Multidisciplinary insights into the duration of volcanic eruption

Abstract:

Identifying the durations of volcanic eruptions is fundamentally important to understanding volcanic eruptions and the hazards they pose. However, we lack a synoptic description of eruption durations and their relations to other observable parameters, such as eruption style and other timescales. Here, we investigate this topic by compiling data from the Smithsonian’s Global Volcanism Program (GVP) and the Volcanic Ash Advisory Centers (VAACs). Of the ~11000 eruptions in the GVP database, ~3400 confirmed eruptions have known durations. Durations are distributed about 2 peaks: a peak at durations of <1 week (~25% of eruptions) and a second peak at durations between 1 month and 1 year (~40%). More explosive eruptions (i.e., higher VEI) have longer durations, with median durations increasing from ~20 days for eruptions with VEIs of 0–1 to ~100 days for those with VEIs of ≥3. Eruptions of mafic magmas have shorter durations (median of 40 days) than eruptions of more evolved material (230 days for intermediate, 160 days for felsic). These data show no relationship between duration and repose interval. We compare eruption duration with a compilation of run-up durations determined petrologically (crystal clocks) and seismically. Most crystal clocks indicate run-up durations of 1 month to 1 year, broadly comparable to eruption durations. Durations from seismology are similar to those from petrology, but they tend to be shorter, particularly for basaltic eruptions. The ~60000 VAAC reports we analyzed indicate that ash observations are most common at the start of eruptions, consistent with a tendency for early explosive activity. However, as eruptions progress, the overall decrease in the observations of ash is small and variability in the timing of ash observations between individual eruptions is significant, suggesting systematic change in eruptive style is minor. These data will lead to better understanding of the variability and controls over eruption duration.