Regional volcanic hazard investigations require an in-depth understanding of a region' spatial and temporal distribution of volcanic vents and variations in eruption rates. Usually assessments are based solely upon the distribution of vents and eruptive centers exposed at the surface. These assessments commonly assume relatively simple tectono-magmatic settings and evolutions (e.g. Connor et al., 1992; Conway et al., 1998). Hazard studies within tectonically complicated regions, such as the Basin and Range of the western USA (e.g. Yucca Mountain, Connor et al., 2000; Valentine and Perry, Chapter 19, this volume), have demonstrated the need for more accurate knowledge of the regional volcanic stratigraphy. In this chapter, we describe an analysis of volcanic hazards that includes this more comprehensive view of volcano stratigraphy. Such detailed investigations, accounting for differential subsidence and the burial of older volcanic features, can vastly improve the accuracy of any volcanic hazard assessment.
The Idaho National Laboratory (INL) comprises several nuclear facilities, including the oldest power reactor in the world (see Chapman et al., Chapter 1, this volume). The INL is located in a region of volcanic hazards stemming from its position on the eastern Snake River Plain (ESRP). The ESRP is one of the most volcanically active regions in North America. Recent volcanism on the plain is characterized by the effusion of very low viscosity lavas. The resulting lava flows are often 10m thick, but inundate vast areas, up to 1500 km. Volcanism on the ESRP is predominantly monogenetic, meaning that renewed volcanic activity and accompanying lava flows form from new batches of melt and issue from new volcanic vents (see Connor et al., Chapter 3, this volume).