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Modeling the Effects of Ice and Volcanic Cone Loading on Dike Propagation in Arc Settings: Implications for Mocho-Choshuenco Volcano, Chile

Meredith Townsend 1, Pablo Moreno-Yaeger2, Andrew Harp3, Christian Huber4, Brad S. Singer2

  • Affiliations:  1Department of Earth and Environmental Sciences, Lehigh University; 2Department of Geoscience, University of Wisconsin-Madison; 3Department of Earth and Environmental Sciences, California State University Chico; 4Department of Earth and Planetary Sciences, Brown University 

  • Presentation type: Poster

  • Presentation time: Monday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 183

  • Programme No: 3.3.17

  • Theme 3 > Session 3

Abstract

The response of magmatic systems to ice loading in continental arc settings is shaped by shallow crustal stress changes, which are influenced by volcanic topography and ice distribution. We develop a model that integrates crustal stress calculations under glaciated stratovolcanoes with a model for dike propagation that accounts for stresses induced by both volcano and ice loads. Our model incorporates spatial variations in ice thickness influenced by volcanic topography. Applying this framework to the southern Andean Volcanic Zone, where stratovolcanoes were capped by the ~2-km-thick Patagonian Ice Sheet (PIS) during the Last Glacial Maximum (LGM), we find that the weight of the volcanic edifice is a greater barrier to dike ascent than the ice sheet itself. However, ice loads introduce a "pinching point" of concentrated compressive stress beneath a volcano, where dikes ascending from below are more likely to stall, while those initiated above this point are squeezed upward. Model results suggest that ice loading could paradoxically facilitate shallow dike ascent while hindering deeper magma transport, a hypothesis we explore using new thermobarometry data from Mocho-Choshuenco Volcano, Chile. These data reveal a deepening of mafic magma source depths by ~3 km during the LGM, accompanied by increased magma differentiation to form silicic reservoirs that erupted after the ice disappeared. These changes could be explained by dikes stalling at greater depths during the peak of the PIS, cutting off recharge to shallower magma reservoirs while promoting recharge at deeper levels, providing a mechanistic basis for observed links between glaciation and volcanism.