GIS ANALYSIS OF THE TYPES AND SPATIAL EXTENTS OF VOLCANIC HAZARDS IN MILLARD COUNTY, UTAH

The Black Rock Desert Volcanic Field (BRDVF) located in Millard County, UT, contains some of the youngest recurrent volcanism in the Basin and Range. This project aimed to identify the types of volcanic hazards and to quantify the spatial extent of future eruptive products from the Clear Lake Fault zone in the BRDVF. Numerous late Quaternary monogenetic volcanoes make up the volcanic field. The majority of their vents are associated with the Clear Lake Fault system which trends north-south along the center of Pahvant Valley. The most recent eruption was from the Ice Springs Volcano, 660ya. The Tabernacle Hill volcano is located a few km to the south and erupted 14,400ya. The biggest eruption in the state of Utah in the last 20,000 years occurred at the north end of this fault system, creating Pahvant Butte. Ash fallout distances suggests a VEI IV eruption produced at Pahvant Butte 15,500ya. The eruptive products of Pahvant Butte and Tabernacle Hill, as well as older Quaternary vents are cut by recent activity along the Clear Lake Fault. Most of the vents within the field have produced basaltic flows that have both ah’ah and pahoehoe textures. This study constructed a geographic information systems model consisting of digital elevation models, existing geologic maps, aerial photography, climatic data, and infrastructure shapefiles to map the extent of past lava flows and ash fall patterns, and to use these as a predictive tool for what could be possible in future eruptions. By buffering the known fault lines with both the maximum and minimum extents of the three most recent lava flows an estimation of the risk from lava flows was assessed. Lava flows pose a risk to ~70km of roads and highways in the County. The buffer analysis provides an overall estimation of how much farmland and state land lays within the potential lava flow hazard range for the BRDVF. This geologic buffer analysis approach provides a simple tool for exploring potential risk from volcanic hazards in monogenetic volcanic fields with vents along a well-expressed fault zone. Thus, it is potentially applicable at other areas around the world.