Start Date

5-2020 12:00 AM

Description

Despite their similar ages and geographic locations, two low-shield volcanoes on the eastern 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 on the differences in morphology. The main difference at the two shields, aside from general vent morphology, is the presence of late-stage, phenocryst-rich, high viscosity lavas that form high spatter ramparts at Kimama Butte but not at Rocky Butte. We conclude that phenocryst abundance, magma viscosity, and eruption style play the most important role in developing a shield volcano summit. Where eruptions shifted from lava lake overflow and tube development to late fountaining with short, viscous, spatter-fed, phenocryst-rich flows, a steeper, higher shield developed. The result can be used to better understand the eruptive processes of shield volcanoes on the Moon, Mars, and Venus that can only be studied morphologically.

Comments

Due to COVID-19, the Symposium was not able to be held this year. However, papers and posters were still submitted.

Available for download on Saturday, May 01, 2021

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May 1st, 12:00 AM

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 eastern 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 on the differences in morphology. The main difference at the two shields, aside from general vent morphology, is the presence of late-stage, phenocryst-rich, high viscosity lavas that form high spatter ramparts at Kimama Butte but not at Rocky Butte. We conclude that phenocryst abundance, magma viscosity, and eruption style play the most important role in developing a shield volcano summit. Where eruptions shifted from lava lake overflow and tube development to late fountaining with short, viscous, spatter-fed, phenocryst-rich flows, a steeper, higher shield developed. The result can be used to better understand the eruptive processes of shield volcanoes on the Moon, Mars, and Venus that can only be studied morphologically.