Two early Holocene rock avalanches in the Bernese Alps (Rinderhorn, Switzerland)

Grämiger, Lorenz; Moore, Jeffrey R.; Vockenhuber, Christof; Aaron, Jordan; Hajdas, Irka; Ivy‐Ochs, Susan

doi:10.1016/j.geomorph.2016.06.008

Cited by 39 publications

(30 citation statements)

References 73 publications

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“…On the other hand, prehistoric slope failures in many alpine valleys, last occupied by ice during the LGM, often cannot be connected to deglaciation as a direct trigger. These events frequently reveal large lag times between deglaciation and the timing of failure (Ballantyne et al, 2014;Grämiger et al, 2016;McColl, 2012;Prager et al, 2008). Ice advance and retreat in the main alpine valleys during the last glaciation, in combination with thermo-hydro-mechanical effects and glacial erosion, may have prepared adjacent slopes with favorable predisposition for failure.…”

Section: Comparison Of Preparatory Factors For Paraglacial Rock Slopementioning

confidence: 99%

Hydromechanical Rock Slope Damage During Late Pleistocene and Holocene Glacial Cycles in an Alpine Valley

et al. 2020

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Subglacial water pressures influence groundwater conditions in proximal alpine valley rock slopes, varying with glacier advance and retreat in parallel with changing ice thickness. Fluctuating groundwater pressures in turn increase or reduce effective joint normal stresses, affecting the yield strength of discontinuities. Here we extend simplified assumptions of glacial debuttressing to investigate how glacier loading cycles together with changing groundwater pressures generate rock slope damage and prepare future slope instabilities. Using hydromechanical coupled numerical models closely based on the Aletsch Glacier valley in Switzerland, we simulate Late Pleistocene and Holocene glacier loading cycles including long‐term and annual groundwater fluctuations. Measurements of transient subglacial water pressures from ice boreholes in the Aletsch Glacier ablation area, as well as continuous monitoring of bedrock deformation from permanent Global Navigation Satellite Systems stations, help verify our model assumptions. While purely mechanical glacier loading cycles create only limited rock slope damage in our models, introducing a fluctuating groundwater table generates substantial new fracturing. Superposed annual groundwater cycles increase predicted damage. The cumulative effects are capable of destabilizing the eastern valley flank of our model in toppling‐mode failure, similar to field observations of active landslide geometry and kinematics. We find that hydromechanical fatigue is most effective acting in combination with long‐term loading and unloading of the slope during glacial cycles. Our results demonstrate that hydromechanical stresses associated with glacial cycles are capable of generating substantial rock slope damage and represent a key preparatory factor for paraglacial slope instabilities.

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Section: Comparison Of Preparatory Factors For Paraglacial Rock Slopementioning

confidence: 99%

Hydromechanical Rock Slope Damage During Late Pleistocene and Holocene Glacial Cycles in an Alpine Valley

et al. 2020

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“…The coupled model is called Dan3D-Flex, and has been used to simulate a large number of rock avalanche case histories (e.g. Aaron & Hungr 2016b;Castleton et al 2016;Grämiger et al 2016;Moore et al 2017). To couple the two models, the solution algorithm switches from the flexible block model to Dan3D at a user-specified time.…”

Section: Dan3d-flexmentioning

confidence: 99%

The role of initial coherence and path materials in the dynamics of three rock avalanche case histories

Aaron

McDougall

Moore

et al. 2017

Geoenviron Disasters

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Background: Rock avalanches are flow-like landslides that can travel at extremely rapid velocities and impact surprisingly large areas. The mechanisms that lead to the unexpected mobility of these flows are unknown and debated. Mechanisms proposed in the literature can be broadly classified into those that rely on intrinsic characteristics of the rock avalanche material, and those that rely on extrinsic factors such as path material. In this work a calibration-based numerical model is used to back-analyze three rock avalanche case histories. The results of these back-analyses are then used to infer factors that govern rock avalanche motion Results: Our study has revealed two key insights that must be considered when analyzing rock avalanches. Results from two of the case histories demonstrate the importance of accounting for the initially coherent phase of rock avalanche motion. Additionally, the back-analyzed basal resistance parameters, as well as the best-fit rheology, are different for each case history. This suggests that the governing mechanisms controlling rock avalanche motion are unlikely to be intrinsic. The back-analyzed strength parameters correspond well to those that would be expected by considering the path material that the rock avalanches overran. Conclusion: Our results show that accurate simulation of rock avalanche motion must account for the initially coherent phase of movement, and that the mechanisms governing rock avalanche motion are unlikely to be intrinsic to the failed material. Interaction of rock avalanche debris with path materials is the likely mechanism that governs the motion of many rock avalanches.

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“…These data suggest that the Belluno area is sensitive to seismic shakings originating even hundreds of km away. In the Alps, earthquakes have been suggested as triggers for several rock avalanches (e.g., Grämiger et al, 2016;Ivy-Ochs et al, 2017;Köpfli et al, 2018). The most important effect of the frequent seismic activity is the progressive increase in the rock fatigue, with the formation and subsequent weathering of failure planes (Friedmann et al, 2003;Brideau et al, 2009;Parker et al, 2013;Preisig et al, 2015;Gischig et al, 2016).…”

Section: Driving Factors and Possible Future Hazardsmentioning

confidence: 99%

Structural and climate drivers of the historic Masiere di Vedana rock avalanche (Belluno Dolomites, NE Italy)

Rossato

Ivy‐Ochs²,

Martin

et al. 2020

Preprint

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Abstract. The “Masiere di Vedana” rock avalanche, located in the Belluno Dolomites (NE Italy) at the foot of the Mt. Peron, is re-interpreted as Historic on the base of archaeological information and cosmogenic 36Cl exposure dates. The deposit is 9 km2 wide, has a volume of ~ 170 Mm3 correspondings to a pre-detachment rock mass of ~ 130 Mm3, and a maximum runout distance of 6 km and an H / L ratio of ~ 0.2. Differential velocities of the rock avalanche moving radially over different topography and path-material lead to the formation of specific landforms (tomas and compressional ridges). In the Mt. Peron crown the bedding is subvertical and includes carbonate lithologies from lower Jurassic (Calcari Grigi Group) to Cretaceous (Maiolica) in age. The proximal deposit is made of Calcari Grigi Group limestone, the distal deposit comprises upper Jurassic limestones (Fonzaso Formation, Rosso Ammonitico, and Maiolica), while the middle Jurassic Vajont Limestone dominates the central sector of the deposit. In the release area the bedding, the SSE-vergent frontal thrust planes, the NW-vergent backthrust planes, the NW-SE fracture planes, and the N-S Jurassic fault planes controlled the failure and enhanced the rock mass fragmentation. Cosmogenic 36Cl exposure ages, mean 1.90 ± 0.45 ka, indicate failure occurred between 340 BC and 560 AD. Although abundant Roman remains were found in sites surrounding the rock avalanche deposit, none was found within the deposit, and this is consistent with a Late Roman or early Middle Age failure. Seismic and climatic drivers are discussed. Over the last few hundred years, earthquakes up to Mw 6.3 including that at 365 AD, affected the Belluno area. Early in the first millennium, periods of climate worsening with increasing rainfall are known in the NE Alps. The combination of climate and earthquakes induced progressive long-term damage to the rock. The present Mt. Peron crown shows hundreds of meters-high rock prisms bound by backwall trenches, suggesting a potential landslide hazard for the whole mountain belt north of Belluno affected by the same structural characteristics.

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Two early Holocene rock avalanches in the Bernese Alps (Rinderhorn, Switzerland)

Cited by 39 publications

References 73 publications

Hydromechanical Rock Slope Damage During Late Pleistocene and Holocene Glacial Cycles in an Alpine Valley

Hydromechanical Rock Slope Damage During Late Pleistocene and Holocene Glacial Cycles in an Alpine Valley

The role of initial coherence and path materials in the dynamics of three rock avalanche case histories

Structural and climate drivers of the historic Masiere di Vedana rock avalanche (Belluno Dolomites, NE Italy)

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