Publication Date:
2021-07-13
Description:
Understanding the mechanisms that cause effusive eruptions is the key to mitigating their
associated hazard. Here we combine results from permanent ultraviolet (UV) cameras, and from other
geophysical observations (seismic very long period, thermal, and infrasonic activity), to characterize volcanic
SO2 flux regime in the period prior, during, and after Stromboli’s August–November 2014 effusive eruption.
We show that, in the 2 months prior to effusion onset, the SO2 flux levels are 2 times average level. We explain
this anomalously high SO2 regime as primarily determined by venting of rapidly rising, pressurized SO2-rich
gas pockets produced by strombolian explosions being more frequent and intense than usual. We develop a
procedure to track (and count), in the UV camera record, the SO2 flux pulses produced by individual
explosions and puffing activity (active degassing). We find that these SO2 pulses are far more numerous
(67 ± 47 events per hour) before the effusion onset than during normal activity (20 ± 15 events per hour). This
observation, combined with geophysical evidence, demonstrates an elevated gas bubble supply to the
shallow conduits, causing elevated explosive and puffing activity. This increase (≥0.1 m3 s 1) in magma
transport rate in the north-east feeding conduits finally triggers effusion onset. Active degassing remains
elevated also during the effusive phase, supporting the persistence of explosive and puffing activity during
the effusive eruption, deep in the volcanic conduit. Our results demonstrate that permanent UV cameras can
valuably contribute to monitoring at high-sampling frequency gas dynamics and fluxes, thus opening the
way to direct comparison with more established geophysical observations.
Description:
Published
Description:
4377 – 4394
Description:
5V. Dinamica dei processi eruttivi e post-eruttivi
Description:
JCR Journal
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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