Too small to fail
We usually think of archaeologists as digging up and recording remnants of past civilizations, but interpretation is another important part of the scientists’ work. When Arizona archaeologist Mark Elson investigated prehistoric sites along the route of a planned highway expansion, he not only unearthed potsherds, stone tools, and other artifacts, but he also found evidence of a successful mass resettlement of people following the eruption of an ancient volcano.
The details of that adaptation to a catastrophe that took place about 900 years ago may help prevent human losses due to volcanoes, earthquakes, and hurricanes today. Elson, a project director at Tucson-based Desert Archaeology Inc., is the latest speaker in the Southwest Seminars series Ancient Sites & Ancient Stories. His topic for a Monday, May 17, lecture in Santa Fe is “Human Adaptation to Catastrophic Events: Lessons from the 11th Century A.D. Eruption of Sunset Crater Volcano.”
The research related to his talk began when his company won the contract to document 40 prehistoric sites along U.S. 89 between Flagstaff and the Utah border. Beginning in 1998, Elson worked with volcanologists and geomorphologists from Northern Arizona University and with representatives of the Hopi Tribe, pursuing two lines of inquiry. One was to illuminate the details of an apparently successful adaptation to the eruption of Sunset Crater Volcano (about five miles east of the highway) by local people — the Sinagua, as 1930s archaeologist Harold Colton called them. The other was to try to confirm the relationship of those people to the Hopi.
“Sunset Crater was an example of a particularly good adaptation,” Elson said by phone from his office at Desert Archaeology. “The people not only survived but thrived and ended up building some of the largest Pueblo structures in the Flagstaff area.”
An important finding of the U.S. 89 team was that, after the eruption, a thin layer of volcanic cinders acted as a water-retaining mulch on the landscape. This “cinder mulch” opened to farming large areas that previously had no agricultural value. The Sinagua people flourished there, building an impressive rock-walled pueblo whose ruins today are the showcase of Wupatki National Monument.
Elson said the people were able to adapt to the volcanic catastrophe because of a number of preadaptations. “They lived in very small groups, with the largest sites having only 30 to 50 people. They likely had a large kin network outside of the eruption area, and they had a limited social hierarchy, so decision-making was done at the household level or a level just above that. So they could make the decisions and move easily.
“Also, they didn’t have a lot invested in their infrastructure; they could easily rebuild their houses within a couple of weeks. They already knew how to grow crops, and because of the scant rain and growing season, they had a risk-reduction strategy, doing lots of small plots in micro-environments, so an eruption might not damage all their crops.”
Another factor was that this catastrophe was a volcanic eruption, and volcanoes don’t blow up without warning. Local earthquakes warn that an eruption is imminent. People in Michoacán, Mexico, felt quakes begin 45 days before Parícutin Volcano started erupting in 1943. The tremors gradually increased in frequency until, the day before the blast, 300 small quakes occurred.
The eruption of Parícutin, which is considered a “twin” to Sunset Crater Volcano because of its similar type, had an immense impact on thousands of the native Purépecha (Tarascan) people. The eruption covered nearly 10 square miles with lava and another 70 square miles with ash and cinders too thick for agriculture to be done. But nobody died in the eruptions, which lasted almost 10 years.
Elson and Northern Arizona University’s Michael H. Ort, his chief colleague on the U.S. 89 project, obtained a grant that allowed them to visit Michoacán in 2003. Elson interviewed people about the eruptions, and the two collected samples from older trees in the area. The samples, with help from tree-ring analysis and a process called “laser ablation inductively coupled plasma mass spectrometry,” showed elevated levels of certain chemicals typically thrown into the air during volcanic eruptions. That technology, which was used to analyze wood samples from the Parícutin eruptions, is being employed at Sunset Crater.
“We’re still working on this, but we think the eruption occurred in the A.D. 1080s,” Elson said. “There’s an old, famous A.D. 1064 date that came out of research done in 1958, but our team disputes the evidence. True, it’s only a 20-year difference, but it is a big difference in terms of human adaptation. The earliest date we have for Wupatki is 1106, and if the eruption was 1064, that’s [almost] 50 years, so you wonder, why did they wait 50 years to resettle down there? The argument is that maybe they didn’t understand the cinder mulch, but I don’t buy that. These people lived in a cinder field. There are 600 cinder cones in the area, and they had done agriculture there.
Parícutin Volcano eruption, circa 1943; photo by Ted Nichols
Excavated roomblock at the Homestead site (NA 181), which was occupied from 1075 to 1150 A.D., during the era of the Sunset Crater eruption