Volcanoes Giveth, and Taketh Away

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.