The largest and potentially most devastating types of volcanic eruptions are known as super-eruptions. Such events are outside human experience, yet it is quite certain that they will occur in the future. Despite some public awareness of these rare but potentially devastating events, there is a shortfall of basic research into their ultimate origins, immediate causes, and environmental impacts. In North America, the most prolific source of super-eruptions for the past 16 million years has been the Snake River Plain-Yellowstone hotspot trace, stretching from SW Idaho and northern Nevada to Yellowstone itself. The most intense episode in this region occurred between ~12 and 9 Ma, with the eruption of the order of 10,000 - 20,000 km3 of rhyolite (for reference, the 1980 eruption of Mount St. Helens involved less than 1 km3 of magma). The magmas erupted during this flare-up were high-temperature rhyolites, an unusual type of magma that has been somewhat neglected in the past and only now is being thoroughly studied with respect to its origin, and behavior during large eruptions.
Perhaps the most important aspect of these magmas and the way they erupt is the sheer volume of magma involved in any one event, which largely determines the magnitude of the environmental impact. This and other aspects of the eruptions can only be reconstructed through detailed mapping of volcanic units in the field, a difficult project that requires the full-time attention of an experienced researcher. Therefore, this project will fund a post-doctoral researcher who will be charged with tying together different rock outcrops to establsh unit correlations and volumes, and to use these data to establish the volume and frequency of rhyolitic eruptions from the central Snake River Plain. The work will additionally involve mineral and chemical analysis to fingerprint individual units, and radiometric dating to establish absolute ages. All this information will be used constrain genesis and storage history of the rhyolitic magmas in conjunction with new and existing petrologic data. The results will help inform our understanding of Earth's continental crust during major episodes of volcanism (ultimately driven by unusually high heat flux from the mantle), and provide a basis for assessing the degree of enviromental disruption that might be expected from the next such event.
