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Abstract:
Episodes of detectable unrest (e.g., seismicity, deformation, degassing and thermal anomalies) are known to precede the onset of volcanic eruptions. However, on decadal timescales, many volcanoes also exhibit phases of unrest that are not immediately preceded or followed by eruption. According to information in the Smithsonian Institution’s Global Volcanism Program (GVP) reports and database, 427 volcanoes worldwide experienced some combination of unrest and eruption between 2000-2022. Using a structured qualitative coding approach, I classify over 4000 volcano-specific GVP reports and databases as ‘questionable unrest’, ‘unrest’, or ‘eruption’ and use these to develop decadal-scale timelines for all 427 volcanoes. The resulting timelines indicates the overall proportions of volcanoes that experienced (a) only non-eruptive unrest, (b) only eruption, and (c) some combination thereof, and confirm earlier studies indicating that over 50% of unrest episodes do not immediately culminate in an eruption. Further analysis of the 168 volcanoes that experienced both documented unrest and eruption during the study period suggests relationships between the relative timing of pre-eruption unrest (whether it is temporally discrete from or immediately precursory to eruption) and the explosivity (characterized by VEI) and duration of ensuing eruptions. Most notably, over half of recent large (VEI 4-5) eruptions were preceded by discrete episodes of unrest and/or minor eruption in the years prior to the onset of precursory unrest and/or major eruption. Results of this analysis may become useful as a basis for using a volcano’s history of non-eruptive unrest to forecast the intensity and duration of its future eruptions.
