Most research on human-environment interactions focuses on large-scale changes in environmental conditions over long periods of time (by human standards, at least). There are good reasons for this, especially when applied to prehistory, most importantly that there are a lot of potential data sources for environmental conditions that can be correlated with cultural chronologies to identify possible relationships between the two. A lot of research in the Southwest along these lines has sought to correlate periods of higher and lower average rainfall, readily apparent in tree-ring records, with population increases, decreases, and movements, as inferred from the number and types of archaeological sites in a given area, which conveniently can be dated with those very same tree-ring chronologies. Jeff Dean at the University of Arizona’s Laboratory of Tree-Ring Research has been a major figure in this sort of research for a long time, and it’s resulted in a lot of interesting insights and theories about Southwestern prehistory.
As we’re seeing right now in Iceland, however, there is another type of environmental event that can affect human societies: a short, intense, unexpected, and uncontrollable catastrophe like an earthquake or a volcanic eruption. These are generally harder to see in the paleoclimatological record, and as a result they are hard to correlate with cultural changes. Volcanoes themselves, however, are an exception to this invisibility, since they spew out all kinds of ash and lava that have very visible effects on the local geology. In many cases these can be dated by radiocarbon or other methods and correlated with events in the societies of the people living in the area. One very good example of this is found in Alaska among the northern Athapaskans. Another is closer to home, as it were, from the perspective of this blog: Sunset Crater.
Sunset Crater is northeast of Flagstaff, Arizona. It is the most recent of the San Francisco Peaks to erupt, and the only one to erupt during the time that humans have occupied the area. It erupted sometime in the mid-to-late eleventh century AD; the date 1064 AD gets thrown around a lot, based on some tree-ring samples at Wupatki that showed odd ring patterns in the few years after that, but this dating has been questioned and the general consensus is only that the eruption occurred sometime around this time, based on the (often quite large) deposits of ash found in sites from this period. Note that this is during the height of the Chacoan era. The eruption may have been visible at Chaco itself, and it was certainly visible at some of the outlying Chacoan sites, so the Chacoans, along with everyone else in the region, would definitely have been aware of the events even though the immediate area shows little to no Chacoan influence. It’s not clear how long the eruption lasted. Eruptions of cinder cone volcanoes can potentially go on intermittently for decades, although they can also be much shorter. Sunset Crater could have kept erupting for as long as 100 years or even 200, but more data are needed to determine this more precisely.
One theory about the effect of the eruption on human societies, first formulated by Harold Colton of the Museum of Northern Arizona in the 1930s, is that while the initial eruption was devastating to the small local population, the layer of ash that the eruption laid down turned out to be an excellent mulch, holding in much-needed moisture in this dry area and making agriculture much more productive, which spurred a massive influx of population to places like Wupatki that had been covered by ash and led to substantial cultural changes. This theory has since been challenged, and there is no real consensus today on what effect the eruption had on cultural dynamics in the area. It is highly unlikely, however, that it had no effect. A volcanic eruption is a big disruption to existing patterns of living.
One interesting and concrete manifestation of the effects the eruption may have had on local people comes from an interesting paper (which is my source for most of the general information about Sunset Crater above) on some building stones found at a nearby habitation site that show clear imprints of corncobs in them. The authors conclude that this could pretty much only result from people deliberately going to places where lava was coming out, probably small features known as hornitos that would have been easily approachable, and putting in offerings of corn cobs to let the lava run over them, then after the lava cooled taking the rocks back to the site (which is a few miles away) and forming them into building blocks with distinct corncob impressions. This would have been a lot of work, so it’s pretty apparent that it had a lot of cultural importance in some way.
Another interesting cultural connection to volcanoes is suggested in this article in the Alamogordo Daily News (via Southwestern Archaeology Today) about a salvage archaeology project south of Carrizozo, New Mexico, an area of considerable volcanic activity, that uncovered a large site that seems to probably date to around AD 900 to 1100, again during the Chacoan period. This era is not very well-understood in this part of New Mexico, which was occupied by the Jornada Mogollon who may have later played an important role in the origins of the kachina cult. One of the crew members, a woman from Santa Clara Pueblo, mentions that “where the lava comes out … represents the underworld.” The article is kind of confusingly written, so it’s not clear exactly what she means by that, but it’s a really interesting clue to the importance of volcanoes to Pueblo people. I don’t know much about the dating of the lava flows around Carrizozo, so I don’t know if the Jornada Mogollon would have been around to see the actual lava come out, but even if they didn’t they may have regarded certain vents and other features with reverence. They certainly used the resulting igneous boulders as a medium for their extensive and innovative petroglyphs.
I’m increasingly coming to think that the importance of sudden, catastrophic events like volcanic eruptions has received too little attention among archaeologists. Certainly long-term climatic changes are important, as are culture, political, and historical factors, but a catastrophe has a way of forcing changes very suddenly that may shed light on some of the more puzzling changes in the archaeological record. Something to think about as we watch the effects of a volcano in Iceland on people throughout northern Europe and beyond.
Elson, M., Ort, M., Hesse, S., & Duffield, W. (2002). Lava, Corn, and Ritual in the Northern Southwest American Antiquity, 67 (1) DOI: 10.2307/2694881