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Volcano dome growth, collapse and coupled processes

Periodic Reporting for period 3 - VOLCAPSE (Volcano dome growth, collapse and coupled processes )

Reporting period: 2018-09-01 to 2020-02-29

The growth and collapse of volcanoes is most dynamic at dome-building volcanoes. Volcanic eruptions at most of these volcanoes are traditionally interpreted to be triggered by deep-seated processes that operate chiefly within magma reservoirs or the conduit(s). However, within the VOLCAPSE consolidator project evidence is mounting that many different types of external forcing mechanisms play a significant to dominant role in triggering volcanic eruptions, especially at the dome-building volcanoes. These factors include: (a) dynamic or static stress changes caused by e.g. earthquakes, (b) topographic variations, (c) interaction with groundwater or meteorological factors, and (d) internal structure of a volcanic edifice. These factors are being evaluated in the VOLCAPSE project in great detail. The innovative element of the project is to simultaneously monitor slow and fast ground motions by combining satellite radar data with ground based webcam arrays situated around a volcano. Both data together allow displacement measurements on multiple temporal and spatial dimensions, covering the rates of motion expected at most dome building volcanoes.
We designed prototype time-lapse camera systems that were placed surrounding our target volcanoes. Important here was the use and comparison of different camera qualities, from webcams to high resolution DSLR cameras with intervalometers. These cameras were also synchronized with satellite radar observations from the TerraSAR-X satellite, allowing a view day and night, even through thick volcano eruption plumes. The target volcanoes initially proposed (Colima, Popocatepetl, Chaiten, Lascar, Montserrat, Merapi) were in general very well selected; only the Montserrat case had to be exchanged due to low activity so that we introduce Bezymianny volcano in Kamchatka (which became active in 2016-2017).
Time-lapse camera systems were placed surrounding active target volcanoes and were also synchronized with satellite radar observations from the TerraSAR-X satellite. The multi-dimensional data is allowing a view day and night, even through thick volcano eruption plumes and at high resolution. The target volcanoes initially proposed (Colima, Popocatepetl, Chaiten, Lascar, Bezymianny, Merapi) were visited and measurements realized in the field. Deformation data, changes in camera image features, and tracking of moving objects allowd the study of dome growth, its collapse and the early stages of hazardeous pyroclastic flows. PhD student training was further supported by joint supervision and media training that allows improving communicating results to news/press and television.
Within the VOLCAPSE consolidator project evidence is mounting that many different types of external forcing mechanisms play a significant to dominant role in triggering volcanic eruptions, especially at the dome-building volcanoes. These factors include: (a) dynamic or static stress changes caused by e.g. earthquakes, (b) topographic variations, (c) interaction with groundwater or meteorological factors, and (d) internal structure of a volcanic edifice. The innovative element of the project is to simultaneously monitor slow and fast ground motions by combining satellite radar data with ground based webcam arrays situated around a volcano. Both data together allow displacement measurements on multiple temporal and spatial dimensions, covering the rates of motion expected at most dome building volcanoes.
We designed prototype time-lapse camera systems that were placed surrounding our target volcanoes. Important here was the use and comparison of different camera qualities, from webcams to high resolution DSLR cameras with intervalometers. These cameras were also synchronized with satellite radar observations from the TerraSAR-X satellite, allowing a view day and night, even through thick volcano eruption plumes.
Significant progress has been made related to the following science questions outlined in the original research:

(i) How do dome displacements affect the further magma extrusion position and rates thereafter and how stress changes at the conduit wall develop? Stress changes may have a major effect on the timing and form of eruptions. This question we address currently at two sites that are ideally suited for this analysis (Bezymianny and Colima). At these two sites we could realize ideal configurations of instrument networks, and both sites have shown eruptive activity from 2015 to 2017. Results indicate that the development and directivity of domes can be better understood if the conduit stress conditions are investigated.

(ii) How do large morphology changes in the volcano summit affect dome growth by topographic loading or unloading reaching deeper levels? This question is aiming to tackle an observation that has been out there since decades or even centuries, namely that loading and unloading at deeper levels are caused by volcano summit changes. To investigate this question, we study photogrammetric data and satellite radar data and determine geomorphological changes caused by summit process. Although this study is not conclusive yet, it appears that the effects at depths within the edifice are large, but then diminish rapidly at depth larger 1 km beneath the summit. Here, especially through numerical models, we could find that the topographic effects are highly significant for directing the path of magma or leading to arrest of an intrusion.

(iii) How dome growth is affected by extrinsic triggers such as tectonic quakes, heavy rainfall or other? This question was addressed by a number of our case studies and published in several articles, showing that dome growth intensifies after earthquakes, that domes may fracture following earthquakes and that this fracture follows preferred trend lines, and that some of the explosions follow heavy rainfall episodes. Moreover, as rainfall percolates and accumulates at low altitude regions of the dome, precise morphologic mapping even allows identifying the locations of coming steam driven explosions.

(iv) How relevant are overlapping displacement processes such as cooling (contraction), extrusion and gravity driven deformation in the overall morphometric evolution of the volcano? The complexity of displacement patterns is found to be evident and increasing with higher quality data. A case study realized at an arid volcano, Lascar in Chile, allowed generation of a large number of datasets that are not obscured by environmental limits and poor visibility. We generated over 2000 satellite radar interferograms and found that deformation processes involve cooling, thermal contraction, sagging, and gravity sliding. While it is not sure yet whether this overlapping displacement complexity can equally be found at volcanoes elsewhere, this study demonstrates that our previous picture of deforming volcano summits might have been too simplicity.

Until the end of the project the shallow interactions between developing domes, their surface geomorphology and the basin in which the domes have formed are be investigated in great detail. Furthermore, time lapse camera systems and image analyzing software technologies developed within the course of this project will be transferred by application in the ERC Proof of Concept Grant ((Proposal number: SEP-210510523). The POC proposal will be resubmitted again early 2019.
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