Constraining the Thermal History of Hayrick Butte, a Subglacial Volcano in the Oregon Cascades

Subglacial volcanism has been documented in Antarctica, Iceland, British Columbia, and the Pacific Coast of North and South America. Though widespread, the interactions between magma and ice during these eruptions are not thoroughly understood. Detecting subglacial eruptions and mitigating the associated hazards rely on understanding heat transfer between magma and ice, the formation of ice cauldrons, and the ensuing meltwater production. Although some physics-based models exist for subglacial eruptions, most of these are not well constrained with field evidence. To address this, we are studying Hayrick Butte, a 0.2-km-tall, 0.8-km-wide basaltic andesite tuya located 20 miles west of Sisters, OR, in the Oregon Cascades range. The butte's steep sides, flat top, and anomalous thickness suggest the dome was erupted subglacially. In addition to its overall flat-topped geometry, Hayrick Butte contains cooling joints of varying thicknesses and orientations, suggesting rates of cooling that vary spatially around the butte. We use drone imagery to create a 3D structure-from-motion model to map the spatial distribution of the cooling columns. We compare these with crystal size distribution to determine how the relative cooling rate varies with the differing column geometries. The results from this fieldwork will ultimately be used to constrain a physics-based numerical model for the formation of the butte. By constraining the cooling history of this tuya, we will gain a better understanding of the distribution and rate of heat exchange in ice-magma interactions, and what influences the geometry and size of cooling joints, which has implications for interpreting magma-water interactions more generally.