Explosive Eruptions With Little Warning: Experimental Petrology and Volcano Monitoring Observations From the 2014 Eruption of Kelud, Indonesia

Abstract

Explosive eruptions that occur with little or no precursory unrest (less than a month) pose the greatest hazards from volcanoes to nearby populations. Here we focus on the preeruptive conditions for these explosive events, their triggers and how these eruptions evolve. We concentrate on Kelud volcano, where we have conducted a set of petrological experiments to understand preeruptive storage conditions for several recent eruptions. For the 2014 explosive eruption, we combine this with an analysis of interferometric synthetic aperture radar measured deformation. Our data suggest that both explosive and effusive eruptions at Kelud are sourced from a magma storage system at 2–4 km. However, explosive eruptions are fed by magma stored under relatively cool (~1000 °C) and water‐saturated conditions, whereas effusive eruptions are fed by slightly hotter (~1050 °C), water‐undersaturated magmas. We propose that the initial phase of the 2014 eruption was triggered by volatile overpressure, which then fostered top‐down decompression tapping discrete magma bodies. By compiling a global data set of monitoring signatures of explosive eruptions, we show that the onset of unrest rarely points to the shallow ascent of magma to the surface, as ascent mostly occurs in a matter of hours or minutes. We relate the timescale of preeruptive unrest to eruption triggering mechanisms, with yearly/decadal periods of unrest relating to magma injection events (which may or may not precede a magmatic eruption), whereas internal triggering (e.g., second boiling) of an already present, cooling magma body can lead to explosive eruptions with little warning.

Petrological and monitoring insights into the mechanisms driving eruptions of Kelud volcano, Indonesia

“…% water in the melt. These temperatures are also consistent with the estimates of Cassidy et al (2019 Mineral-melt equilibria data indicates that the melt could have contained up to 3-4 wt. % dissolved water, which is high enough to stabilize amphibole in a range of typical arc compositions (Costa et al, 2013;Sisson & Grove, 1993).…”

“…For example, before the event in 2014, volcano-tectonic earthquakes abruptly spiked starting from 3 rd February, dissipating until 10 February, before a final spike in seismicity occurred a couple of hours before the eruption at 22:50 on 13 February (e.g. Cassidy et al, 2019;Hidayati et al, 2018;Maeno et al, 2016). Such a pattern is observed at other subduction zone volcanoes in the world , and references therein) such as Calbuco volcano in Chile, which erupted explosively in 2015, and had very short run up times of seismicity a few hours before its first explosive phase that produced a volcanic cloud column > 20 km tall Morgado et al, 2019aMorgado et al, , 2019bPardini et al, 2018).…”

Insights into the recurrent energetic eruptions that drive Awu, among the deadliest volcanoes on Earth

“…But the vigorous explosion never happened as suspected (Hidayati et al, 2009). Only 7 years later, in 2014 a VEI 4 eruption was witnessed at the same volcano (Kristiansen et al, 2015;Caudron et al, 2015). Such a delay between dome occurrence through a crater lake and a major eruption was also witnessed on Awu in 1966 when a VEI 4 event occurred 35 years after the lava dome emplacement (in 1931).…”

“…The process can lead to powerful eruptive discharge that can possibly clear out the conduit plug and the lava dome. This was the mechanism that pulverized the lava dome at Kelud in 2014 (Cassidy et al, 2019) and pumped out the degassed magma on Rokatenda in 2012-2013 (Primulyana et al, 2017). Another mechanism that can possibly induce eruption on Awu, given the predominant hydrothermal manifestation, is the acidic-sulfate alteration (Heap et al, 2019).…”

The Christmas 2018 Eruption at Mount Etna: Enlightening How the Volcano Factory Works Through a Multiparametric Inspection

“…Definitely, cutting-edge polyhedral views of volcanic processes can be only conceived through merging of manifold disciplines (e.g., Fernández et al, 2017). Encouraging researches with this rationale have been already launched at some volcanoes on Earth, especially where products of the eruptive activity can be contextualized within the framework of data coming from high-quality monitoring networks (e.g., Carey et al, 2015;Cassidy et al, 2019;Geiger et al, 2016;Hibert et al, 2015;Magee et al, 2018;Martí et al, 2013).…”