5 D4. Tectonics, Petrology, Volcanology, and Impact Craters

Monday, 19 April 2021
8:00 AM - 12:00 PM
Missouri State University- Geography and Geology MS Program Room

RHEOLOGY OF THE ANDESITE ERUPTED FROM FISSURE 17 OF THE 2018 KILAUEA LOWER EAST RIFT ZONE ERUPTION

Paper number: 5-8
Program: Technical Sessions
Time: 10:10 AM – 10:20 AM

Authors

Abstract

In 2018, basaltic lava erupted on the Lower East Rift Zone (LERZ) of Kilauea, Hawaii. Of the 24 identified vents, 23 erupted basalt, while one produced lava with a bulk andesitic composition. This complex lava is fissure 17 which was active from May 13-25 of 2018. We collected 5 samples of fissure 17 lavas. These rocks contain both microlites and coarse-grained phenocrysts of plagioclase, two pyroxenes, and no olivine. Mixing of two different lavas is visible on a centimeter-scale, with a glassy trachytic fine-grained matrix; the other with a dark cryptocrystalline matrix, large rounded vesicles, and large euhedral crystals of plagioclase. This has been interpreted as resulting from fresh basaltic lava encountering a cool crystal-rich mush pocket from a previous magmatic episode. The petrology, density, rheology, and thermal properties of fissure 17 lavas will be further investigated, and compared with the voluminous fissure 8 eruption, to better understand the variety of physical properties and behaviors that can be exhibited by lava flows erupted within a single fissure zone eruption at Kilauea. The viscosity of the lava will be measured using both uniaxial compression (parallel-plate viscometry) and oscillatory shear (dynamic mechanical analysis, DMA). Compared to the hotter, less crystal-rich lava that is fissure 8, our preliminary hypothesis is that lava viscosity at fissure 17 is higher due the higher crystal content, and lower eruption temperature - both consequences of mingling with the cooler crystal-rich mush pocket prior to eruption.

Geological Society of America Abstracts with Programs. Vol. 53, No. 3

doi: 10.1130/abs/2021NC-362772

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