Rock-Avalanche Activity in W and S Norway Peaks After the Retreat of the Scandinavian Ice Sheet

Hermanns, Reginald L.; Schleier, Markus; Böhme, Martina; Blikra, Lars Harald; Gosse, John C.; Ivy‐Ochs, Susan; Hilger, Paula

doi:10.1007/978-3-319-53483-1_39

Cited by 27 publications

(27 citation statements)

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“…-The 'deglaciation-close-tracking model' is characterized by a dominant peak in RSF activity immediately (i.e. Hermanns et al (2017) found nearly half of 22 dated rock avalanches in southwest Norway occurred within the first millennium following local deglaciation. The temporal pattern of activity is therefore a typical paraglacial response (Ballantyne 2002).…”

Section: Previous Models Of the Timing Of Rsfsmentioning

confidence: 99%

“…Causal factors that may account for such a pattern include glacial unloading, glacial debuttressing, stress-release fracturing, enhanced groundwater pressure in rock joints and permafrost degradation, all closely associated in time with deglaciation (Fischer et al 2006;Cossart et al 2008;McColl 2012;McColl & Davies 2012;Ballantyne et al 2014a, b;B€ ohme et al 2015;Deline et al 2015;Mercier et al 2017). Hermanns et al (2017) found nearly half of 22 dated rock avalanches in southwest Norway occurred within the first millennium following local deglaciation. Although the majority of RSF events occur shortly after deglaciation, some occur much later, due to timedependent fracture propagation and progressive failure (Eberhardt et al 2004;Krautblatter et al 2013;Phillips et al 2017).…”

Section: Previous Models Of the Timing Of Rsfsmentioning

confidence: 99%

“…The primary method for numerical age dating of RSF deposits is terrestrial cosmogenic nuclide dating (TCND; associated with RSFs (Hermanns et al 2001(Hermanns et al , 2004(Hermanns et al , 2017Cossart et al 2008;Dortch et al 2009;Ivy-Ochs et al 2009;Penna et al 2011;Ballantyne & Stone 2013;Ballantyne et al , 2014aB€ ohme et al 2015;Schleier et al 2015Schleier et al , 2017. However, the high financial cost of this technique limits its routine application, which, in turn, often prevents statistically robust identification and rejection of erroneous results (Tomkins et al 2018b).…”

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confidence: 99%

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Small rock‐slope failures conditioned by Holocene permafrost degradation: a new approach and conceptual model based on Schmidt‐hammer exposure‐age dating, Jotunheimen, southern Norway

Matthews

Winkler

Wilson

et al. 2018

Boreas

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October): Small rock-slope failures conditioned by Holocene permafrost degradation: a new approach and conceptual model based on Schmidt-hammer exposure-age dating, Jotunheimen, southern Norway.Rock-slope failures (RSFs) constitute significant natural hazards, but the geophysical processes that control their timing are poorly understood. However, robust chronologies can provide valuable information on the environmental controls on RSFoccurrence: information that can inform models of RSF activity in response to climatic forcing. This study uses Schmidt-hammer exposure-age dating (SHD) of boulder deposits to construct a detailed regional Holocene chronology of the frequency and magnitude of small rock-slope failures (SRSFs) in Jotunheimen, Norway. By focusing on the depositional fans of SRSFs (≤10 3 m 3 ), rather than on the corresponding features of massive RSFs (~10 8 m 3 ), 92 singleevent RSFs are targeted for chronology building. A weighted SHD age-frequency distribution and probability density function analysis indicated four centennial-to millennial-scale periods of enhanced SRSF frequency, with a dominant mode at~4.5 ka. Using change detection and discreet Meyer wavelet analysis, in combination with existing permafrost depth models, we propose that enhanced SRSFactivity was primarily controlled by permafrost degradation. Long-term relative change in permafrost depth provides a compelling explanation for the high-magnitude departures from the SRSF background rate and accounts for: (i) the timing of peak SRSF frequency; (ii) the significant lag (~2.2 ka) between the Holocene Thermal Maximum and the SRSF frequency peak; and (iii) the marked decline in frequency in the late-Holocene. This interpretationis supported bygeomorphological evidence, as the spatialdistributionofSRSFs isstrongly correlatedwith the aspect-dependent lower altitudinal limit ofmountain permafrost in clifffaces. Resultsare indicative of a causal relationship between episodes of relatively warm climate, permafrost degradation and the transition to a seasonal-freezing climatic regime. This study highlights permafrost degradation as a conditioning factor for cliff collapse, and hence the importance of paraperiglacial processes; a result with implications for slope instability in glacial and periglacial environments under global warming scenarios.

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Section: Previous Models Of the Timing Of Rsfsmentioning

confidence: 99%

Section: Previous Models Of the Timing Of Rsfsmentioning

confidence: 99%

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confidence: 99%

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Small rock‐slope failures conditioned by Holocene permafrost degradation: a new approach and conceptual model based on Schmidt‐hammer exposure‐age dating, Jotunheimen, southern Norway

Matthews

Winkler

Wilson

et al. 2018

Boreas

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“…Recent studies reveal a rapid rock slope instability response to the initial local decay of the Scandinavian ice sheet followed by a lower and constant frequency following the climate optimum in the Holocene (e.g. Hermanns et al, 2017;. In northern Norway, two periods of major seismicity (earthquakes on the order of ≥ 6.0 M w ) have been suggested, due to the stresses following the postglacial uplift: one before 11 000 14 C years BP and one between 10 000 and 9500 years BP.…”

Section: Glaciation and Deglaciation History Postglacial Upliftmentioning

confidence: 99%

Ground thermal and geomechanical conditions in a permafrost-affected high-latitude rock avalanche site (Polvartinden, northern Norway)

et al. 2018

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Abstract. On 26 June 2008, a rock avalanche detached in the northeast facing slope of Polvartinden, a high-alpine mountain in Signaldalen, northern Norway. Here, we report on the observed and modelled past and present near-surface temperature regime close to the failure zone, as well as on a subsequent simulation of the subsurface temperature regime, and on initial geomechanical mapping based on laser scanning. The volume of the rock avalanche was estimated to be approximately 500 000 m3. The depth to the actual failure surface was found to range from 40 m at the back of the failure zone to 0 m at its toe. Visible in situ ice was observed in the failure zone just after the rock avalanche. Between September 2009 and August 2013, ground surface temperatures were measured with miniature temperature data loggers at 14 different localities, close to the original failure zone along the northern ridge of Polvartinden and on the valley floor. The results from these measurements and from a basic three-dimensional heat conduction model suggest that the lower altitudinal limit of permafrost at present is at 600–650 m a.s.l., which corresponds to the upper limit of the failure zone. A coupling of our in situ data with regional climate data since 1958 suggests a general gradual warming and that the period with highest mean near surface temperatures on record ended four months before the Signaldalen rock avalanche detached. A comparison with a transient permafrost model run at 10 m depth, representative for areas where snow accumulates, strengthen these findings, which are also in congruence with measurements in nearby permafrost boreholes. It is likely that permafrost in and near the failure zone is presently subject to degradation. This degradation, in combination with the extreme warm year antecedent to the rock failure, is seen to have played an important role in the detaching of the Signaldalen rock avalanche.

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“…If the latter (i.e., paraglacial processes were operating and had contributed to slope priming) it provides a relatively rare example of an early (in the deglaciation history) rockslope response to glacier retreat (c.f. McColl, 2012;Hermanns et al, 2017), similar to only a small number of (>15 ka) RSFs in the Scottish Highlands where the timing of post-glacial RSFs is well-recorded (Ballantyne et al, 2014) and few other examples globally (Pánek, 2019).…”

Section: The Causes Of the Bush Stream Rock Avalanchementioning

confidence: 68%

The Anomalously Old Bush Stream Rock Avalanche and Its Implications for Landslide Inventories in Dynamic Landscapes

McColl

2020

Front. Earth Sci.

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Previous dating of rock slope failures in most glaciated mountain chains has revealed almost exclusively young, mostly Holocene ages. In this study, a rock avalanche in the glaciated Rangitata Basin in Canterbury, New Zealand is mapped, described, and dated, revealing a pre-Holocene age of failure. The geomorphology and characteristics of the rock avalanche, named here as the Bush Stream Rock Avalanche, were assessed from field mapping and photogrammetric analyses. To assess the age of the rock avalanche, in situ cosmogenic 10 Be exposure dating was applied to boulders on the deposit. The geomorphological mapping shows that the morphology of the head scarp and deposit of the rock avalanche are distinct from the surrounding landscape, much of which appears to be glacial in origin. The rock avalanche traveled about 4 km, with a volume of 50-100 M m 3 , and appears to have temporarily blocked Bush Stream. The dated boulders suggest an age of >16 ka (and likely >20 ka), making it the oldest reported alpine rock avalanche in New Zealand, and one of the oldest last-glaciation rock avalanches to be reported worldwide. Deep depressions, possibly kettle holes, in the deposit are indicative of runout over a glacier (or associated dead ice), but any glacier present at the time must have been small and probably decaying. The excellent preservation was likely favored by a small catchment located on the dry lee side of the Two Thumb Range which dampened glacial and fluvial activity. The study confirms that rock avalanches were being produced in the Southern Alps early in the last glaciation or early period of deglaciation, but that evidence for them likely exists only in the rare environments that have conditions favorable for preservation. Preservation potential in most of the Southern Alps is low, with older deposits readily buried or eroded by New Zealand's high rates of erosion, aggradation, and dynamic processes. Unless methods can be developed to identify missing older events, we are hampered in our ability to understand the frequency, and therefore causes, of large slope failures in the Southern Alps and in other highly dynamic alpine landscapes.

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Rock-Avalanche Activity in W and S Norway Peaks After the Retreat of the Scandinavian Ice Sheet

Cited by 27 publications

References 14 publications

Small rock‐slope failures conditioned by Holocene permafrost degradation: a new approach and conceptual model based on Schmidt‐hammer exposure‐age dating, Jotunheimen, southern Norway

Small rock‐slope failures conditioned by Holocene permafrost degradation: a new approach and conceptual model based on Schmidt‐hammer exposure‐age dating, Jotunheimen, southern Norway

Ground thermal and geomechanical conditions in a permafrost-affected high-latitude rock avalanche site (Polvartinden, northern Norway)

The Anomalously Old Bush Stream Rock Avalanche and Its Implications for Landslide Inventories in Dynamic Landscapes

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