Dyke intrusion between neighbouring arc volcanoes responsible for 2017 pre-eruptive seismic swarm at Agung

Using seismic data and numerical modelling, here, the authors characterize the three-month period of unrest occurring prior to the 2017 Agung eruption (Bali, Indonesia). They observe a large uplift signal located at ~5 km from Agung summit corresponding to the emplacement of a 10 km deep magma intrusion between Agung edifice and Batur caldera, suggesting a potential magmatic connection between the two volcanic systems

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

International audienceAbstract. The little-known Awu volcano (Sangihe Islands, Indonesia) is among the deadliest, with a cumulative death toll of 11 048. In less than 4 centuries, 18 eruptions were recorded, including two VEI 4 and three VEI 3 eruptions with worldwide impacts. The regional geodynamic setting is controlled by a divergent-double-subduction collision and an arc–arc collision. In that context, the slab stalls in the mantle, undergoes an increase in temperature, and becomes prone to melting, a process that sustained the magmatic supply. Awu also has the particularity of hosting alternatively and simultaneously a lava dome and a crater lake throughout its activity. The lava dome passively erupted through the crater lake and induced strong water evaporation from the crater. A conduit plug associated with this dome emplacement subsequently channeled the gas emission to the crater wall. However, with the lava dome cooling, the high annual rainfall eventually reconstituted the crater lake and created a hazardous situation on Awu. Indeed with a new magma injection, rapid pressure buildup may pulverize the conduit plug and the lava dome, allowing lake water injection and subsequent explosive water–magma interaction. The past vigorous eruptions are likely induced by these phenomena, possible scenarios for future events

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

The little-known Awu volcano (Sangihe Islands, Indonesia) is among the deadliest, with a cumulative death toll of 11 048. In less than 4 centuries, 18 eruptions were recorded, including two VEI 4 and three VEI 3 eruptions with worldwide impacts. The regional geodynamic setting is controlled by a divergent-double-subduction collision and an arc-arc collision. In that context, the slab stalls in the mantle, undergoes an increase in temperature, and becomes prone to melting, a process that sustained the magmatic supply. Awu also has the particularity of hosting alternatively and simultaneously a lava dome and a crater lake throughout its activity. The lava dome passively erupted through the crater lake and induced strong water evaporation from the crater. A conduit plug associated with this dome emplacement subsequently channeled the gas emission to the crater wall. However, with the lava dome cooling, the high annual rainfall eventually reconstituted the crater lake and created a hazardous situation on Awu. Indeed with a new magma injection, rapid pressure buildup may pulverize the conduit plug and the lava dome, allowing lake water injection and subsequent explosive water-magma interaction. The past vigorous eruptions are likely induced by these phenomena, possible scenarios for future events

Post-Eruption Lava Dome Emplacement Measured by UAV Photogrammetry: An Investigation One Year After The 2017-2019 MT. Agung Eruptions

We present an observation of morphological changes at Mt. Agung lava dome one year after the 2017-2019 eruption crisis using UAV-photogrammetry method. Five time-series UAV datasets involve the images collected during the crisis period and the newest data collection (July 16, 2020) were used to provide a detailed investigation of the changes in morphology inside the crater and land cover on the surrounding slopes. The digital surface models (DSMs) generated by structure-from-motion (SfM) with multi-view stereo (MVS) algorithm were used to quantify the dome growth, the surface emplacement, and the actual remaining deposited material eruption surrounding the summit. Analysis of the last two series orthoimages indicates that the crater surface's texture remarkably unchanged one year after the eruption crisis (the dome still presents rough surfaces that resemble small stones and sand). According to the DSMs difference, it is evident that there were no considerable surface displacements inside the dome. It implies that no significant magma pressure accumulation occurring the dome. However, we found a small-scale growth in the central dome, which has increased the dome height up to 2 m and inflate the dome with a volume of 45,950 m3. We have also observed a new lava lake (e.g., compound lava) with an area of 9,166 m2 in the southeast of the dome edge. This new lava lake uplifts the surface up to 29 m and translated to a 79,623 m3 additional volume. Meanwhile, the depression areas surrounding the central dome were observed with a depth between 0.5 and 4 m. The amount of material deposited on the volcano's summit was identified with a total volume of 2.93 × 106 m3. This remaining deposited volume could be a potential lahar in the future. The ability to measure spatial and time-series of the lava dome changes from SfM-UAV, therefore, provides effective, detailed, and sometimes sole means of observing and quantifying dome surface emplacement in the period of before, during and after eruptions. © 2022. International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives. All rights reserved