Within the Innfjorddalen valley (Møre og Romsdal, Norway) a 1.5 km long linear NNE-SSW striking f... more Within the Innfjorddalen valley (Møre og Romsdal, Norway) a 1.5 km long linear NNE-SSW striking feature, forming a 3-4 m high step in the topography, occurs on the SE facing slope of the Middagstinden mountain and was previously discussed as a Holocene reverse fault, called the "Berill fault". Our intense structural field mapping and a high resolution digital elevation model based on LiDAR data derived from airborne and terrestrial laser scanning indicate that the "Berill fault" is a normal fault that has the orientation of the collapse of the Caledonian orogen, that is today reactivated as a limiting structure of a Deep Seated Gravitational Slope Deformation (DSGSD). Differential Global Navigation Satellite System (dGNSS) surveys over the instability indicate velocities of the DSGSD of ca. 0.6 cm/yr. Three electric resistivity profiles on the valley floor attest that the fault is a structure with regional extend. Three trenches with a total length of 100 m paral...
A monitoring programme was started in the autumn 2001 on Dovrefjell, southern Norway, to measure ... more A monitoring programme was started in the autumn 2001 on Dovrefjell, southern Norway, to measure ground temperatures in 11 boreholes approximately 9 m deep along an altitudinal transect across the mountain permafrost transition zone. This is the first transect of this type set up in Scandinavia. Borehole temperatures are highly correlated with elevation. Measurements of mean ground temperatures at 8.5 m depth on exposed sites show that the lower limit of the mountain permafrost is on the high side of 1300 m a.s.l. The mean ground temperature elevation gradient was found to be �0.7°C/100 m. This gradient was not dependent on snow depth, and differs from the mean annual air temperature lapse rate (�0.44°C/100 m). The gradient differences may be due to stronger turbulent fluxes at high elevations during the snow-free period.
Rock glaciers are complex systems of mountain permafrost creep. Their evolution involves among ot... more Rock glaciers are complex systems of mountain permafrost creep. Their evolution involves among others headwall weathering and debris deposition, incorporation of ice and snow in the permafrost body, ground thermal conditions, mass transport by deformation and loss of ice and solids by melt or erosion. These factors are significantly influenced by the atmospheric conditions. In this contribution, we numerically estimate
Gamanjunni 3 is an unstable rock slope in Manndal Valley, northern Norway, that shows active defo... more Gamanjunni 3 is an unstable rock slope in Manndal Valley, northern Norway, that shows active deformation. It extends from the top of the slope at ~1200 m asl down to ~600 m asl and its maximum volume is estimated with 15 million m³. Until present a vertical downward displacement of ~100 m is observable. The unstable rock slope displays a high degree of internal fracturing and a high rockfall activity at its front and the southern lateral limit. Field observations indicate that this unstable rock slope consists of different compartments. Structural mapping and analyses of terrestrial laser scans identified many discontinuities. However, none of those may act as a basal failure surface based on kinematical analysis. Also geophysical investigations (ground-based resistivity) do not indicate any clear structure that may form a basal limit. Different displacement measurement systems (differential GNSS, terrestrial laser scanning, ground- and satellite-based InSAR) show yearly average dis...
Development of earth observation techniques such as differential Global Navigation Satellite Syst... more Development of earth observation techniques such as differential Global Navigation Satellite Systems (dGNSS), terrestrial laser scanning (TLS) or radar interferometry (InSAR) made it possible in the past decades to measure yearly displacement rates in the range of centimetres and sub centimetres. Gravitationally driven slope deformation are measured in Norway and around the world on critical slopes with those techniques. However as the measurement period is so far short (up to a maximum of ca. a decade or two) the displacement rates determined are difficult to interpret as the long-term displacement rates since displacement initiation are unknown. We apply terrestrial cosmogenic nuclide (TCN) dating on sliding surfaces exposed by rockslides in order to determine long-term displacement rates to compare them to present day velocities. We sampled sliding surfaces of currently active rockslides that have either failed at least once in prehistoric times or not yet undergone catastrophic ...
Rock slope failures form a frequent hazard to many populated mountain regions. Especially in west... more Rock slope failures form a frequent hazard to many populated mountain regions. Especially in western Norway, the topographical and meteorological characteristics increase the vulnerability for rock slope failures. A major focus for studies in Norway is to eciently nd and investigate possible future rock slope failures in order to prevent extensive humanitarian disasters. The determination of the critical parameters involved in the development of rock slope failures is crucial in order to optimize hazard recognition. In addition, a better understanding of the spatial and temporal variability of prehistoric and historic rock slope failures as well as present day rock slope instabilities will optimize monitoring and further research on the susceptibility for future rock slope failures.The primary aim of this study is to investigate the spatial and temporal distribution of rock slope instabilities within western Norway. It is further aimed to determine the controlling parameters on the development of rock slope instabilities within the study region. The implemented approaches range from regional scale statistical analyses towards site specic numerical modelling, while a focus is set on quantitative analyses.Within this thesis the main controlling parameters are dened for rockfalls and rock slope instabilities on a regional scale for the entire county of Sogn & Fjordane, western Norway. It is demonstrated that always a combination of several parameters is necessary to destabilize a mountain side. Rockfalls have the strongest spatial relation to the presence of bare rock as well as landslide deposits, the degree of tectonic deformation and the geological lineament density. Large rock slope instabilities develop preferentially within relatively weak rock units, such as phyllites or weathered mac gneisses, and at convex slope breaks. Looking more into detail, a strong structural control is conrmed by numerical modelling for the unstable rock slope at Stampa.Susceptibility and hazard are assessed at dierent scales and with dierent measures. Quantitative rockfall susceptibility is mapped on a regional scale for the entire county of Sogn & Fjordane based on the statistical analysis of a set of controlling factors. In addition, this statistical susceptibility model is combined with a physically based model, restricting the susceptibility map to areas that are steep enough to represent a potential rockfall source. This combination allows using road inventories, with registered impact points instead of release areas, for susceptibility modelling. In contrast, relative susceptibility and also hazard are assessed locally for single parts of the unstable rock slope at Stampa based on morphology and past activity. Present day annual expectable frequencies for rock slope failures of certain volume classes are determined for the Storfjord region in western Norway based on magnitude-frequency analyses. Furthermore, a semi quantitative hazard estimation is obtained for each potential instability based on a qualitative susceptibility assessment of each instability in this region.This PhD thesis presents results of the rst attempts of quantitative statistical analyses of dierent inventories covering rock slope instabilities in Norway. It is shown that susceptibility and hazard can be assessed with dierent measures, forming the basis for further decisions regarding risk assessment and mitigation.
Airborne scanning laser altimetry is a relatively new technique for remote sensing of ground elev... more Airborne scanning laser altimetry is a relatively new technique for remote sensing of ground elevation. A laser ranger is scanned across a swath beneath the aircraft, producing a two-dimensional distribution of elevations when combined with data on aircraft position and orientation. Smooth snow-covered glaciers are ideal surfaces for laser scanning since they are highly reflective. A new prototype laser system is described together with results from Hardangerjökulen, Norway. An analysis of the data shows that noise levels are very low at around 2 cm, and that repeatability between overlapping swaths is approximately ± 10 cm. This is consistent with an absolute accuracy of 15 cm or better from manufacturer’s and other measurements. Swath widths of over 1 km are attainable, at lowing complete coverage of small to medium-sized glaciers using parallel flight tracks. The high accuracy and dense, even coverage (about 20 000 points per km2) gives good-quality derived products such as DEMs ...
During the last decades most glaciers in the world have retreated. However, some of the glaciers ... more During the last decades most glaciers in the world have retreated. However, some of the glaciers in the western part of Norway have advance during the last 10 years. This is related to increased winter precipitation in the late 1980's and the beginning of the 1990's. As a results the glacier fronts have grown steeper, more active and thereby more dangerous. The ice cap Jostedalsbreen (468 km2) is one of the most visited glaciated areas in Norway where hundreds of tourists come every day during the summer season. It is popular for glacier climbing, both as guided tours and in individual groups. The steep advancing glacier fronts have made this activity more difficult over the last years. Several ice blocks have also broken off at the front. Although large icefalls from hanging glaciers happen very rarely, the consequences of such events can be dramatic. In order to survey this relative large glacier several aerial photographs was taken in August 2001. The same strips were flo...
The aim of GLACIODYN is to reduce the uncertainties in Arctic Glaciers and Ice Cap (GIC) contribu... more The aim of GLACIODYN is to reduce the uncertainties in Arctic Glaciers and Ice Cap (GIC) contribution to sea level changes. This involves to include calving in mass budget calculations, improve process understanding of calving and basal sliding and include dynamics in modeling of future glacier response. Selected target GICs have been studied in the Arctic. In this presentation we
Hessbreen is a 5km2, polythermal glacier in southern Spitsbergen. It is believed to have surged a... more Hessbreen is a 5km2, polythermal glacier in southern Spitsbergen. It is believed to have surged at the end of the 19th century, and another surge started in 1969, not in 1972 as earlier studies suggested. The surge was probably triggered in the middle section of the glacier and affected the upper part approximately 4 years before including the whole glacier. Present velocities are low, increasing from 0.3m a-1 at the snout to 4.8 m a-1 above the equilibrium line. A distinct velocity reduction occurs where the glacier narrows. This suggests the velocities here are affected by the cold marginal and frontal ice. Large seasonal variations, with summer velocities of more than twice the winter velocities in the middle part of the glacier, indicate a seasonal change in the drainage system in this area. In the lower part there is no apparent sliding. The balance-flux estimate indicates that the actual ice flux is only about 50% of that required for steady state, so Hessbreen appears to be b...
Within the Innfjorddalen valley (Møre og Romsdal, Norway) a 1.5 km long linear NNE-SSW striking f... more Within the Innfjorddalen valley (Møre og Romsdal, Norway) a 1.5 km long linear NNE-SSW striking feature, forming a 3-4 m high step in the topography, occurs on the SE facing slope of the Middagstinden mountain and was previously discussed as a Holocene reverse fault, called the "Berill fault". Our intense structural field mapping and a high resolution digital elevation model based on LiDAR data derived from airborne and terrestrial laser scanning indicate that the "Berill fault" is a normal fault that has the orientation of the collapse of the Caledonian orogen, that is today reactivated as a limiting structure of a Deep Seated Gravitational Slope Deformation (DSGSD). Differential Global Navigation Satellite System (dGNSS) surveys over the instability indicate velocities of the DSGSD of ca. 0.6 cm/yr. Three electric resistivity profiles on the valley floor attest that the fault is a structure with regional extend. Three trenches with a total length of 100 m paral...
A monitoring programme was started in the autumn 2001 on Dovrefjell, southern Norway, to measure ... more A monitoring programme was started in the autumn 2001 on Dovrefjell, southern Norway, to measure ground temperatures in 11 boreholes approximately 9 m deep along an altitudinal transect across the mountain permafrost transition zone. This is the first transect of this type set up in Scandinavia. Borehole temperatures are highly correlated with elevation. Measurements of mean ground temperatures at 8.5 m depth on exposed sites show that the lower limit of the mountain permafrost is on the high side of 1300 m a.s.l. The mean ground temperature elevation gradient was found to be �0.7°C/100 m. This gradient was not dependent on snow depth, and differs from the mean annual air temperature lapse rate (�0.44°C/100 m). The gradient differences may be due to stronger turbulent fluxes at high elevations during the snow-free period.
Rock glaciers are complex systems of mountain permafrost creep. Their evolution involves among ot... more Rock glaciers are complex systems of mountain permafrost creep. Their evolution involves among others headwall weathering and debris deposition, incorporation of ice and snow in the permafrost body, ground thermal conditions, mass transport by deformation and loss of ice and solids by melt or erosion. These factors are significantly influenced by the atmospheric conditions. In this contribution, we numerically estimate
Gamanjunni 3 is an unstable rock slope in Manndal Valley, northern Norway, that shows active defo... more Gamanjunni 3 is an unstable rock slope in Manndal Valley, northern Norway, that shows active deformation. It extends from the top of the slope at ~1200 m asl down to ~600 m asl and its maximum volume is estimated with 15 million m³. Until present a vertical downward displacement of ~100 m is observable. The unstable rock slope displays a high degree of internal fracturing and a high rockfall activity at its front and the southern lateral limit. Field observations indicate that this unstable rock slope consists of different compartments. Structural mapping and analyses of terrestrial laser scans identified many discontinuities. However, none of those may act as a basal failure surface based on kinematical analysis. Also geophysical investigations (ground-based resistivity) do not indicate any clear structure that may form a basal limit. Different displacement measurement systems (differential GNSS, terrestrial laser scanning, ground- and satellite-based InSAR) show yearly average dis...
Development of earth observation techniques such as differential Global Navigation Satellite Syst... more Development of earth observation techniques such as differential Global Navigation Satellite Systems (dGNSS), terrestrial laser scanning (TLS) or radar interferometry (InSAR) made it possible in the past decades to measure yearly displacement rates in the range of centimetres and sub centimetres. Gravitationally driven slope deformation are measured in Norway and around the world on critical slopes with those techniques. However as the measurement period is so far short (up to a maximum of ca. a decade or two) the displacement rates determined are difficult to interpret as the long-term displacement rates since displacement initiation are unknown. We apply terrestrial cosmogenic nuclide (TCN) dating on sliding surfaces exposed by rockslides in order to determine long-term displacement rates to compare them to present day velocities. We sampled sliding surfaces of currently active rockslides that have either failed at least once in prehistoric times or not yet undergone catastrophic ...
Rock slope failures form a frequent hazard to many populated mountain regions. Especially in west... more Rock slope failures form a frequent hazard to many populated mountain regions. Especially in western Norway, the topographical and meteorological characteristics increase the vulnerability for rock slope failures. A major focus for studies in Norway is to eciently nd and investigate possible future rock slope failures in order to prevent extensive humanitarian disasters. The determination of the critical parameters involved in the development of rock slope failures is crucial in order to optimize hazard recognition. In addition, a better understanding of the spatial and temporal variability of prehistoric and historic rock slope failures as well as present day rock slope instabilities will optimize monitoring and further research on the susceptibility for future rock slope failures.The primary aim of this study is to investigate the spatial and temporal distribution of rock slope instabilities within western Norway. It is further aimed to determine the controlling parameters on the development of rock slope instabilities within the study region. The implemented approaches range from regional scale statistical analyses towards site specic numerical modelling, while a focus is set on quantitative analyses.Within this thesis the main controlling parameters are dened for rockfalls and rock slope instabilities on a regional scale for the entire county of Sogn & Fjordane, western Norway. It is demonstrated that always a combination of several parameters is necessary to destabilize a mountain side. Rockfalls have the strongest spatial relation to the presence of bare rock as well as landslide deposits, the degree of tectonic deformation and the geological lineament density. Large rock slope instabilities develop preferentially within relatively weak rock units, such as phyllites or weathered mac gneisses, and at convex slope breaks. Looking more into detail, a strong structural control is conrmed by numerical modelling for the unstable rock slope at Stampa.Susceptibility and hazard are assessed at dierent scales and with dierent measures. Quantitative rockfall susceptibility is mapped on a regional scale for the entire county of Sogn & Fjordane based on the statistical analysis of a set of controlling factors. In addition, this statistical susceptibility model is combined with a physically based model, restricting the susceptibility map to areas that are steep enough to represent a potential rockfall source. This combination allows using road inventories, with registered impact points instead of release areas, for susceptibility modelling. In contrast, relative susceptibility and also hazard are assessed locally for single parts of the unstable rock slope at Stampa based on morphology and past activity. Present day annual expectable frequencies for rock slope failures of certain volume classes are determined for the Storfjord region in western Norway based on magnitude-frequency analyses. Furthermore, a semi quantitative hazard estimation is obtained for each potential instability based on a qualitative susceptibility assessment of each instability in this region.This PhD thesis presents results of the rst attempts of quantitative statistical analyses of dierent inventories covering rock slope instabilities in Norway. It is shown that susceptibility and hazard can be assessed with dierent measures, forming the basis for further decisions regarding risk assessment and mitigation.
Airborne scanning laser altimetry is a relatively new technique for remote sensing of ground elev... more Airborne scanning laser altimetry is a relatively new technique for remote sensing of ground elevation. A laser ranger is scanned across a swath beneath the aircraft, producing a two-dimensional distribution of elevations when combined with data on aircraft position and orientation. Smooth snow-covered glaciers are ideal surfaces for laser scanning since they are highly reflective. A new prototype laser system is described together with results from Hardangerjökulen, Norway. An analysis of the data shows that noise levels are very low at around 2 cm, and that repeatability between overlapping swaths is approximately ± 10 cm. This is consistent with an absolute accuracy of 15 cm or better from manufacturer’s and other measurements. Swath widths of over 1 km are attainable, at lowing complete coverage of small to medium-sized glaciers using parallel flight tracks. The high accuracy and dense, even coverage (about 20 000 points per km2) gives good-quality derived products such as DEMs ...
During the last decades most glaciers in the world have retreated. However, some of the glaciers ... more During the last decades most glaciers in the world have retreated. However, some of the glaciers in the western part of Norway have advance during the last 10 years. This is related to increased winter precipitation in the late 1980's and the beginning of the 1990's. As a results the glacier fronts have grown steeper, more active and thereby more dangerous. The ice cap Jostedalsbreen (468 km2) is one of the most visited glaciated areas in Norway where hundreds of tourists come every day during the summer season. It is popular for glacier climbing, both as guided tours and in individual groups. The steep advancing glacier fronts have made this activity more difficult over the last years. Several ice blocks have also broken off at the front. Although large icefalls from hanging glaciers happen very rarely, the consequences of such events can be dramatic. In order to survey this relative large glacier several aerial photographs was taken in August 2001. The same strips were flo...
The aim of GLACIODYN is to reduce the uncertainties in Arctic Glaciers and Ice Cap (GIC) contribu... more The aim of GLACIODYN is to reduce the uncertainties in Arctic Glaciers and Ice Cap (GIC) contribution to sea level changes. This involves to include calving in mass budget calculations, improve process understanding of calving and basal sliding and include dynamics in modeling of future glacier response. Selected target GICs have been studied in the Arctic. In this presentation we
Hessbreen is a 5km2, polythermal glacier in southern Spitsbergen. It is believed to have surged a... more Hessbreen is a 5km2, polythermal glacier in southern Spitsbergen. It is believed to have surged at the end of the 19th century, and another surge started in 1969, not in 1972 as earlier studies suggested. The surge was probably triggered in the middle section of the glacier and affected the upper part approximately 4 years before including the whole glacier. Present velocities are low, increasing from 0.3m a-1 at the snout to 4.8 m a-1 above the equilibrium line. A distinct velocity reduction occurs where the glacier narrows. This suggests the velocities here are affected by the cold marginal and frontal ice. Large seasonal variations, with summer velocities of more than twice the winter velocities in the middle part of the glacier, indicate a seasonal change in the drainage system in this area. In the lower part there is no apparent sliding. The balance-flux estimate indicates that the actual ice flux is only about 50% of that required for steady state, so Hessbreen appears to be b...
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