7158 20241214122733.0 10.1029/2024JB029568 DOI SCART-2024-0191 Yates, A.S. Seasonal Snow Cycles and Their Possible Influence on Seismic Velocity Changes and Eruptive Activity at Ruapehu Volcano, New Zealand 2024 Understanding volcanic eruption triggers is critical toward anticipating future activity. While internal magma dynamics typically receive more attention, the influence of external processes remains less understood. In this context, we explore the relationship between seasonal snow cycles and eruptive activity at Ruapehu, New Zealand. This is motivated by apparent seasonality in the eruptive record, where a higher than expected proportion of eruptions (post-1960) occur in spring (including the two previous eruptions of 2006 and 2007). Employing recent advancements in passive seismic interferometry, we compute sub-surface seismic velocity changes between 2005 and 2009 using the cross-wavelet transform approach. Stations on the volcano record a higher velocity in winter, closely correlated with the presence of snow. Inverting for depth suggests these changes occur within the upper 300 m. Notably, we observe that the timing of the previous two eruptions coincides with a period associated with an earlier velocity decrease at approximately 200–300 m depth relative to the surface. Reduced water infiltration (as precipitation falls as snow) is considered a likely control of seasonal velocities, while modeling also points to a contribution from snow-loading. We hypothesize that this latter process may play a role toward explaining seasonality in the eruptive record. Our findings shed light on the complex interactions between volcanoes and external environmental processes, highlighting the need for more focused research in this area. Pursuing this line of inquiry has significant implications toward improved risk and hazard assessments at not just Ruapehu, but also other volcanoes globally that experience seasonal snow cover. NO volcanoseismology ambient noise velocity variations monitoring environmental seismology Caudron, C. Mordret, A. Lesage, P. Pinel, V. Lecocq, T. Miller, C.A. Lamb, O.D. Fournier, N Journal of Geophysical Research: Solid Earth 129 2024 e2024JB029568 thomas.lecocq@ksb-orb.be http://github.com/ROBelgium/MSNoise https://github.com/covseisnet/covseisnet https://github.com/regeirk/pycwt 513932 http://publi2-as.oma.be/record/7158/files/jgrb57063-fig-0010-m.jpg Conceptual model of possible unloading-induced degassing process related to loading/unloading of a snow-load. (a) Pre-winter (e.g., January–May): minimal snow-load present on the volcano. (b) Early winter (e.g., June–July): snow-load begins to accumulate, inducing a positive pressure change. (c) Late-winter (e.g., July–September): maximum snow-load present on the volcano. (d) Spring (e.g., September–November): snow-load begins to melt, with pressures decreasing in the subsurface. 11625 http://publi2-as.oma.be/record/7158/files/jgrb57063-fig-0010-m.gif?subformat=icon icon Conceptual model of possible unloading-induced degassing process related to loading/unloading of a snow-load. (a) Pre-winter (e.g., January–May): minimal snow-load present on the volcano. (b) Early winter (e.g., June–July): snow-load begins to accumulate, inducing a positive pressure change. (c) Late-winter (e.g., July–September): maximum snow-load present on the volcano. (d) Spring (e.g., September–November): snow-load begins to melt, with pressures decreasing in the subsurface. 13422 http://publi2-as.oma.be/record/7158/files/jgrb57063-fig-0010-m.jpg?subformat=icon-180 icon-180 Conceptual model of possible unloading-induced degassing process related to loading/unloading of a snow-load. (a) Pre-winter (e.g., January–May): minimal snow-load present on the volcano. (b) Early winter (e.g., June–July): snow-load begins to accumulate, inducing a positive pressure change. (c) Late-winter (e.g., July–September): maximum snow-load present on the volcano. (d) Spring (e.g., September–November): snow-load begins to melt, with pressures decreasing in the subsurface. published in REFERD