Why permafrost rocks become unstable : a rock–ice-mechanical model in time and space
Climatic warming ; Glacial features ; Ice ; Ice wedges ; Mass movement ; Model ; Mountain ; Paraglacial ; Permafrost ; Rock mechanics ; Slope dynamics ; Space time
Here, the AA. develop a mechanical model that relates the destabilization of thawing permafrost rock slopes to temperature-related effects on both, rock- and ice-mechanics; and laboratory testing of key assumptions is performed. The destabilization
-saturated rock thaws. Based on literature and experiments, the AA. develop a modified Mohr-Coulomb failure criterion for ice-filled rock fractures that incorporates fracturing of rock bridges, friction of rough fracture surfaces, ductile creep of ice
and detachment mechanisms along rock-ice interfaces. Novel laboratory setups were developed to assess the temperature dependency of the friction of ice-free rock-rock interfaces and the shear detachment of rock-ice interfaces. The model explains why all
magnitudes of rock–slope failures can be prepared and triggered by permafrost degradation and is capable of conditioning long para-glacial response times.
Linking weathering and rock slope instability : non-linear perspectives
Weathering is linked complexly to the erosion and evolution of rock slopes. Weathering influences both the strength of rock slopes and the stresses that act upon them. While weathering has often been portrayed in an over-simplified way by those
studying rock slope instability, in reality it consists of multiple processes, acting over different spatial and temporal scales, with many complex inter-linkages. Through a demonstration of the sources of non-linearities in rock slope weathering systems
and their implications for rock slope instability, this paper proposes five key linkages worthy of further study.
Evidencing a large body of ice in a rock glacier, Vanoise Massif, Northern French Alps
Alpes du Nord ; France ; Glacier ; Ground penetrating radar ; Periglacial features ; Permafrost ; Photogrammetry ; Rock glacier ; Surface temperature ; Thermal regime ; Vanoise
The Sachette rock glacier is an active rock glacier located between 2 660 and 2 480 m a.s.l. in the Vanoise Massif. In order to characterize its status as permafrost feature, shallow ground temperatures were monitored and the surface velocity
measured by photogrammetry. The rock glacier exhibits near-surface thermal regimes suggesting permafrost occurrence and also displays significant surface horizontal displacements. In order to investigate its internal structure, a ground-penetrating radar
(GPR) survey was performed. The results point towards the existence of a large buried body of ice in the upper part of the rock glacier. The rock glacier was interpreted to result from the former advance and decay of a glacier onto pre-existing deposits
, and from subsequent creep of the whole assemblage. This study of the Sachette rock glacier thus highlights the rock glacier as a transitional landform involving the incorporation and preservation of glacier ice in permafrost environments with subsequent
Relict talus-foot rock glaciers at Øyberget, Upper Ottadalen, Southern Norway : Schmidt hammer exposure ages and palaeoenvironmental implications
Dating ; Deglaciation ; Holocene ; Inheritated geomorphological features ; Norway ; Palaeo-environment ; Periglacial features ; Permafrost ; Rock glacier ; Southern Norway
Three relict talus-foot rock glaciers at Øyberget, upper Ottadalen, were dated using high-precision Schmidt hammer exposure-age dating (SHD). A SHD calibration curve was constructed for the local banded gneiss using 2 control points : 1) fresh
bedrock in a road cutting; and 2) glacially scoured bedrock surfaces deglaciated c. 9.7 ka. obtained for the 3 rock glaciers located ~ 1000 m below the present lower limit of mountain permafrost, at a site covered by glacier ice throughout the Late
Weichselian. Two interpretations are presented. First, the rock glaciers may be paraglacial features, the SHD ages are therefore a true reflection of rock glacier age. Second, the rock glaciers may have formed during several thousand years of permafrost
conditions in the Mid-Weichselian (possibly during the Ålesund Interstadial), then the true age of the rock glaciers is much older than their SHD ages. Although evidence is currently insufficient to distinguish between these 2 interpretations, the paper
demonstrates both the potential and limitations of high-precision SHD in the context of rock glaciers.
The western part of the Uppony Mountains consists of mainly Palaeozoic (Ordovician-Permian) rock. At the lower parts of the Mountains, where the Csernely Creek springs, the rock is of unconsolidated sea deposits from the Lower Miocene age
. In present days the Csernely Creek cuts into the higher relief Palaeozoic rock and crosses it through a narrow gorge. There is one explanation for this. The Palaeozoic rocks must have been covered with the Lower Miocene rocks. On the top
of these unconsolidated sea deposits started the development of the valley of the Csernely Creek at the end of the Lower Miocene and in the Middle Miocene age. In the meanwhile the Palaeozoic rocks under these Miocene deposits had been lifted by tectonic movements and all
Internal structure and permafrost characteristics of the rock glaciers of Southern Carpathians (Romania) assessed by geoelectrical soundings and thermal monitoring
Carpathian Mountains ; Electrical resistivity ; Geophysics ; Mountain ; Periglacial features ; Permafrost ; Rock glacier ; Romania ; Surface temperature
Six rock glaciers in the Southern Carpathians have been investigated by means of geoelectrical soundings in order to detect their internal stratigraphy and the existence of frozen sediments. In the case of 3 relict rock glaciers, the electrical
resistivity measurements indicated a typical internal structure. Low resistivity values which are typical of unfrozen fine-grained materials were obtained, but high resistivity values measured in the Pietroasa, Ieşu and Pietrele rock glaciers denote
the presence of sediments cemented by interstitial ice and ice lenses. Based on the moderate resistivity values, the ice content is probably low to medium in the upper portion of these rock glaciers. At 2 sites (Pietroasa and Văiuga rock glaciers), ground
Rock damage and regolith transport by frost : an example of climate modulation of the geomorphology of the critical zone
comprise rock detachment into the mobile layer, mobile regolith transport, and a channel incision or aggradation boundary condition. They extend this system into the deep critical zone by considering a weathering damage zone below the mobile regolith
in which rock strength is diminished. The AA. first discuss generic damage profiles in which appropriate length and damage scales govern profile shapes, and examine their dependence upon exhumation rate. They then introduce climate control through
the example of rock damage by frost-generated crack growth. Finally the AA. link the frost cracking damage model, a mobile regolith production rule in which rock entrainment is conditioned by the damage state of the rock, and a frost creep transport model
of hard calcrete rock outcrops (Nari) on chalk. A field study was conducted to measure visual surface coverage of 5 components : S.p., shrub (excluding S.p. and including other dwarf shrubs and trees), annuals, rock, and bare soil. The results show
that rock, an abiotic component, plays an important role in this semi-arid landscape. Among the studied components, the relationship between rock and S.p. was found to be the strongest. As rock presence decreases, S.p. distribution increases. The threshold
for S.p. dominance is rock coverage below 14%. The results show that the rock/S.p. ratio controls changes in the landscape structure varying from stable heterogenic mosaic to stable homogeneous S.p. matrix.
Application of Schmidt hammer relative age dating to Late Pleistocene moraines and rock glaciers in the Western Tatra Mountains, Slovakia
Dating ; Deglaciation ; Glacial features ; Moraine ; Mountain ; Palaeogeography ; Periglacial features ; Research technique ; Rock glacier ; Slovak Republic ; Tatra Mountains ; Upper Pleistocene
In order to evaluate the potential of the Schmidt hammer for relative age dating of Late Pleistocene moraines and rock glaciers, rebound (R) values were collected at 38 sites in 2 formerly glaciated valleys in the Western Tatras in northern Slovakia
. A large statistical population of measurements obtained from moraine and rock glacier surfaces was used to analyze the variability of mean R-values in the same lithology and overall southern valley exposition. Four separate sets of glacial/periglacial
relationships were taken together to reconstruct the pattern of deglaciation on southern Tatra slopes. The high dating potential of the Schmidt hammer for older rock surfaces is shown. With this method, it is possible to differentiate between Late Glacial
moraines and rock glacier systems of different age.
Kent’s Sweden, or what a rock band can tell us about a nation
Culturel ; Eskilstuna ; Groupe de rock ; Identité nationale ; Musique ; Paysage urbain ; Stockholm ; Suède
L’A. analyse de quelle manière le groupe de rock suédois, Kent, représente t’il la quintessence du pays de par leurs débuts dans leur ville d’origine, Eskilstuna, puis de par leur décision de s’installer à Stockholm, symbole de leur mobilité sociale
by non-carbonate crystalline metamorphic rock. Marble corrosion is caused primarily by the influx of allogenic waters from the non-carbonate part of the catchment. Hydrochemical measurements were made over the course of 8 years. The calculated denudation
Rock samples from Marion Island in the Sub-Antarctic and from the Drakensberg, South Africa were divided into sets and subjected to wetting and drying at 2 different moisture amplitudes to determine changes in physical rock properties. Rock porosity
of wetting and drying cycles is a more important factor than the degree to which the samples have been saturated; 2) changes in rock properties were detected for the control samples as well as the field samples, suggesting that the experimental techniques
used for determining the rock properties have themselves affected the samples; 3) samples that outwardly appeared very similar have responded differently to wetting and drying. This implies that even small changes in internal rock structure can have
Cold area ; Geophysics ; Instrumentation ; Rock mechanics ; Temperature ; Thermal stress ; Threshold ; Weathering
Rock surface temperature changes in excess of 2°C min-1 have been argued to result in permanent strain in rock. The single threshold value and the supposed importance of a rate of 2°C min-1 rock temperature change is rejected, based on lack
of a sufficient empirical basis, contrasting results from acoustic emission studies, varying strength properties of different rock types, lack of data on actual strain resulting from short-term temperature variations, and lack of notable long-term weathering
The distribution, thermal characteristics and dynamics of permafrost in Tröllaskagi, Northern Iceland, as inferred from the distribution of rock glaciers and ice-cored moraines
Cold area ; Iceland ; Inventory ; Periglacial features ; Permafrost ; Photointerpretation ; Remote sensing ; Rock glacier ; Spatial distribution
active or inactive (intact), categorised them by genesis and activity, the latter independently investigated by PALSAR interferometry. Intact landforms are mainly glacigenic, occurring as moraine-derived rock glaciers or ice-cored moraines. Their dominant
reaching down to sea level. Rock glaciers at sea level may imply early deglaciation of northern Iceland.
Tropical rock coasts : Cliff, notch and platform erosion dynamics
. A consideration of temporal variations in intertidal erosion rates provides insights into the potential impacts of climate change on the erosion dynamics of rock coasts in the tropics. This paper highlights some of the interactions over time and space between
process and measurement that continue to limit our understanding of, and ability to model, the erosion dynamics of tropical rock coasts. It concludes by identifying potentially fruitful areas for future research.
Supraglacial debris supply in the Cuerpo de Hombre paleoglacier (Spanish Central System) : reconstruction and interpretation of a rock avalanche event
During the deglaciation stages of the last glacial period a rock avalanche took place on the glacier that occupied the upper sector of the Cuerpo de Hombre Valley (Sierra de Béjar). The material displaced during the avalanche fell onto the ice
carried out to quantify the stress relaxation that produced the collapse. The rock avalanche took place on a lithologically homogeneous slope with a dense fracture network. The deposit is an accumulation of large, angular, heterometric boulders
Sensitivity of frost weathering and aeolian deposition during genesis of Late Quaternary periglacial slope covers on calcareous rocks of a Muschelkalk landscape, eastern Thuringian Basin, Germany
The lithological and petrological properties of calcareous rock types are reflected by remarkably different structure, thickness and clast properties of frost shattered debris within the investigated Muschelkalk landscape as well as in chemical
and heterogeneity of periglacial loose rock cover, limestone landscapes in general seem to be vulnerable to degradation processes.
The study was conducted at one of the highest periglacial rock faces in the European Alps, the east face of Monte Rosa, Italy. Pronounced changes in ice cover and repeated rock and ice avalanche events have been documented in this rock wall since
and reveals a great volume loss in bedrock and steep glaciers in the central part of the face between 1988 and 2007. The high rock and ice avalanche activity translates into an increase in erosion rates of about one order of magnitude during recent decades.
Bibliography ; Biogenic process ; Carbonate rock ; Conceptual model ; Lichen ; Limestone ; Weathering
lifespan) and long (multiple lichen lifespans) timescales. The models suggest that the microscale biogeomorphological system of lichen-rock interaction is underpinned by non-linear dynamical system theory as it exhibits dynamical instability
Lichenometric dating of rock surfaces in the Northern Cascade Range, USA
yr periods. The revised growth curve for the study area extends the applicable range for dating rock surface in the study area to the seventeenth century, approximately 175 years longer than previous calibrated curves.