Extreme Curvature of Shallow Magma Pathways Controlled by Competing Stresses: Insights From the 2018 Sierra Negra Eruption

Abstract

Eruptions at shield volcanoes often occur from radially aligned linear fissures fed by blade‐like magma‐filled cracks (dykes). The fissures of the 2018 Sierra Negra eruption were scattered on the flank of the volcano. Space‐borne radar interferometric data (interferometric synthetic aperture radar) revealed that, unexpectedly, part of the eruption was fed by a 15 km long, tortuous and flat‐lying crack (sill). Here we develop a framework that captures the full three‐dimensional (3D) kinematics of non‐planar intrusions. This includes both an analytical and comprehensive numerical scheme. We constrain the models such that they match the observed ground deformation at Sierra Negra. We show that the peculiar sill trajectory is due to the competing stress gradient magnitudes being close to one another throughout its propagation. By accounting for the interaction of all these factors, these 3D models open the possibility to understand and simulate the geometry of magma transport at volcanic systems.

Modeling Dike Propagation in Both Vertical Length and Horizontal Breadth

“…Predicting a dike's path and velocity can give authorities a sense of when and where they will erupt and is therefore of utmost importance for hazards management. This can be accomplished via numerical methods, such as models that focus on quasi‐steady‐state scenarios (e.g., Dahm, 2000; Roper & Lister, 2007) and finite element models, which can be slower to perform, but enable more complex simulations (e.g., Davis et al., 2021; Maccaferri et al., 2011, 2019; Pinel et al., 2017; Zia & Lecampion, 2020). These models are traditionally simplified to a 2D cross section, which propagates along one dimension and inflates in the other, neglecting changes and any associated flow or pressure gradients in the third dimension.…”

“…This is especially true at shallow depth where, depending on the geologic setting, dikes are likely to assume lateral propagation (Horst et al., 2014; Peltier et al., 2005; Townsend et al., 2017). More recently, advances in computing power allow for ever‐more‐complex 3D models capable of simulating different forms of propagation (Davis et al., 2021; Zia & Lecampion, 2020), although such models are computationally expensive.…”

Volcanotectonics: the tectonics and physics of volcanoes and their eruption mechanics

“…1d) during unrest periods (Browning et al 2015) and determination of the likely propagation paths of the resulting intrusions (Figs. 1a and 2; Gudmundsson 2020; Davis et al 2021).…”

Numerical Simulation of Magma Pathways and Vent Distribution in Rifts From the Early Stages to Maturity

“…Davis (2021) extended them to three dimensions approximating the fracture as a penny-shaped crack influenced by both an internal pressure and stress gradients (analytical method) and simulating curved fractures as a mesh of triangular dislocations computed using the displacement discontinuity method (numerical method). They applied the results to propagating dikes and sills in volcanic regions, focusing on reconstructing the trajectory of a large horizontal sill formed during the 2018 Sierra Negra eruption (Davis et al 2021). In addition to involving short computation times, these models can be applied to arbitrary stresses, topographies and crack shapes, therefore proving to be very suitable to extend my simulations to three-dimensional unloading conditions and may serve as an interesting starting point for future works.…”