scholarly journals Rock Glacier Dynamics by a Thermo-Elastic-Viscoplastic Constitutive Relationship

Geosciences ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 417
Author(s):  
Stefano Alberti ◽  
Luca Flessati
Keyword(s):  
Point Of View ◽  
Constitutive Relationship ◽  
High Mountain ◽  
Seasonal Temperature ◽  
Rock Glacier ◽  
Rate Dependent ◽  
Sustainable Operation ◽  
Dependent Behavior ◽  
Rock Glaciers ◽  
Basal Shear

As a result of mountain permafrost creep, rock glaciers are common features in high-altitude periglacial areas. From a practical point of view, beyond their localization and inventorying, both the monitoring and prediction of their evolution due to climate changes are crucial. One of the effects of climate change is the thickening of the basal shear zone (the portion of the rock glacier where most deformations are localized), eventually leading to the development of unexpected and unprecedented (in terms of location, magnitude, frequency, and timing) instability phenomena. These phenomena bear consequences for the understanding of landscape evolution, natural hazards, and the safe and sustainable operation of high-mountain infrastructures. Most of the studies about active rock glaciers are focused on the analysis of monitoring data, while just a few studies are focused on modeling their behavior to understand their possible further evolution. The active rock glacier response is characterized by a viscous (rate-dependent) behavior, influenced by seasonal temperature oscillations, and characterized by a seasonal transition from slow to fast. In this work, a new thermo-mechanical model based on the delayed plasticity theory and calibrated on experimental results is proposed. The model is employed to evaluate the influence of geometry and forcing (air temperature) on a real rock glacier (Murtèl-Corvatsch rock glacier) creep behavior.

scholarly journals Ice content and interannual water storage changes of an active rock glacier in the dry Andes of Argentina

2020 ◽  
Author(s):  
Christian Halla ◽  
Jan Henrik Blöthe ◽  
Carla Tapia Baldis ◽  
Dario Trombotto ◽  
Christin Hilbich ◽  
...  
Keyword(s):  
Seismic Refraction ◽  
Water Storage ◽  
Field Studies ◽  
High Mountain ◽  
Rock Glacier ◽  
Mountain Catchment ◽  
Rock Glaciers ◽  
Ice Content ◽  
Surface Ice ◽  
Water Contents

Abstract. The quantification of volumetric ice and water contents in active rock glaciers is necessary to estimate their role as water stores and contributors to runoff in dry mountain catchments. In the semi-arid to arid Andes of Argentina, active rock glaciers potentially constitute important water reservoirs due to their widespread distribution. Here however, water storage capacities and their interannual changes have so far escaped quantification in detailed field studies. Volumetric ice and water contents were quantified using a petrophysical four-phase model (4PM) based on complementary electrical resistivities (ERT) and seismic refraction tomographies (SRT) in different positions of Dos Lenguas rock glacier in the Upper Agua Negra basin, Argentina. We derived vertical and horizontal surface changes of the Dos Lenguas rock glacier, for the periods 2016–17 and 2017–18 using drone-derived digital elevation models (DEM). Interannual water storage changes of −36 mm yr−1 and +27 mm yr−1 derived from DEMs of Difference (DoD) for the periods 2016–17 and 2017–18, respectively, indicate that significant amounts of annual precipitation rates can be stored in and released from the active rock glacier. Heterogeneous ice and water contents show ice-rich permafrost and supra-, intra- and sub-permafrost aquifers in the subsurface. Active layer and ice-rich permafrost control traps and pathways of shallow ground water, and thus regulate interannual storage changes and water releases from the active rock glacier in the dry mountain catchment. The ice content of 1.7–2.0 × 109 kg in the active Dos Lenguas rock glacier represents an important long-term ice reservoir, just like other ground ice deposits in the vicinity, if compared to surface ice that covers less than 3 % of the high mountain catchment.

Creating a rock glacier inventory of the northern Nyainqêntanglha range (Tibetan Plateau) based on InSAR time-series analysis

2020 ◽  
Author(s):  
Eike Reinosch ◽  
Johannes Buckel ◽  
Markus Gerke ◽  
Jussi Baade ◽  
Björn Riedel
Keyword(s):  
Time Series ◽  
Tibetan Plateau ◽  
Time Series Analysis ◽  
Microwave Remote Sensing ◽  
High Mountain ◽  
Mountain Range ◽  
Rock Glacier ◽  
Series Analysis ◽  
Ipcc Report ◽  
Rock Glaciers

<p>The northern Nyainqêntanglha range on the southern Tibetan Plateau reaches an elevation of 7150 m and is mainly characterized by a periglacial landscape. A monsoonal climate, with a wet period during the summers and arid conditions during the rest of the year governs the landscape processes. Large parts of the mountain range are considered permafrost due to the high altitude and the associated low air temperature. Rock glaciers, which are bodies of ice-rich debris, are a typical landform. The recently published IPCC report on the cryospheres of high mountain areas highlights the sensitivity of rock glaciers to climate warming and emphasizes the importance of their study.</p><p>We study the distribution of rock glaciers of the northern Nyainqêntanglha range and our aim is to produce an inventory of active rock glaciers based on their surface motion characteristics. The lack of higher order vegetation and the relatively low winter precipitation enable us to employ Interferometric Synthetic Aperture Radar (InSAR) time-series techniques to study both seasonal and multi-annual surface displacement patterns. InSAR is a powerful microwave remote sensing technique, which makes it possible to study displacement from a few millimeters to centimeters and decimeters per year. It is thus suitable to detect sliding and creeping processes related to periglacial landscapes and permafrost conditions on the Earth’s surface. We use both Sentinel-1 (2015-2019) and TerraSAR-X ScanSAR data (2017-2019) for our analysis.</p><p>In this study we differentiate rock glaciers from the surrounding seasonally sliding slopes by their significantly higher surface creeping rates with mean velocities of 5–20 cm yr<sup>-1</sup>. We also observe that the velocity of rock glaciers is less dependent on the summer monsoon, which allows us to further differentiate between rock glaciers and other landforms. This method could potentially be used to create rock glacier inventories in other remote regions, as long as the snow cover in winter is thin enough to allow continuous InSAR time-series analysis. These rock glacier inventories are necessary to assess the effects of climate change on vulnerable high mountain regions.</p>

Distribution and morpho-thermal characteristics of rock glaciers in southern Peru: case, Cordilleras Huanzo and Chila

2020 ◽  
Author(s):  
Katy Medina ◽  
Edwin Loarte ◽  
Edwin Badillo ◽  
Hairo Leon ◽  
Francisco Castillo ◽  
...  
Keyword(s):  
Thermal Characteristics ◽  
Google Earth ◽  
High Mountain ◽  
Rock Glacier ◽  
Alos Palsar ◽  
Mountain Ranges ◽  
Thermal Range ◽  
Tropical Glaciers ◽  
The Pacific ◽  
Rock Glaciers

<p>Climate change generates significant impacts on high mountain regions, especially considering the sensitivity of tropical glaciers. However, information about rock glaciers are very scarce and there is very limited research in this field in Peru. Rock glacier concentrate mainly in the southern part of Peru where 95% of rock glaciers are located. Here we present for the first time an overview of rock glacier occurrence and characteristics in Peru.</p><p>The Cordilleras Huanzo and Chila are located in the mountain ranges in the southern region of Peru, Huanzo in the administrative region of Apurimac, Arequipa, Cusco and Ayacucho, while Chila in Arequipa. Both cordilleras extend from S 15°39'41.36" to 14°03'17.54" and W 73°24'12.55" to 71°27'113.20". For this study, remote sensing tools and geographic information system were applied, using images from Google Earth-Pro and SASPlanet, corrected DEM ALOS Palsar (12.5m), MERIT DEM (90m) and WorldClim data (1970-2000) 1 km<sup>2</sup>.</p><p>The results indicate that in the cordillera Huanzo there are 317 rock glaciers with a total area of 26.97 km<sup>2</sup> and in the cordillera Chila there are 289 rock glaciers with 17.96 km<sup>2</sup>. Concerning their activity or dynamic there are 295 intact (active and inactive) rock glaciers and 311 relict or fossil rock glaciers.</p><p>The results further indicate that rock glaciers are located in thermal ranges between -1.53°C and 3.97°C. The relict or fossil types are located in the thermal range between -1.34°C and 3.97°C, while intact types between -1.53°C and 2.56°C. The rock glaciers of the cordillera Huanzo are located at an average altitude of 4497 to 5221 m.a.s.l., while in the cordillera Chila at 4470 to 5454 m.a.s.l. The aspect is predominantly S to SW.</p><p>Rock glaciers contain ice which may represent a potential water reserve in arid regions in Southern of Peru. The greatest distribution of these resources is found in the Camana and Ocoña basins of the Pacific watershed with 38.1 km<sup>2</sup> of rock glacier area. In the Atlantic watershed, 6.8 km<sup>2</sup> of rock glaciers are located in the Alto Apurimac and Ocoña basins.</p>

scholarly journals Impact of natural parameters on rock glacier development and conservation in subtropical mountain ranges. Northern sector of the Argentine Central Andes

2016 ◽  
Author(s):  
Ana P. Forte ◽  
Cristian D. Villarroel ◽  
María Y. Esper Angillieri
Keyword(s):  
Statistical Analysis ◽  
Solar Radiation ◽  
Ratio Method ◽  
High Mountain ◽  
Special Importance ◽  
Optical Remote Sensing ◽  
Rock Glacier ◽  
Study Region ◽  
Significant Difference ◽  
Rock Glaciers

Abstract. This paper presents a detailed rock glacier inventory used in determining how the various natural parameters affect a mountain periglacial environment. This study was undertaken in a northernmost sector of the central Argentine Andes, in an area stretching between 31°02' and 31°22' S latitude. This is a high and arid subtropical region where permafrost and cryogenic processes are predominant, featuring as well as a large number of rock glaciers and associated periglacial landforms. Rock glaciers inventory was based on geomorphological characterization with optical remote sensing data and field description information. The study region covers 630 km2, with 3,25 % of this area showing 402 rock glaciers and protalus rampart features. In total, 172 rock glaciers have been identified, 48 of which are considered active. In such a sector, the protalus rampart range shows the largest landform occurrences, though fossil and inactive rock glaciers are usually larger and are developed over a larger attitudinal distribution. Based on previous studies, we have considered that the study of active rock glaciers is an effective approach to assess the current state of periglacial environment evolution. Therefore, we analysed their spatial distribution and their relationship through different variables, by resorting to statistical analysis and a frequency ratio method. The chosen natural parameters were: Lithology, Elevation, Latitude and Longitude, Aspect, Slope and Annual Potential Solar Incoming Radiation. Analytical results have demonstrated that active rock glaciers landforms lie above 3.600 m a.s.l. elevations, on 11° to 28° slopes with predominating south facing aspect and relatively low solar radiation. The statistical analysis shows that elevation, lithology and aspect are the most influencing factors for current periglacial environment development while rock glacier conservation is mainly controlled by lithology. On the study area,the annual potential solar radiation show high values but there is not any significant difference between landform and, therefore, it is scarcely influential. The research is carried out over a high mountain area where poor accessibility hindered the chances for obtaining systematic data on weather and environment. A simple and low coast methodology was used to analyse an area where no studies on rock glacier distribution had been made before. This information gains special importance because Argentina has recently instituted a national law for glacial and periglacial environment protection and conservation. Therefore, this research and its results may contribute a significant step toward knowing the number, features and distribution of rock glacier bodies lying in a scarcely studied region.

Rock glacier sediment, kinematics and geomorphometry: a study case from the Eastern Italian Alps

2021 ◽  
Author(s):  
Federica Minotti ◽  
Christian Kofler ◽  
Bernhard Gems ◽  
Volkmar Mair ◽  
Francesco Comiti
Keyword(s):  
High Mountain ◽  
Ice Melting ◽  
Italian Alps ◽  
Rock Glacier ◽  
Tauern Window ◽  
Transport Distance ◽  
Glacier System ◽  
Mountain Environments ◽  
Rock Glaciers ◽  
Unconsolidated Rock

<p>Rock glaciers are important geomorphological structures of high mountain environments and fundamental indicators for permafrost. They consist of unconsolidated rock debris – generally derived from talus or till - held together by ice, moving slowly downslope due to the gravitation in combination with uncountable freeze-thaw-cycles in the active layer. The downslope movement of rock glaciers leads to lobate structures with depressed areas as well as ridges where the sediments tend to accumulate, creating a typical surface morphology defined as "ridges and furrows". This study focuses on the analysis of one rock glacier system located in the Pfitsch/Vizze valley (South Tyrol), in the Eastern Italian Alps.  The debris in this area comprises exclusively the granitic Central Gneiss of the Tauern window. Rock glacier sediment derives from talus, consisting essentially of more or less foliated to planar angular material, which was essentially formed by frost weathering. The size and shape of sediments present at the surface of the rock glacier system were analyzed in correlation with displacement and geomorphometry, with the hypothesis that sediments shape and size at different sites across the rock glacier might relate to its past and present dynamics. The displacement analyses were carried out to quantify rock glaciers movements during the last 20 years, and the geomorphometrical characteristics were investigated to identify specific geometrical attributes that may be linked to internal ice changes.<br>Clasts analysis showed how rock glacier sediments are very heterogeneous, with dimensions being mainly determined by transport distance, and sphericity and roundness by lithology. A role of sediments characteristics on displacement rate did not turn out evident. Convexities and concavities observed on the study site are apparently created respectively by the accumulation of sediments and the collapse of the structure due to the internal ice melting. Indeed, the recent, marked increase in air temperature observed in the last decades in the Alps has likely caused an accelerated ice melting in the less protected – in terms of solar radiation – rock glaciers, as is the case for our study area. Sediments here are no longer bound by ice and have become rather unstable. Therefore, the monitoring of rock glaciers is fundamental to anticipate future changes in the type and magnitude of natural hazards originating at high elevations, as thicker layers of sediments are becoming increasingly unstable.</p>

scholarly journals Ice content and interannual water storage changes of an active rock glacier in the dry Andes of Argentina

2021 ◽  
Vol 15 (2) ◽  
pp. 1187-1213
Author(s):  
Christian Halla ◽  
Jan Henrik Blöthe ◽  
Carla Tapia Baldis ◽  
Dario Trombotto Liaudat ◽  
Christin Hilbich ◽  
...  
Keyword(s):  
Water Content ◽  
Water Storage ◽  
Shallow Groundwater ◽  
High Mountain ◽  
Rock Glacier ◽  
Mountain Catchment ◽  
Refraction Tomography ◽  
Rock Glaciers ◽  
Ice Content ◽  
Surface Changes

Abstract. The quantification of volumetric ice and water content in active rock glaciers is necessary to estimate their role as water stores and contributors to runoff in dry mountain catchments. In the semi-arid to arid Andes of Argentina, active rock glaciers potentially constitute important water reservoirs due to their widespread distribution. Here however, water storage capacities and their interannual changes have so far escaped quantification in detailed field studies. Volumetric ice and water content was quantified using a petrophysical four-phase model (4PM) based on complementary electrical resistivity tomography (ERT) and seismic refraction tomography (SRT) in different positions of the Dos Lenguas rock glacier in the upper Agua Negra basin, Argentina. We derived vertical and horizontal surface changes of the Dos Lenguas rock glacier, for the periods 2016–2017 and 2017–2018 using drone-derived digital elevation models (DEMs). Interannual water storage changes of −36 mm yr−1 and +27 mm yr−1 derived from volumetric surface changes for the periods 2016–2017 and 2017–2018, respectively, indicate that significant amounts of annual precipitation can be stored in and released from the active rock glacier. Geophysical results show heterogeneous ice and water content with ice-rich permafrost and supra-, intra- and sub-permafrost water pathways at the end of the thaw period. Active layer and ice-rich permafrost control traps and pathways of shallow groundwater and thus regulate interannual storage changes and water releases from the active rock glaciers in the dry mountain catchment. The ice content of 1.7–2.0 × 109 kg in the active Dos Lenguas rock glacier represents an important long-term ice reservoir, as do other ground ice deposits in the vicinity, if compared to surface ice that covers less than 3 % of the high mountain catchment.

Social Justice and Critical/Performative Communicative Pedagogy

2011 ◽  
Vol 4 (1) ◽  
pp. 21-34 ◽  
Author(s):  
John T. Warren
Keyword(s):  
Qualitative Research ◽  
Social Justice ◽  
Classroom Interactions ◽  
Point Of View ◽  
Constitutive Relationship ◽  
Just World ◽  
The World ◽  
Analytical Point ◽  
Embodied Pedagogy

Through narratives and critical interrogations of classroom interactions, I sketch an argument for a co-constitutive relationship between qualitative research and pedagogy that imagines a more reflexive and socially just world. Through story, one comes to see an interplay between one's own experiences, one's own desires and one's community — I seek to focus that potential into an embodied pedagogy that highlights power and, as a result, holds all of us accountable for our own situated-ness in systems of power in ways that grant us potential places from which to enact change. Key in this discussion is a careful analytical point of view for seeing the world and a set of practices that work to imagine new ways of talking back.

Dynamic evolution of shear rate-dependent behavior of rock discontinuity under shearing condition

2021 ◽  
Vol 28 (6) ◽  
pp. 1875-1887
Author(s):  
Lin-lin Gu ◽  
Zhen Wang ◽  
Feng Zhang ◽  
Fei Gao ◽  
Xiao Wang
Keyword(s):  
Shear Rate ◽  
Dynamic Evolution ◽  
Rock Discontinuity ◽  
Rate Dependent ◽  
Dependent Behavior

scholarly journals Observations on a Debris-Covered Polar Glacier “Whisky Glacier”, James Ross Island, Antarctic Peninsula, Antarctica

1987 ◽  
Vol 33 (115) ◽  
pp. 300-310 ◽  
Author(s):  
T.J.H. Chinn ◽  
A. Dillon
Keyword(s):  
Antarctic Peninsula ◽  
Rock Glacier ◽  
Freezing Front ◽  
Extensive Area ◽  
Free Zone ◽  
Rock Glaciers ◽  
James Ross Island ◽  
Polythermal Glacier ◽  
Powerful Mechanism

Abstract“Whisky Glacier” on James Ross Island, Antarctic Peninsula, comprises anévéand clean ice trunk surrounded by an extensive area of debris-covered ice resembling a rock glacier. The debris-free trunk of the glacier abuts abruptly against the broad, totally debris-covered tongue at a number of concentric zones where debris-laden beds crop out at the surface in a manner similar to the “inner moraine” formations of many polar glaciers.Ice structures and foliation suggest that “Whisky Glacier” is a polythermal glacier which is wet-based under the debris-free zone, and dry-based under the debris-covered zone. It is surmised that the glacier sole crosses the freezing front close to where the basal debris beds are upwarped towards the surface. Here, basal water is confined, and freezes to the under side of the glacier in thick beds of regelation ice which are uplifted to the surface along with the debris-laden beds. Ablation losses effectively cease beneath the blanket of debris covering the tongue.The transition from wet-based to dry-based conditions at the glacier sole is a powerful mechanism for entraining debris into a glacier and, in the case of “Whisky Glacier”, for lifting debris to the surface. It is suggested that this may be a mechanism for forming some polar rock glaciers.

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