Talus Rock Glaciers Research Articles

Talus rock glaciers in the Cairngorm Mountains

ABSTRACT Although several relict talus rock glaciers (TRGs) of Lateglacial age have been identified in the British Isles, all have been refuted by some authors and their absence attributed to the lack of permafrost. The evidence provided by palaeoclimatic reconstructions and periglacial features, however, implies that Lateglacial permafrost was present throughout Scotland during the Loch Lomond Stade (LLS; ∼12.9–11.7 ka). Across much of the Scottish Highlands, the absence of Lateglacial TRGs is attributable to occupation of potential sites by glaciers during the LLS. In the Cairngorms, however, where limited snowfall at that time left some corries glacier-free, there is convincing evidence for TRG formation. Three examples illustrating different degrees of TRG development are described; all occur at high-level (>840 m) sites that remained glacier-free during the LLS, and all lack plausible alternative explanations. The apparent scarcity of relict TRGs even in the Cairngorms may reflect the development of ‘cold’ permafrost and/or a lengthy time lag between permafrost development and the accumulation of a sufficient volume and thickness of ground ice to permit permafrost creep and deformation of an overlying mantle of bouldery debris. In consequence, relict TRGs may occur only at favourable high-level sites where permafrost developed earliest.

Decoupled kinematics of two neighbouring permafrost creeping landforms in the Eastern Italian Alps

AbstractAn overall acceleration of rock glacier displacement rates in the Alps has been observed in recent decades, with several cases of destabilization leading to potential geomorphological hazards. This behaviour has been attributed to the rising permafrost temperature, induced by atmospheric warming and regulated by thermo‐hydrological processes. Landforms derived from the interaction of glacier remnants and permafrost are widespread in mountain areas, but are less studied and monitored than talus rock glaciers. This work presents a comparative study of a talus rock glacier and a glacial‐permafrost composite landform (GPCL) in the Eastern Italian Alps. The two landforms are only 10 km apart, but have rather different elevation ranges and main slope aspects. The kinematics and ground thermal conditions were monitored from 2001 to 2015 along with geomorphological surveys, analyses of historical maps and remote sensing data. The dynamic behaviour of the rock glacier was similar to the majority of monitored rock glaciers in the Alps, with an acceleration after 2008 and a velocity peak in 2015. In contrast, the GPCL had a nearly unchanged displacement rate during the observation period. Statistical analyses of kinematic vs. nivo‐meteorological variables revealed a dynamic decoupling of the two landforms after 2008 that corresponds with increased winter snow accumulation. Although the kinematics of both landforms respond to ground surface temperature variations, the collected evidence suggests a different reaction of ground surface temperature to variations in the precipitation regime. This different reaction is likely due to local topo‐climatic conditions that affect snow redistribution by wind. The different reactions of the two systems to the same climatic forcing is likely a legacy of their different origins. GPCL dynamics result from interaction of permafrost and residual glacial dynamics that are associated with possible peculiarities in the internal/basal meltwater circulation, whose future response is uncertain and requires improved understanding. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.

Southern Carpathian rock glaciers: Inventory, distribution and environmental controlling factors

Rock glaciers are valuable diagnostic landforms indicating permafrost creeping during their genesis and activity. Based on the analysis of high quality air-orthophoto and field work, a first polygon-based inventory of rock glaciers from the Southern Carpathians has been elaborated. In total, 306 rock glaciers were included in the inventory comprising 79 debris and 227 talus rock glaciers. Most of these landforms were classified as relict (258), while only 48, covering 2.81km2, were considered intact. The size of rock glaciers, considered as a proxy for past environmental conditions, and the relationships with the predictor variables (lithology, aspect, contributing area, geographic coordinates, elevation and slope range) were analysed using bivariate statistics, analysis of variance (ANOVA) and various post hoc tests. The statistical analysis revealed that the rock glaciers occurring in the highest mountain ranges in areas composed of granites and granodiorites are considerably larger than the others, because their duration of activity is greater. Strong dependences between rock glacier size and other topographic attributes (contributing area, aspect and slope range) were also confirmed. The rock glacier distribution in the Southern Carpathians is clearly controlled by topography, lithology and debris availability. The abundance of rock glaciers increases with altitude, but their size decreases slightly. In mountain units where granites and granodiorites predominate (Retezat and Parâng Mountains), the density of rock glaciers and the mean specific area covered by these spectacular landforms are considerably higher than in other areas. The higher continentality effects of the Southern Carpathians enabled the formation of rock glaciers at substantially lower elevations than in the Alps. The mean altitude of intact rock glaciers front, which could be used as a morphological indicator of discontinuous permafrost, is located at 2088m.

Investigation on protalus ramparts in the Swiss Alps

Abstract. The origin and classification of landforms denominated as "protalus ramparts" in the scientific literature is a problem that is far from being resolved. The main objective of this contribution is to support a permafrost-related definition of protalus ramparts. If we consider the Alpine framework, protalus ramparts are generally very rare landforms; by contrast, the Alpine periglacial belt is characterised by a large diffusion of talus slopes and talus rock glaciers. The investigations carried out in six sites of the Valais Alps (Switzerland) allow eight major "diagnostic criteria" to be presented that help to define protalus ramparts in Alpine environments and that support the permafrost-related genesis of most of them. The major source of controversy is related to the use of the term protalus rampart to designate both a nivo-gravitational landform (also called "pronival ramparts") and a permafrost-related landform. All the considerations presented here allow an active protalus rampart to be defined simply as a (small) active talus rock glacier.

Los glaciares rocosos de Sierra Nevada y su significado paleoclimático : Una primera aproximación

This paper provides an inventory of 36 rock glaciers located in the western part of Sierra Nevada mountains. All the forms fall in the category of talus rock glaciers. All the rock glaciers were classified as relict except the rock glacier situated in Corral del Veleta which still preserves certain amount of ice in its interior. The cartographic information was included and analyzed within a Geographical Information System (GIS) and the results show that the rock glaciers in Sierra Nevada are located between 2460 and 3360 m a.s.l., on slopes of 21º on average that receive low amounts of solar radiation, although due to particular wind direction and snow accumulation conditions in Sierra Nevada, there is a significant number of rock glaciers lying on the southern slopes. The present altitudinal distribution of rock glaciers suggests average temperatures 6º C lower than today at the time of their initiation. Two rock glaciers as well as one abrasion surface were sampled and dated using the 36Cl cosmogenic exposure method. The results show that the rock glaciers developed immediately after the Pleistocene glaciers retreated (14 – 15 ka) and were still active throughout the first part of the Holocene (8-7 ka). The rock glacier situated in the Corral del Veleta is a recent example of rock glacier formation in a deglaciated environment during the final phase of the Little Ice Age.

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).

A preliminary inventory of periglacial landforms in the Andes of La Rioja and San Juan, Argentina, at about 28°S

The Cerro El Potro and nearby mountain chains belong to the Andean Frontal Cordillera (28°S). Cerro El Potro is a glaciated mountain that is surrounded by huge valleys both on its Chilean and Argentinean flanks. Its southern limit is a steep rock wall towards the trough-shaped Río Blanco valley in Argentina, with a wide valley floor. The other sides of the mountain are characterized by well-developed Pleistocene cirques. The predominant landforms in this area have been shaped in a periglacial environment superimposed on an earlier glacial landscape. It is a region with abundant rock glaciers, a noteworthy rock glacier zone, but nevertheless, it is a relatively little known area in South America. In this preliminary inventory, the landforms surveyed were mainly gravitational in origin, including valley rock glaciers, talus rock glaciers, debris cones, landforms originated by solifluction processes and talus detrital sheets on mountain sides. Ancient moraine deposits have been found on the sides of the main rivers that cross the area form west to east, including the Blanco and Bermejo rivers. Present day fluvial activity is limited, and restricted to these main rivers. In this area of glacial valleys and small cirques, there are small lakes and other water bodies, grass covered patches and zones with high mountain vegetation. Present day glacial activity is restricted to the highest part of the area, above 5500 m a.s.l., mainly in the Cerro El Potro (5879 m) where a permanent ice field exists, as well as small mountain glaciers.

Relict rock glaciers as indicators of Mediterranean palaeoclimate during the Last Glacial Maximum (Late Würmian) in northwest Greece

AbstractRelict rock glaciers have been identified and mapped in the high cirques of Mount Tymphi, in the Pindus mountains of northwest Greece. They are periglacial forms and represent the most recent cold‐stage landforms in an area that displays widespread evidence of Pleistocene glaciation. It is likely that these features formed during the Last Glacial Maximum (Late Würmian) as talus rock glaciers, and beneath small cirque glaciers as debris rock glaciers. Comparisons with modern rock glacier–climate relationships suggests mean annual temperatures of ca. 8–9°C lower than present at their time of formation. This temperature reconstruction is in good agreement with recent palaeoclimatic reconstructions for the northern Mediterranean based on a general circulation model. Moreover, as rock glaciers are typical of cold and relatively dry mountain regions, their presence is consistent with palaeobotanical and lake‐level data suggesting a cold and relatively dry climate for the Last Glacial Maximum in Greece. However, the presence of small cirque glaciers above some rock glaciers suggests that although precipitation must have been low enough to preclude glacier extension down to lower altitudes, it was not so low as to inhibit glacier formation entirely. Copyright © 2003 John Wiley & Sons, Ltd.

Características geomorfológicas de un sistema de glaciares rocosos y de su sustenatción en Chile semiárido

Se estudia un sistema de glaciares rocosos en un valle alto andini del semiárido de Chile, en la cuenca del Río Limarí , con el propósito de identificar las distintas formas presentes, su dinámica, las relaciones con el entorno y los diferentes estadios evolutivos. Se reconoce formas glaciales y periglaciales, en las que se inscriben algunas de las fases evolutivas de los glaciares rocosos. De estos últimos, las tipologías reconocidas corresponden a un glaciar rocoso inactivo con forma de lengua, y a glaciares rocosos de talud simples, ondulados y lobulados. Se establece que los procesos periglaciales de las vertientes son un factor muy importante en la dinámica actual de los sistemas de glaciares rocosos en función del constante aporte de detritos. El conjunto de formas analizadas está morfogeneticamente ligado tanto a procesos glaciales en su origen como a periglaciales en su evokución, dando cuenta de un sistema de complejo que constituye un continuum geomorfológico. El grado de actividad del sistema denota una marcada estacionalidad, debido al breve y poco riguroso período invernal y al prolongado y temperado período estival de la alta montaña de los Andes de la región semiárida chilena.

Rock glaciers in the South Shetland Islands, Western Antarctica

Rock glaciers are found in the peripheral regions of Antarctica particularly in the Antarctic Peninsula region. Study of these features is relevant for the palaeoenvironmental reconstruction of maritime Antarctica because they are indicators of permafrost and periglacial conditions. This paper reports and analyzes the results of an inventory of rock glaciers and protalus lobes in the South Shetland Islands. Nine rock glaciers and eleven protalus lobes have been identified. All of them are located in recently deglaciated zones between 300 m a.s.l. and sea level and they cover an area of 497×103 m 2. Tongue-shaped rock glaciers are more common than lobate types, being in general of medium and small sizes. They are talus rock glaciers (55%) and debris rock glaciers (45%), according to the genetic classification. The lack of a preferred orientation suggests that there is no significant microclimate control on their distribution. They are related to particular morphodynamic situations. Estimated annual velocities, based on relationships with raised beaches and transported debris volumes, range between 2.4 and 97 cm year −1, within the ranges reported for other rock glaciers. Three groups of rock glaciers can be recognised: (a) those immediate postdating the last major ice recession, (b) rock glaciers younger than 2000 years BP but pre-dating the Little Ice Age (LIA), and (c) rock glaciers formed during the LIA.

The relationship between climate and rock glacier distribution in the ben ohau range, new zealand

Landforms of ice and debris transport marginal to the glacierized zone of the Southern Alps, New Zealand, have been classified into debris‐covered glaciers, cirque floor lobes, and talus‐derived rock glaciers. Mapping of fossil and active landforms reveals a zonation within the Ben Ohau Range in terms of both landform type and activity status. The dominant distinction of active forms is between relatively ice‐rich forms (glacial origins) in the humid north and relatively debris‐rich forms (periglacial origins) in the more arid south. A secondary altitudinal zonation distinguishes currently or recently active forms at high elevations from fossil forms at lower elevations. Estimates of mean annual precipitation and of the altitude of the –2°C mean annual isotherm indicate that glaciers and active talus rock glaciers are located within the climatic boundaries identified for the European Alps. However, many fossil forms also occur within these boundaries where cirques are broader and shallower. These findings confirm earlier suggestions that permafrost occurs in the Southern Alps, but is restricted to a narrow zone above 2000 m. The study demonstrates the importance of relative ice‐to‐debris fluxes in determining the developmental pathways of landform genesis over both space and time.

Talus rock glaciers in Scotland: Characteristics and controls on formation

ABSTRACT Talus rock glaciers produced by creep of internal ice are common in mountains underlain by permafrost. In Scotland, relict talus rock glaciers of inferred Loch Lomond Stadial age are rare, despite widespread former permafrost. In part this reflects occupation of favourable sites by glacier ice. Outside the glacierized area, rock glacier formation was constrained by debris thickness. The debris in most of the rock glaciers studied appears to have been supplied by rock-slope failure, suggesting that steady-state rockfall accumulation was generally insufficient to initiate rock-glacier creep.

Permafrost creep and rockglaciers

AbstractActive rockglaciers are discussed as the visible expression of creep of alpine or mountain permafrost. They are mainly formed below talus slopes (talus rockglaciers) and below lateral and terminal moraines (debris rockglaciers). Rockglaciers prefer continental, comparatively dry, winter‐cold mountains. They are not well developed in high maritime and humid tropical mountains. Active rockglaciers are indicators of active mountain permafrost and, thus, of great geoecological information value.