Volcano flank deformation and instability driven by the compaction of clastic deposits

• Applicant: Dr. Edgar Zorn
• Subject Area: Geology ; Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 561282832

Volcanoes are built rapidly from the successive deposition of lavas and pyroclastic materials during effusive and explosive eruptions. The rapid accumulation of heterogeneous volcanic material results in inherently unstable volcanic structures as deposits compact through cooling and gravitational settling. These exert variable stresses and strains due to changes in temperature and loading after their emplacement. These also change the thermal, physical, and mechanical properties of the consolidating deposits and form key controls for the stability of the flank, yet they are not well quantified. The consequences of such instability are varied and may range from small-scale ground deformation and rockfalls causing localized infrastructure damage, to large-scale catastrophic collapse of the volcanic edifices causing debris avalanches and widespread destruction. Past collapses have constituted some of the deadliest volcanic disasters in history and still remain poorly understood and unpredictable today, making it vital to improve our scientific knowledge and hazard assessments for future events. In this proposal I outline a 6-year research plan to outline and quantify the effects of volcaniclastic deposit consolidation on volcano flank deformation and how the changes in thermo-physico-mechanical properties of the deposits affect the stability of volcanic flanks over time. The goal is to provide quantitative datasets and methods to determine and forecast flank instability on volcanoes worldwide, enabling improved hazard assessment, decision making for stakeholders, and infrastructure development planning. This will be successfully achieved in three key objectives; by determining spatio-temporal scales of post-eruptive surface deformation at volcanoes (O1) using satellite remote sensing and field work, by constraining the physical and thermo-mechanical properties of compacting deposits (O2) in novel laboratory experiments, and by bridging field- and lab-scale deformation to predict the stability evolution of volcanoes (O3) using numerical modeling. This will integrate multi-disciplinary observations and data obtained strategically at different scales and allow to form concise assessments of ground deformations, deposit properties and collapse hazards at volcanoes worldwide. The results will enable us to understand and predict the progression of compaction and strength evolution of clastic volcanic deposits, thereby flagging potential weaknesses that may result in future collapses. They present invaluable data for hazard assessments at the affected volcanoes, opening a unique way of addressing otherwise speculative stability problems using our novel testing methods. The successful outcomes will shed light on the driving processes and scales of currently unpredictable volcano flank instability into a scientifically manageable and partially forecastable hazard.

• DFG Programme: Emmy Noether Independent Junior Research Groups
• International Connection: Italy, Spain
• Major Instrumentation: Direct Shear Apparatus
• Instrumentation Group: 2940 Spezielle Baustoff- und Bodenprüfgeräte, Schergeräte
• Cooperation Partners: Dr. Pablo J. Gonzalez; Francesco Maccaferri, Ph.D.