Occurrence Of Rock Glaciers Research Articles

Rock glaciers in the Gangdise Mountains, southern Tibetan Plateau: Morphology and controlling factors

Rock glaciers are linked to palaeoenvironment, water storage, sediment transport, and natural hazards. Previous rock glacier studies have been conducted in many places globally, but detailed studies have not been done in the Gangdise Mountains of the southern Tibetan Plateau (TP). In this study, 132 rock glaciers were mapped in the western, central, and eastern sectors of the Gangdise Mountains and their metrics calculated. The smallest rock glacier length in the east and the increasing trends of rock glacier density and specific area eastward reflect the effect of temperature and precipitation. The decreasing trend of mean altitude and minimum altitude of the rock glacier front towards east highlight the role of precipitation. Rock glaciers with altitudes of 5143–5651 m above sea level (asl) tend to face N, but their vector strength values decrease with altitude. Rising above 5651 m asl, rock glaciers tend to face SE. These results imply the ability of high altitude to promote rock glacier development on climatically unfavourable slopes. Bedrocks that mainly produce finer or platy debris are rarely sources of rock glacier materials. High altitude may diminish this effect. Aspect does not affect rock glacier size and shape, but rock glaciers on northern slopes have lower altitudes than those on southern slopes due to the effect of solar radiation. Welch’s test shows that rock glacier size is mainly controlled by non-lithological factors. By comparing with the previous results of the TP, it is found that increasing temperature and precipitation increase rock glacier occurrence but limit its size.

Spatial distribution of active and inactive rock glaciers and protalus ramparts in a sector of the Central Andes of Argentina

Rock glaciers and protalus ramparts are two of the main morphological features of the Central Andes in the Province of San Juan, Argentina. This sector of the Andes has one of the highest densities of occurrence of rock glaciers in the world. In this region, which has semiarid climatic characteristics, the presence of these landforms is important due to their solid state water reserves and as water resource regulators. Their occurrence is vital in several basins where, due to the lack of glaciers, debris-covered glaciers and perennial snow patches, rock glaciers are the only solid-state water reserves. However, the topo-climatic factors controlling the development and evolution of rock glaciers and protalus ramparts are not well known, which prevents an integrated management of the basins. This contribution, first, analyzes the spatial distribution of active and inactive rock glaciers and of protalus ramparts with respect to different topographic variables in the upper section of the Santa Cruz River basin. In total, 375 landforms have been inventoried, out of which 83 are active rock glaciers, 81 are inactive and 211 are protalus ramparts, covering an area of 13.09 km2 (3.03 % of the total area). The active periglacial environment belt occurs between 4000 and 4200 m a.s.l. and slopes with a southwesterly aspect have a greater development of active rock glaciers. Secondly, the evolution of such landforms is addressed. While the development of protalus ramparts does not seem to be mainly controlled by the topographic variables analyzed, the evolution of protalus ramparts in rock glaciers would be mainly controlled by elevation and aspect. Besides, there are local topo-climatic factors that contribute to the development of such landforms.

Rock glaciers in the Western and High Tatra Mountains, Western Carpathians

ABSTRACTA detailed map of rock glaciers at a scale of 1 : 40 000 is produced for the Western and High Tatra Mts., Western Carpathians, based on remotely sensed mapping. We inventoried a total of 383 rock glaciers, covering a total area of 13.84 km2. Most rock glaciers (85 %) are considered relict (without permafrost). These landforms have an average lower limit of 1684 m asl and occupy a total area of 12.50 km2. In contrast, intact rock glaciers (containing permafrost) cover a total area of 1.34 km2 and their average lower limit is located at 1986 m asl, which is 56 m above the previously suggested lower limit of discontinuous permafrost. The inventory adds new information about rock-glacier occurrence in the European high-mountain areas and improves the understanding of present and past environmental conditions in the region.

Estimating the Effect of Different Influencing Factors on Rock Glacier Development in Two Regions in the Swiss Alps

To elucidate the factors that influence rock glacier distribution, we created a rock glacier inventory for two regions in the Swiss Alps (the Albula Alps and the Glarner Alps) and identified their spatial characteristics by adding topographical and meteorological data to a GIS. We evaluated the influence of mean annual precipitation (MAP), mean annual air temperature, head wall erosion, glacier coverage, lithology, slope, aspect, elevation and snow cover on rock glacier occurrence and characteristics, taking into account the interactions between these factors. MAP, lithology and head wall erosion significantly influenced rock glacier distribution, and the interaction of precipitation and lithology seemed to play a key role. Wind-driven snow redistribution influenced rock glacier frequency on hillslopes with different aspects. Rock glaciers interact with all of the factors analysed and exhibit complex relations with their regional environments. Copyright © 2016 John Wiley & Sons, Ltd.

Characteristics and Origin of Rock Glaciers in Northern Tien Shan (Kazakhstan/Kyrgyzstan)

ABSTRACTNorthern Tien Shan is characterised by a distinct periglacial belt that contains many rock glaciers with an area of 1 km2 or more. To investigate the reason for their large size and variable occurrence, we analysed a representative subsample of the rock glaciers with respect to topographic and climatic variables. A simple permafrost model indicates that the rock glaciers originate in the zone where permafrost occurrence is very likely and some large rock glaciers flow down to elevations where permafrost is unlikely to exist outside the rock glaciers themselves. Correlation and multiple regression analyses revealed that the occurrence and characteristics of the rock glaciers can only be partly explained by the characteristics of the contributing area (e.g. its area or the headwall height). The correlation is greater with talus‐type rock glaciers than with moraine‐type rock glaciers. The climate can explain the general occurrence of rock glaciers but not their specific characteristics. It is hypothesised that the main reason for the specific distribution and characteristics of these large rock glaciers relates to the interaction with polythermal glaciers, topographic characteristics, intensive weathering and rock avalanches triggered by seismic activity. Copyright © 2014 John Wiley & Sons, Ltd.

A regional inventory of rock glaciers and protalus ramparts in the central Italian Alps

We present a regional inventory of rock glaciers (n=1514) and protalus ramparts (228) for the Lombardy region, central Italian Alps. To identify and classify the landforms we inspect three sequential air-orthophoto mosaics and a 2m-DSM, and conduct confirmatory field work. The inventory forms an empirical basis to analyze: (i) the relative contribution of hillslope (i.e., talus slopes) and glacial (i.e., moraines) sediment stores to rock glacier sediment supply; (ii) linkages between the landforms inventoried and local topographic attributes; (iii) the spatial variability of periglacial activity in relation to a parsimonious set of environmental variables (i.e., elevation, precipitation, and lithology); and (iv) the effects of the Pleistocene–Holocene climatic transition on the distribution of intact and relict landforms. This analysis reveals that the elevation of rock glacier termini can vary over 200m as a function of slope aspect. In turn, the distribution of rock glaciers among aspect categories is controlled by the structure of the valley network that promotes NW and SE exposures. Talus rock glaciers prevail numerically over the glacier-related typology, even though the latter population appears to have increased during the Holocene. Relict and intact rock glaciers have distinct spatial patterns in that the former display, on average, a 400-m elevation drop and a less clustered distribution towards northern aspects, suggesting that they have developed in more “permafrost-prone” climatic conditions. Analyzing the study region through a 27.5km-grid has been instrumental for showing that the rock glacier specific area and terminus elevation are: (i) positively correlated with terrain elevation; and (ii) negatively correlated with mean annual precipitation. As a consequence, in relation to Holocene generalized atmospheric temperature rise, intact rock glaciers have progressively disappeared from the wetter and milder portions of the central Italian Alps. Analysis of rock glacier occurrence across litho-tectonic sectors does not provide conclusive dependences and requires further analysis. This inventory, which represents a necessary preliminary step for modelling the spatial distribution of discontinuous permafrost at the regional scale, fills a critical geographic gap in the context of ongoing permafrost research in the European Alps (e.g., PermaNET).

Application of frequency ratio and logistic regression to active rock glacier occurrence in the Andes of San Juan, Argentina

This study employs statistical modeling techniques and geomorphological mapping to analyze the distribution of active rock glaciers in relation to altitude, aspect, slope, lithology and solar radiation using optical remote sensing techniques with GIS. The study area includes a portion of the Dry Andes of the Cordillera Frontal of San Juan around 30°S latitude, where few geomorphological studies have been conducted. Over 155 rock glaciers have been identified, and 85 are considered active. The relationship between the variables and the rock glaciers distribution was analyzed using the frequency ratio method and logistic regression models. The analytical results show that elevations > 3824 m a.s.l., a south-facing or east-facing aspect, areas with relatively low solar radiation, and slope between 2° and 20° favor the existence of the rock glaciers, and demonstrate that lithology and slope exert major influences.

Statistical estimation and generalized additive modeling of rock glacier distribution in the San Juan Mountains, Colorado, United States

Our goal is to quantify rock glacier abundance and analyze the topographic controls of rock glacier distribution patterns. For this purpose we use statistical estimation techniques and generalized additive models relating rock glacier occurrences to terrain attributes. Significant applied results include the ability to determine water equivalence and denudation rates. The statistical estimation of regional rock glacier abundance based on local interpretation of air photos is an efficient alternative to costly rock glacier inventories. These presence‐absence data (N = 2933) also allow us to analyze the partly nonlinear topographic controls on rock glacier distribution with generalized additive models. We apply these techniques in the San Juan Mountains (2874 km2 above 3400 m), Colorado, where we obtained a total rock glacier surface area of 70 km2 corresponding to a water equivalence in the order of 0.50–0.76 km3. Estimated rock glacier debris volumes imply postglacial denudation rates on the order of 0.5–1.1 mm yr−1 within the talus sheds of rock glaciers. The distribution model shows the nonlinear factors of local slope, slope of the contributing area, local curvature, and size of the contributing area controlling the probability of rock glacier occurrence. The model yields an area under the receiver‐operating characteristics curve of 0.91, which indicates an excellent fit. On the basis of the present results the integration of terrain attributes with remote‐sensing data will be the next step toward automatic mapping of rock glaciers in vast mountain areas.

The effect of topography, latitude, and lithology on rock glacier distribution in the Lemhi Range, central Idaho, USA

Statistical analysis of rock glaciers in the Lemhi Range demonstrates that their development and preservation is controlled primarily by annual insolation and lithology. We inspected 171 alpine valleys in the Lemhi Range using optical remote sensing techniques, digital topographic analysis, and field examination. In those valleys, we identified 48 rock glaciers and examined them for lichen cover, evidence of ice presence, specific evidence of movement, and distinctive morphological features. In addition to recording the presence or absence of a rock glacier in each alpine valley, existing rock glaciers were classified according to their morphology. Factors such as topographic shading, lithology, relief, aspect, and elevation determine the development and preservation of rock glaciers. Analysis of these factors in the Lemhi Range shows that elevation > 2600 m, a north-facing aspect (300–60°), and < 2300 h of direct sunlight per year are necessary conditions for the existence of rock glaciers in any form. The majority of alpine valleys in the Lemhi Range meet these requirements. Thus, other parameters, including topographic shading and lithology, must determine occurrence of rock glaciers in the Lemhi Range. Multivariate statistical analysis of controlling parameters demonstrates that annual insolation and latitude influence rock glacier occurrence most strongly. Whereas duration of insolation is a logical controlling factor, latitude is more enigmatic. Additional statistical analysis indicates that the latitude factor is likely a reflection of lithologic changes with latitude along the range. Lithology may affect rock glacier distribution through its effects on hydrology or air ventilation. Moreover, statistical analysis shows that rock glacier occurrence correlates with protalus lobe occurrence, suggesting that protalus lobes play a role in the genesis of rock glaciers in the Lemhi Range. Separate analysis of the classification systems shows that each morphologic class, inferred to correlate with rock glacier activity, is statistically significant and distinguishable from other classes. In addition to the effect of insolation, statistical analysis of the classification system also shows that latitude influences distribution of existing rock glacier classes independent of lithology.

Rock Glaciers of the Dalton Range, Kluane Ranges, South-West Yukon Territory, Canada

AbstractGlaciated valleys of the Dalton Range in the south-west Yukon Territory are dominated by rock glaciers identified as glacier ice-cored debris systems. The two rock glaciers studied have different amounts of deformation at present, resulting from post-formation mechanics.The primary formation of lobes of the rock glaciers resulted from periods of glacier activity in the Neoglacial, although older lobes, probably late Pleistocene in age, occur below the Neoglacial lobes. The hydrological systems of the rock glaciers have played a major role in the post-formation deformation of the land forms and the present drainage system is entirely sub-surface. The explanation for the extensive occurrence of rock glaciers in the Dalton Range is lithological as a result of the high susceptibility of the Upper Jurassic/Lower Cretaceous sediments to frost action and glacier erosion.

Rock Glaciers of the Dalton Range, Kluane Ranges, South-West Yukon Territory, Canada

Abstract Glaciated valleys of the Dalton Range in the south-west Yukon Territory are dominated by rock glaciers identified as glacier ice-cored debris systems. The two rock glaciers studied have different amounts of deformation at present, resulting from post-formation mechanics. The primary formation of lobes of the rock glaciers resulted from periods of glacier activity in the Neoglacial, although older lobes, probably late Pleistocene in age, occur below the Neoglacial lobes. The hydrological systems of the rock glaciers have played a major role in the post-formation deformation of the land forms and the present drainage system is entirely sub-surface. The explanation for the extensive occurrence of rock glaciers in the Dalton Range is lithological as a result of the high susceptibility of the Upper Jurassic/Lower Cretaceous sediments to frost action and glacier erosion.