Promoting Basal Slide and Flank Eruptions due to Edifice Relaxation in the Mauna Loa-Kīlauea Volcanic System, Hawaiʻi

Abstract:

Classically, volcanic eruptions are thought to initiate through a centralized vent; however, eruptions can also occur on the flanks of volcanoes. The mechanisms for triggering flank eruptions remain an outstanding complication when forecasting volcanic eruptions—a field of knowledge essential for warning the millions of people that currently reside along these flanks. Kīlauea Volcano’s 2018 eruption along its Lower East Rift Zone indicates the potential connection between slip along the Big Island’s décollement and triggering of large eruptions along the flanks of Kīlauea Volcano. Geophysical observations (e.g., seismicity and geodesy) recorded during the 2018 eruption provide important clues into the initiation and evolution of flank eruptions. It remains unclear how the timing of flank eruptions is influenced by the competing interactions of magma pressure and viscoelastic relaxation of the Mauna Loa-Kīlauea edifices. In this investigation, we utilize finite element models to investigate the stress evolution of a large volcanic edifice and its influence on the stability and eruption potential of its magma system. Numerical experiments test how edifice relaxation impacts the potential location of radial diking and flank eruptions, as well as the potential for initiating slip along the basal décollement. Preliminary results suggest that dikes initiating in the edifice will radiate away from the magma chamber and down the flanks of the volcanoes, regardless of whether or not the edifice is in isostatic equilibrium. However, models in which the edifice is not equilibrated indicate the dikes must propagate further down flank prior to eruption. Model results generally agree with observations of flank eruptions in the Mauna Loa-Kīlauea system on the Big Island of Hawaiʻi. Additional numerical experiments that incorporate a weak, basal décollement indicate relaxation of the edifice does not promote slip along the basal décollement. Analysis of flank eruptions remains a critical investigation for volcanologists; the use of numerical experiments to deduce the interactions between such elements allow for advanced hazard preparation and encourages accurate forecasts of volcanic eruptivity.