Search for: All records

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 The intrusion of magma into Kīlauea's lower East Rift Zone in May 2018 led to the largest eruption along this segment of the volcano in over 200 years. As magma drained from the rift zone, leading to the collapse of Pu'u ‘Ō‘ō, pressure at the summit initially remained elevated and dropped at a slower rate compared to historical intrusion events. The anomalously long timescale of summit deflation suggests that the dike was fed from multiple sources. Here we show that dikes can serve as “dipsticks” of magma reservoirs and that the co‐evolution of dike growth and reservoir deflation constrains key magma transport parameters. Using coupled dike‐chamber models constrained by ground deformation and seismicity, we test four configurations of magma plumbing in order to illuminate which reservoirs and transport pathways were activated during the intrusion phase (30 April to 3 May) of the 2018 event. Slow summit deflation relative to the rate of dike propagation is best explained by a model in which the dike initiates from a compressible magma reservoir in the East Rift Zone, which then drains magma upstream from the Halema'uma'u reservoir through a shallow transport system. We use a Bayesian Markov chain Monte Carlo (MCMC) approach to estimate storage parameters for both reservoirs as well as the effective conductivity of the shallow magma transport system in the East Rift Zone, finding good agreement with independent estimates. Our results suggest that the rupture of reservoirs from within the East Rift Zone presents a unique hazard at Kīlauea. 

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. 

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 Crustal magma chambers can grow to be hundreds to thousands of cubic kilometers, potentially feeding catastrophic caldera‐forming eruptions. Smaller volume chambers are expected to erupt frequently and freeze quickly; a major outstanding question is how magma chambers ever grow to the sizes required to sustain the largest eruptions on Earth. We use a thermo‐mechanical model to investigate the primary factors that govern the extrusive:intrusive ratio in a chamber, and how this relates to eruption frequency, eruption size, and long‐term chamber growth. The model consists of three fundamental timescales: the magma injection timescaleτ_in, the cooling timescaleτ_cool, and the timescale for viscous relaxation of the crustτ_relax. We estimate these timescales using geologic and geophysical data from four volcanoes (Laguna del Maule, Campi Flegrei, Santorini, and Aso) to compare them with the model. In each of these systems,τ_inis much shorter thanτ_cooland slightly shorter thanτ_relax, conditions that in the model are associated with efficient chamber growth and simultaneous eruption. In addition, the model suggests that the magma chambers underlying these volcanoes are growing at rates between ~10⁻⁴and 10⁻² km³/year, speeding up over time as the chamber volume increases. We find scaling relationships for eruption frequency and size that suggest that as chambers grow and volatiles exsolve, eruption frequency decreases but eruption size increases. These scaling relationships provide a good match to the eruptive history from the natural systems, suggesting that the relationships can be used to constrain chamber growth rates and volatile saturation state from the eruptive history alone.