleteness. As this paper demonstrates very effectively, however, the factors determining just how much of the past is left for us to study vary a lot, especially in places like Alaska where the forces of the earth are exceptionally active. The modern population of Alaska learned just how active those forces can be in 1964, and it stands to reason that the ancient population learned the same lesson in 1170.

"Living with Earthquakes" Sign, Earthquake Park

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Delaney Park at Noon on the Winter Solstice, Anchorage, Alaska

Today is the winter solstice, which means two things: the anniversary of the beginning of this blog (three years now), and the shortest day of the year.  Up here in Alaska, the second is particularly noteworthy.  We had about five and a half hours of daylight today; officially, the sun rose around 10:15 and set around 3:45.  In Anchorage, however, which has mountains to the east, the sun didn’t actually appear until about 11:00.  The state likes to emphasize the converse of this phenomenon in summer in their promotional material, of course, hence the idea that Alaska is the “Land of the Midnight Sun,” but in the winter the “Twilight Noon” is equally appropriate.  Indeed, for the parts of the state that are below the Arctic Circle (most of it), it never gets completely dark or completely light for 24 hours straight, so the Midnight Sun never strictly appears even on the summer solstice.  Noon on the winter solstice definitely does start to look pretty similar to twilight, though.

I’ve talked a lot about archaeoastronomy in the Southwest on this blog, which is why marking events like the solstices has been such an important part of it, but as far as I can tell there is no evidence that the native people up here paid much attention to astronomical phenomena.  (It’s quite possible that they did and I just haven’t found the documentation of it, of course.)  This could be because of the lack of an indigenous agricultural tradition, since calendar-making has generally been linked to agriculture, although of course seasonal events like salmon runs are often very important to non-agricultural people and it would presumably be helpful to have a means of marking them.  I believe navigation by the stars was pretty well developed among some of the more maritime-oriented societies of the North, which makes sense given the general lack of landmarks along the Arctic Ocean coastline, but use of the sky to tell time doesn’t seem to have been as important.  Presumably people just paid more attention to other time markers.  This is a topic I should definitely look into.  Anyway, happy solstice, and thanks for reading.

Captain Cook Statue at Noon on the Winter Solstice, Anchorage, Alaska

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