Abstract

Widespread property damage and numerous fatalities, generated by worldwide volcanic activity, can be minimized through proper planning of mitigation procedures. Minimization of volcano-generated devastation requires candid communications between the scientific community, policy makers, and citizens; a thorough understanding of volcanic processes; identification of potentially active eruptive centers; and well-defined mitigation procedures.

Southwestern Utah experienced prolonged volcanism during Cenozoic time. Tumultuous eruptions of calc-alkaline volcanics and deposition of volcaniclastic debris dominated early to mid-Cenozoic volcanism. Mode and composition of late Cenozoic activity shifted to less destructive eruption of small, bimodal assemblages of basaltic and rhyolitic composition flows and plugs.

Active volcanic centers in the study area include the Sevier, Black Rock, and Escalante Deserts in the Basin and Range Province; the High Plateaus and adjacent areas in the Colorado Plateau province; and the Pine Valley Mountains-St. George Basin and surrounding areas. The youngest vents and flows in southwestern Utah are less than 1,000 years old. Hazards expected to accompany future volcanic activity include: loss or reduction of grazing, agricultural, and recreation lands; obstruction of transportation, communication, and power corridors; and damage or destruction to proximate buildings. Life-threatening hazards are not expected, but daily routines may be disrupted by lava flows where communities are near active vents. Residents of southwestern Utah should remember that, although volcanic threats exist the risk may be low.

Remote eruptive centers present Utah’s most imminent and potentially damaging volcanic hazards. Volcanic ashes, expelled to great heights, and carried aloft in atmospheric winds may settle over southwestern Utah. Ashes from prehistoric eruptions in California, Oregon, Montana, and other remote sources have settled over Utah during recent geologic history. Future eruptions in the Cascade Range may blanket southwestern Utah with abrasive volcanic dust and corrosive gases.