Abstract by Katie Barton
Links between eruptive styles, magmatic evolution, and morphology of shield volcanoes: Snake River Plain, Idaho
Despite their similar ages and geographic locations, two low-shield volcanoes on the Snake River Plain, Idaho, Kimama Butte (87 Ka) and Rocky Butte (95 Ka), have strikingly different profiles. In this study, these two volcanoes are examined to determine the connections between chemical composition, intensive parameters, eruption style, and topographic features of basaltic shield volcanoes. Because lava temperature, magma viscosity, and chemical composition overlap at the two volcanoes, they are probably not important controls of shield volcano morphology. The main difference at the two shields, aside from general vent morphology, is the presence of late-stage, plagioclase-rich, high-viscosity lavas that form the high spatter ramparts at Kimama Butte but are missing at Rocky Butte. From this study, we conclude that eruption style plays the most important role in developing a low-shield volcano summit. Where eruptions shifted from lava lake overflow and tube development to late fountaining with short spatter-fed phenocryst-rich flows with higher viscosities, a steeper, higher shield developed.