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Abstract Silicic caldera-forming eruptions are among the most hazardous natural phenomena on Earth, yet their triggering mechanisms remain poorly understood. While volatile exsolution is widely recognized as a potential eruption driver in large silicic systems, we find that volatile resorption can, counterintuitively, promote chamber pressurization faster than volatile exsolution. Using a thermo-mechanical magma chamber model, we show that resorption is a common process in rapidly recharged systems, driven by pressure increase and crystal melting. The Aso-4 eruption offers a natural case where volatile resorption may have occurred, with model results predicting resorption at recharge rates >10^-2.4km³/yr. Through reducing bulk magma compressibility, resorption amplifies pressurization, driving chamber destabilization and potentially expediting eruption onset. Here, we propose that volatile resorption is a natural process both accommodating and promoting rapid chamber pressurization, fundamental to destabilizing large-scale silicic systems. Detecting its signatures in monitoring signals could provide early warning of imminent eruption. 

While the effects of volcanism on Earth’s climate are well understood, the volcano-ice sheet system hosts a two-way feedback. Volcanic activity promotes ice melting, which in turn affects the internal dynamics of the magma chamber below. At present, accurate forecasts of sea-level rise hinge on the stability of the West Antarctic Ice Sheet, and thus require consideration of subglacial volcano-deglaciation feedbacks. The West Antarctic Ice Sheet, grounded below sea-level, is particularly vulnerable to collapse, yet its position atop an active volcanic rift is seldom considered. Ice unloading raises the geotherm and alters the crustal stress field, impacting dike propagation. However, the consequences on internal magma chamber dynamics and thus long-term eruption behavior remain elusive. Given potential for unloading-triggered volcanism in West Antarctica to accelerate ice retreat, we adapt the thermomechanical magma chamber model of Scholz et al. (2023) for West Antarctic Rift basalts, simulating a shrinking ice load through a prescribed decrease of lithostatic pressure. Examining different unloading scenarios, we investigate the impacts on volatile partitioning within the magma and eruptive trajectory across a wide range of initial magma chamber conditions. Pressurization of a magma chamber beyond a critical threshold results in eruption, delivering enthalpy to the ice. Considering the removal of km-thick ice sheets, we demonstrate the rate of unloading is dominant in influencing the cumulative mass erupted and consequently, heat released to the ice. These findings provide fundamental insights into the complex volcano-ice interactions in West Antarctica and other subglacial volcanic settings. 

Abstract Magmatic volatiles drive pressure, temperature, and compositional changes in upper crustal magma chambers and alter the physical properties of stored magmas. Previous studies suggest that magmatic H₂O content influences the growth and longevity of silicic chambers through regulating the size and frequency of eruptions and impacting the crystallinity‐temperature curve. However, there has been comparatively little exploration of how CO₂impacts the evolution of magma chambers despite the strong influence of CO₂on H₂O solubility and the high concentrations of CO₂often present in mafic systems. In this study, we integrate the thermodynamic effects of dissolved and exsolved H₂O and CO₂with the mechanics of open‐system magma chambers that interact thermally and mechanically with the crust. We applied this model to investigate how intrinsic variations in magmatic H₂O‐CO₂content influence the growth and longevity of silicic and mafic magma chambers. Our findings indicate that even with a tenfold increase in CO₂content (up to 10,000 ppm), CO₂plays a minimal role in long‐term chamber growth and longevity. While CO₂content affects the magma compressibility, the resulting changes in eruption mass are balanced out by a commensurate change in eruption frequency so that the time‐averaged eruptive flux and long‐term chamber behavior remain similar. In contrast, H₂O content strongly influences chamber growth and longevity. In silicic systems, high H₂O contents hinder magma chamber growth by increasing the total eruptive flux and steepening the slope of the crystallinity‐temperature curve. In mafic systems, high H₂O contents promote magma chamber growth by flattening the slope of the crystallinity‐temperature curve. 

Abstract Glacial loading and unloading could impact eruptive outputs at mid‐ to high‐latitude arc volcanoes, yet the influence on magma storage conditions remains poorly understood. Mocho‐Choshuenco volcano in the Andean Southern Volcanic Zone has been impacted by the advance and retreat of the Patagonian ice sheet (PIS). We present stratigraphic observations, conceptual and numerical models of ice (un)loading during the most recent glacial‐interglacial cycle, and use mineral‐based thermobarometry and thermodynamic modeling to explore the evolution of the magma plumbing system. Crustal assimilation was evident during glaciation when incompatible element‐rich basaltic andesitic lavas at 26 to 18 ka crystallized at depths of 11–15 km. During this period a >5 km³silicic reservoir began to grow at 10–15 km, similar to the depth of maximum mean stress change by ∼5.5 MPa caused by PIS loading. Volatile exsolution within the reservoir might have generated overpressure that initiated diking and propelled two caldera‐forming, amphibole‐bearing rhyolites at 13.5 and 11.5 ka. We propose that increased compressional stresses associated with ice loading during the Last Glacial Maximum inhibited eruption and promoted growth of the deep silicic reservoir. Explosive eruptions from this reservoir 3–5 kyr following rapid ice unloading likely reflect the interplay of viscous relaxation of crustal wallrocks and delayed, but abrupt, volatile exsolution from rhyolitic melt to generate overpressure and dike formation. This interdisciplinary approach can be applied to other glaciated volcanoes and arcs to examine how ice loading and unloading modulate upper crustal magma fluxes that are governed at greater depths by rates of mantle melting. 

Abstract We present a model for a coupled magma chamber–dike system to investigate the conditions required to initiate volcanic eruptions and to determine what controls the size of eruptions. The model combines the mechanics of dike propagation with internal chamber dynamics including crystallization, volatile exsolution, and the elastic response of the magma and surrounding crust to pressure changes within the chamber. We find three regimes for dike growth and eruptions: (1) below a critical magma chamber size, eruptions are suppressed because chamber pressure drops to lithostatic before a dike reaches the surface; (2) at an intermediate chamber size, the erupted volume is less than the dike volume (“dike-limited” eruption regime); and (3) above a certain chamber size, dikes can easily reach the surface and the erupted volume follows a classic scaling law, which depends on the attributes of the magma chamber (“chamber-limited” eruption regime). The critical chamber volume for an eruption ranges from ∼0.01 km3 to 10 km3 depending on the water content in the magma, depth of the chamber, and initial overpressure. This implies that the first eruptions at a volcano likely are preceded by a protracted history of magma chamber growth at depth, and that the crust above the magma chamber may have trapped several intrusions or “failed eruptions.” Model results can be combined with field observations of erupted volume, pressure, and crystal and volatile content to provide tighter constraints on parameters such as the eruptible chamber size.