Publication Date:
2020-12-21
Description:
Pulsatory eruptions are marked by a sequence of explosions which can be
separated by time intervals ranging from a few seconds to several hours.
The quantification of the periodicities associated with these eruptions
is essential not only for the comprehension of the mechanisms
controlling explosivity, but also for classification purposes. We focus
on the dynamics of pulsatory activity and quantify unsteadiness based on
the distribution of the repose time intervals between single explosive
events in relation to magma properties and eruptive styles. A broad
range of pulsatory eruption styles are considered, including
Strombolian, violent Strombolian and Vulcanian explosions. We find a
general relationship between the median of the observed repose times in
eruptive sequences and the viscosity of magma given by eta approximate
to 100.t(median). This relationship applies to the complete range of
magma viscosities considered in our study (10(2) to 10(9) Pas)
regardless of the eruption length, eruptive style and associated plume
heights, suggesting that viscosity is the main magma property
controlling eruption periodicity. Furthermore, the analysis of the
explosive sequences in terms of failure time through statistical
survival analysis provides further information: dynamics of pulsatory
activity can be successfully described in terms of frequency and
regularity of the explosions, quantified based on the log-logistic
distribution. A linear relationship is identified between the
log-logistic parameters, mu and s. This relationship is useful for
quantifying differences among eruptive styles from very frequent and
regular mafic events (Strombolian activity) to more sporadic and
irregular Vulcanian explosions in silicic systems. The time scale
controlled by the parameter mu, as a function of the median of the
distribution, can be therefore correlated with the viscosity of magmas;
while the complexity of the erupting system, including magma rise rate,
degassing and fragmentation efficiency, can be also described based on
the log-logistic parameter s, which is found to increase from regular
mafic systems to highly variable silicic systems. These results suggest
that the periodicity of explosions, quantified in terms of the
distribution of repose times, can give fundamental information about the
system dynamics and change regularly across eruptive styles (i.e.,
Strombolian to Vulcanian), allowing for direct comparison and
quantification of different types of pulsatory activity during these
eruptions. (C) 2016 Elsevier B.V. All rights reserved.
Description:
Published
Description:
160-168
Description:
3V. Dinamiche e scenari eruttivi
Description:
JCR Journal
Description:
restricted
Keywords:
explosions pulsatory activity magma viscosity repose interval source dynamics eruptive style
;
04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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