75-21 Integrated Lab Analog and Numerical Modeling Study of Chilean Torta Domes

Session: Mineralogy, Geochemistry, Petrology, and Volcanology Student Session (Posters)

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Abstract:

New models are needed for the formation of flat-topped, steep-sided, extrusive lava domes because their style and timescale of emplacement are not well understood. Many lava models are intended for channelized flows and do not work for the crystal-rich torta domes in Chile’s Atacama region or the crystal-free Obsidian dome in southern California but dome spreading models might work for them. Samples of crystal-rich dacite to rhyodacite Chilean lava domes will be measured for their bulk chemistry, density, heat capacity, thermal diffusivity, and viscosity. Preliminary heat capacity measured from 50 – 550˚C, values range from 824 to 1054 Jkg^-1K^-1. Preliminary thermal diffusivities measured from 25 to 500˚C, values range from  0.55 to 0.31 mm²s^-1. Bulk densities for the Chilean domes range from 1980 to 2300 kgm^-3. For temperature from 850 - 1000˚C and strain rates of about 10^-6s^-1, the Chilean lavas have high viscosity ranging from 10¹⁰ to 10¹² Pas. Previous sample analysis and an existing viscosity model based on Obsidian Dome will provide crystal-poor silicic composition data. When the Chilean domes are compared with Obsidian dome and an andesitic-dacite lava from Santiaguito, they behave most similarly to the Santiaguito lava. The measured laboratory properties will be used along with various effusion rates in a thermo-rheological model to constrain the emplacement conditions for these non-channelized, axisymmetric torta domes. The model will be implemented through COMSOL Multiphysics with adjustable boundary conditions to allow for various surface conditions (e.g., gravity, atmospheric conditions, surface temperature, etc.) so the model could be applied to lava domes on other planetary bodies, such as the Venusian pancake domes. The model dome morphologies will be compared to the Chilean domes to determine how well their morphology is reproduced. The goal of this research is to constrain the emplacement conditions that allow for the formation of this axisymmetric, flat-topped, steep-sided dome morphology.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

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