March 18, 2008 -- Some volcanoes destroy civilizations; others help them out.
That's the word from a new study of two small-scale volcanoes in central Mexico and northern Arizona, which had opposite effects on the nearby communities and are providing insights into how humans respond to volcanic eruptions.
The eruption of Mexico's Paricutin volcano from 1943 to 1952 disrupted agriculture and forced the abandonment of a large area.
About 1,000 years earlier, a similar eruption at Sunset Crater, Ariz., actually helped the soil, making less arable lands more fertile, says a multidisciplinary team of researchers. People there prospered by farming the better ground.
The discovery not only highlights two very different volcanic effects, but underscores some very different ways humans have responded -- and could respond today -- to natural disasters.
"We are inspired by the general dearth of studies of what people actually did in the past in response" to volcanic eruptions like these, explained geologist Michael Ort of Northern Arizona University in Flagstaff. Ort is the lead author of a paper about the two case studies, published in this month's issue of the Bulletin of the Geological Society of America.
Since it happened recently, the Paricutin case is unusually well documented. It started with an eruption in a corn field that went on to overtake an entire town. Geologists and anthropologists got first-hand experience of the eruption and how the locals responded to it.
"At that time in Mexico, farmers weren't thinking in geological terms," said archeologist Payson Sheets of the University of Colorado. "They were thinking in terms of an angry god."
The people created traditions that reinforce their memories of the eruption, Sheets explained, including an annual procession from the old cathedral -- now mostly buried by lava -- to the new town site. Similar traditions in other cultures help preserve historic information about volcanic disasters.
The Sunset Crater case was different in that the eruption there left thinner layers of volcanic material in many places. Instead of smothering the land, it acted like mulch and helped some soils become more arable.
In this way the eruption was a boon to local people, explained Mark Elson, a coauthor on the paper and archeologist for Desert Archeology, Inc., in Tucson.
Both cases also offer lessons to modern people, say the researchers, particularly in terms of emergency response.
"What we find is that the lower the level of social complexity, the better the response," said Elson. He cites, for example, hurricane Katrina, when communications at multiple levels complicated the response and victims were left to wait for help from the government.
"We are so trained to rely on hierarchies," Elson said. But the small families and extended family groups at Sunset Crater were on their own and could act appropriately to the major disruption and their displacement. "Probably nobody died at Sunset Crater...One of the lessons is to engage [emergency response plans] at the ward or neighborhood level."
Related Links:
Larry O'Hanlon's blog: Earth Impacts