Pinpointing magma processes in time and space

Abstract

Volcanic eruptions pose major threats to society, including loss of human life, negative economic impacts, and environmental ramifications. As the global population continues to grow, so does the amount of people living in proximity to volcanoes. Volcanic eruptions are often triggered by perturbations in the magmatic system, which are caused by a variety of magmatic processes, such as magma recharge, magma ascent, and magma mingling. We applied diffusion chronometry, the technique of modeling chemical diffusion across mineral zones, to the 2009 eruption of Redoubt, and the 2016-2017 eruption of Bogoslof, in order to determine and date the pre- and syn-eruptive magmatic processes that triggered and drove the recent eruptions of these two, high-threat, Alaskan volcanoes. At Redoubt, our results, combined with multidisciplinary observations preceding the 2009 eruption, indicate that Redoubt experienced protracted magma recharge between the 1989-1990 and 2009 eruptions, with notably drastic increases in monitoring parameters occurring 3-4 months before the 2009 eruption. At Bogoslof, we analyze both the first and final products from the 9-month long 2016-2017 eruption. Analyses of the early products indicate that pre- eruptive magma recharge occurred in the weeks to months before eruption onset. This interpretation is supported by the seismic swarm that occurred approximately two months before the eruption began. Conversely, our analyses of the final erupted products of Bogoslof reveal that the distinct boundaries in mineral phases formed due to magma decompression caused by the shallow emplacement of magma occurring throughout the second phase of the eruption. The oldest crystal timescales from the second eruptive phase correspond to March 2017, correlating with increases in both seismicity and SO2 emissions. By determining and pinpointing the magma processes associated with volcanic eruptions in time and space, we gain insights into the pre- and syn-eruptive nature of the magma system. Our results aid in interpreting interdisciplinary monitoring data, and contribute to the development of new eruption forecasting tools.