Publication Date:
2022-02-25
Description:
Most basaltic explosive eruptions intensify abruptly, allowing little time to document
processes at the start of eruption. One opportunity came with the initiation of activity from fissure 8 (F8)
during the 2018 eruption on the lower East Rift Zone of Kīlauea, Hawaii. F8 erupted in four episodes.
We recorded 28 min of high-definition video during a 51-min period, capturing the onset of the second
episode on 5 May. From the videos, we were able to analyze the following in-flight parameters: frequency
and duration of explosions; ejecta heights; pyroclast exit velocities; in-flight total mass and estimated mass
eruption rates; and the in-flight total grain size distributions. The videos record a transition from initial
pulsating outgassing, via spaced, but increasingly rapid, discrete explosions, to quasisustained, unsteady
fountaining. This transition accompanied waxing intensity (mass flux) of the F8 eruption. We infer that all
activity was driven by a combination of the ascent of a coupled mixture of small bubbles and melt, and the
buoyant rise of decoupled gas slugs and/or pockets. The balance between these two types of concurrent
flow determined the exact form of the eruptive activity at any point in time, and changes to their relative
contributions drove the transition we observed at early F8. Qualitative observations of other Hawaiian
fountains at Kīlauea suggest that this physical model may apply more generally. This study demonstrates
the value of in-flight parameters derived from high-resolution videos, which offer a rapid and highly timesensitive
alternative to measurements based on sampling of deposits posteruption.
Description:
Published
Description:
e2020JB020903
Description:
5V. Processi eruttivi e post-eruttivi
Description:
JCR Journal
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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