Using numerical modeling to explore the origin of intrusion patterns on Fernandina volcano, Galapagos Islands, Ecuador

Abstract

Using parameterized finite element models, we investigate the emplacement of both radial and circumferential intrusions in the configuration observed at Fernandina volcano in the Galapagos Islands. When situated within the edifice at depths consistent with petrological and surface displacement data, inflation of a mildly oblate magma reservoir to the point of rupture can initiate either radial or circumferential intrusions in response to minor, volcanologically plausible variations in reservoir geometry (i.e., aspect ratio). In addition, more oblate reservoirs inject lateral sills into an inflation-derived stress field consistent with rotation about their propagation axis to form gently dipping radial dikes, a mode of behavior recently inferred from InSAR data at Fernandina. All three styles of intrusion occur in near-surface configurations consistent with field observations. Key Points Reservoir depth and geometry affect edifice stress state and intrusion geometry Radially oriented dikes can initiate directly from a shallow oblate reservoir We can match intrusion geometries observed on Galapagos Island volcanoes ©2013. American Geophysical Union. All Rights Reserved.