EFFECTS OF CINDER-CONE ERUPTIONS ON HUMAN POPULATIONS IN SOUTHWESTERN NORTH AMERICA

Studies of cinder cone eruptions in Arizona, USA, and Michoacán, Mexico, show that, although cinder cone eruptions are small to moderate in size, they can strongly affect local human populations. Cinder cone eruptions commonly take place in basaltic volcanic fields, many of which, in SW North America, have high elevations leading to higher-than-regional-average precipitation. The areas between cinder cones are commonly farmlands. Lava flows and deep cinder deposits may bury agricultural fields and villages, and alter landscape markers used as territorial boundaries. These and other cinder cone eruption effects have caused significant societal stress, migration, and conflict.

Sunset Crater erupted in the San Francisco volcanic field near present-day Flagstaff, Arizona, at ~1050-1100 CE, producing a >300-m-high cinder cone, basaltic lava flows that cover ~8 km², and a fallout blanket that covers >2000 km². Little Springs Volcano erupted in the Uinkaret volcanic field north of the Grand Canyon, Arizona, at ~1100-1200 CE. The spatter rampart is ~100 m high, and lava flows cover ~4 km². There is little cinder fall on the surrounding landscape. Parícutin erupted 1943-1952 CE in Michoacán, Mexico, producing a 424-m-high cinder cone, basaltic lava flows that cover ~25 km², and a widespread cinder blanket.

Human adaptation to the eruptions differed. Population migration occurred at Sunset Crater and Parícutin. At Sunset Crater, small groups migrated to lower elevations, where a decades-long precipitation increase and newly deposited cinder mulch allowed farming. There was probably little conflict with previous inhabitants, as there appear to have been very few people living in this area prior to the eruption. At Parícutin, five villages were affected, and thousands of people displaced. The Mexican government moved the villagers to new localities, but land disputes with prior residents led to at least 100 deaths. At Little Springs volcano, migration did not occur. Instead, new sites were built at the base of the lava flow, while structures and trails were built on the flow itself, and farming continued where the lava did not cover suitable land. At all three volcanoes, the lava flows are still not farmed. Although these eruptions were small, they dramatically affected the local environment and, hence, human populations.