bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal gradients and rock weathering at low temperatures: Some simulation data
Authors: Hall Kevin , Hall Alida 
Published: February 2007

AbstractThe heating of rock by insolation during subzero air temperatures may cause thermal stresses within that rock. The values of Δt may be such that fracturing due to thermal shock may occur. The uneven heating of a rock body may cause buttressing of the heated faces such that thermal stresses are accentuated. Upon removal of the heat source, rapid cooling may occur and values of Δt may be sufficient to cause thermal shock.Replications of these thermal stresses may lead to fatigue and failure. The zone within which these stresses may occur is also one within which freeze‐thaw can take place if water is present. It is suggested that thermally induced fracturing of rock in cold environments may be a significant but underrated process. Thermal results of laboratory simulation experiments are presented during which values of Δt = >500ºC/h occurred for short periods.
Genesis of massive ice at ‘Ice Mountain’, Yenesei River, Western Siberia, according to results of gas analyses
Authors: Arkhangelov A. A. , Novgorodova E. V. 
Published: February 2007

AbstractAnalyses of the gas composition of bubbles in the massive ice at Ice Mountain, made for the first time, enable one to conclude that the origin of ice is glacial.O2, H2, CO2, N2, He and CH4 were determined. Our genetic proof is based on the principally different bio‐ and chemical gas contents in intrasedimental and surface ice. That is why we also deduce the data on the ice of clear genesis: modern glaciers and injection ice.Gas composition seems to be an important criterion of ice genesis and this method should be applied to other massive ice bodies of unknown origin.
Weathering by segregation ice growth in microcracks at sustained subzero temperatures: Verification from an experimental study using acoustic emissions
Authors: Hallet B. , Walder J. S. , Stubbs C. W. 
Published: February 2007

AbstractIn a continuing effort to better understand the frost‐induced breakdown of rock, experiments were designed specifically to assess a theoretical model of crack propagation due to segregation ice growth in water‐saturated rocks with interconnected cracks (Walder and Hallet, 1985). A rectangular block of Berea Sandstone was frozen unidirectionally while the temperature and acoustic emissions, which reflect microfracture propagation events, were monitored. Acoustic emissions were counted and approximately located as a function of time and temperature while the rock sample was subjected to a fixed temperature gradient.The experimental results indicate considerable frost damage to sandstone due to ice growth in an open system with migration of water to freezing centres much as segregation ice grows in soils, as has been previously suggested. Freezing‐induced microfracture propagation events are not associated with the freezing temperature, which is about —0.2 ºC for Berea Sandstone; most of the fracture activity occurs at distinctly lower temperatures, between —3 ºC and —6 ºC, in accord with our theoretical predictions. Such microfracturing does not require freeze‐thaw cycling or even falling temperatures; temperatures were held constant but spatially nonuniform for the duration of most experiments.Through a series of experiments other aspects of the model are being tested and the influence of lithology is being examined. Diverse geomorphic implications of this model are discussed because it offers attractive alternative insights to those available with the conventional view of frost weathering. A plea is made to strive towards a more fundamental and unified view of frost weathering and related phenomena.
Frost weathering of rocks in the presence of salts‐a review
Authors: Williams R. B. G. , Robinson D. A. 
Published: February 2007

AbstractIn many temperate and cold regions, rocks containing salt in solution are subject to frost action. Although the salts depress the freezing point of water, their most common effect at subzero temperatures is to increase the intensity of rock breakdown. Different mechanisms to explain why salts often accelerate frost weathering are outlined and their possible applicability to the weathering of different rocks undergoing different frost regimes is assessed. It is concluded that, because different salt solutions exhibit different crystallization behaviour at subzero temperatures, resulting in varied proportions of water, ice and salt crystals, more than one mechanism is likely to be responsible for rock breakdown. The importance of the different mechanisms will vary with the composition and strength of the salt solution, the temperature regime, the rock type and other factors.
A solifluction meter for permafrost sites
Authors: Lewkowicz Antoni G. 
Published: February 2007

AbstractA solifluction meter that measures soil movements at eight levels in the active layer is described. Anchored in permafrost, the meter transforms mechanical movement of wooden blocks attached to flexible racks into changes in the electrical resistance of potentiometers. Solifluction can be monitored continuously with a data‐logger or manually at intervals when visiting field sites. Preliminary results from meters installed on the Fosheim Peninsula, Ellesmere Island, illustrate frost creep, with heave continuing at ground temperatures between −25°C and −30°C, and summer movements of the active layer in response to thaw consolidation and precipitation.
Dynamics of rock glaciers of the Northern Tien Shan and the Djungar Ala Tau, Kazakhstan
Authors: Gorbunov Aldar P. , Titkov Sergei N. , Polyakov Victor G. 
Published: February 2007

AbstractOver 1500 active rock glaciers have been identified in the Northern Tien Shan and the Djungar Ala Tau, Kazakhstan. Studies of the dynamics of six near‐glacier rock glaciers for 15–60 years show rates of movement in the main body of the rock glacier of 0.16–14.0 m/y. These also vary with time. Factors involved include climatic change, changes in ice content in the source area, flow of glacial meltwater through the rock glacier, changes in gradient of the underlying surface and changes in width of the valley through which it moves.
Interactions and relations between mountain permafrost, glaciers, snow and water
Authors: Harris Stuart A. , Corte Arturo E. 
Published: February 2007

AbstractThere are problems in determining the amount of precipitation at a given site in mountain permafrost areas, because snow can be redistributed by wind or avalanches. Both snow and rain greatly affect permafrost distribution. Surface soil conditions also affect permafrost distribution. Dry blocky surfaces, peaty soils and soils with a thick organic mat tend to favour permafrost development. Active layers are deepest on dry mineral soils at low latitudes. Moist soils have thin active layers which exhibit the zero curtain effect during freezing and thawing. Meteoric H2O enters permafrost in response to thermal gradients. The H2O content may reach 80% by volume in its upper layers in some rock glaciers. In Kazakhstan a perched water table occurs above the thawing front in the active layer and provides a reliable supply of water to plants, so that the permafrost lands have a lush meadow tundra in summer. The physical and chemical properties of the discharge from mountain permafrost areas can be used to differentiate it from glacial discharge and groundwater. There is an antipathetic relationship between the lower limit of permafrost and the equilibrium line on glaciers. Gorbunov's Continentality Index is the only system for classifying the climate of mountain permafrost areas that indicates their great climatic variability.
Permafrost creep and rockglaciers
Authors: Barsch Dietrich 
Published: February 2007

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.
Alpine periglacial landforms of eastern North America: A review
Authors: Clark G. Michael , Schmidlin Thomas W. 
Published: February 2007

AbstractPermafrost and periglacial features occur at high elevations in the mountains of New England (Presidential Range), Gaspésie, Western Newfoundland and Labrador. Both active and inactive patterned ground features have been reported together with block fields and felsenmeer. Problems relate to the complex deglaciation histories of the areas in question, the possibility that nunataks existed during the last glaciation, and the role of cold‐based versus warm‐based ice in landform preservation. There is need for more research on periglacial features and deposits in the alpine zone of eastern North America.
Active rock glaciers and the lower limit of discontinuous alpine permafrost, Khumbu Himalaya, Nepal
Authors: Jakob Matthias 
Published: February 2007

AbstractSeismic refraction studies were carried out on four rock glaciers in the Khumbu Himalaya near the Poklade massif (27°55′ N, 86°50′ E) and its surroundings. P‐wave velocities at profiles on southeast‐facing slopes indicate that the lower limit of discontinuous alpine permafrost is between 5560 m and 5360 m a.s.l. On west‐facing slopes the lower limit varies between 4959 m and 5050 m a.s.l. These values agree with elevations of active rock glacier termini.
Rock glaciers and periglacial phenomena in the southern Carpathians
Authors: Urdea Petru 
Published: February 2007

AbstractGlacial and periglacial phenomena in the southern Carpathians are an undoubted reality. Climatic conditions and lithology favour the existence of rock glaciers, block fields, cryoplanation terraces, ploughing blocks and solifluction. The highest frequency and the most complex of rock glaciers are found in granites and granodiorites within northerly cirques and valleys of the Paring and Retezat Mountains, whereas less frequent and predominantly embryonic, protalus rampart‐type forms occur in epimetamorphic precrystalline schists. Water temperatures below 2 °C of the springs emerging in summer from the fronts of some rock glaciers point to local permafrost conditions possibly still existing today.
High‐latitude rock glaciers: A case study of forms and processes in the Canadian arctic
Authors: Evans David J. A. 
Published: February 2007

AbstractRock glaciers in the Phillips Inlet/Wootton Peninsula area of northwest Ellesmere Island are of the talus‐foot or valley‐side type and all lie below 180 m a.s.l. The rock glaciers are located predominantly below extensive bedrock gullies at the base of steep fiord and U‐shaped valley walls. Two types of rock glacier of talus‐foot type exist in the area. (1) Glacier ice‐cored rock glaciers occur above marine limit and coincide with projected margins of former glaciers which are demarcated by the use of glacimarine and sea level evidence. Because these rock glaciers are discontinuous and have not been carried down flow line, they probably relate to catastrophic slope failures over stagnant ice. (2) Permafrost‐related rock glaciers lie either below marine limit, especially in areas of heavy glacierization by floating glaciers, or in areas of former ice‐dammed lakes. The fine‐grained sediments appear to provide a deformable substrate and/or the perfect medium for the development of substantial interstitial ice. The initiation of all rock glaciers in this environment relates to the palaeogeography of the last glaciation; glacier ice‐cored (glacial) rock glaciers occur at former glacier margins and permafrost‐related (periglacial) rock glaciers occur below the marine limit associated with those glacier margins.
Investigations of cryogenic weathering in Europe and Northern Asia
Authors: Konishchev V. N. , Rogov V. V. 
Published: February 2007

AbstractRecent Russian investigations into cold climate (i.e. cryogenic) weathering are reviewed. Data obtained from both experimental and field studies upon rock breakdown are summarized and values of cryogenic stability and cryogenic contrast are presented for different mineral assemblages and for rocks of different ages. Unconsolidated ice‐rich sediments are emphasized.
Permafrost changes in Europe during the last glacial
Authors: Vandenberghe J. , Pissart A. 
Published: February 2007

AbstractReconstruction of former permafrost is based on specific indicators which represent relics of features developed above or within the permafrost. Their interpretation in terms of genesis and (palaeo)climatic significance, however, is in some cases still under debate. Previously the reconstruction of the periglacial environment in Europe was limited to permafrost mapping during the coldest time of the last glaciation. Today a much more refined evolution of the palaeoclimate of the last glacial has been established, thanks to a considerable increase in registered periglacial indicators, a better understanding of the corresponding climate conditions, and more accurate and reliable dating of the periglacial phenomena.
Permafrost zonation in Russia under anthropogenic climatic change
Authors: Nelson Frederick E. , Anisimov Oleg A. 
Published: February 2007

AbstractWarming induced by the hypothesized greenhouse effect will have profound consequences for permafrost distribution throughout the high‐latitude regions of the globe. Two scenarios of climate change based on the palaeo‐reconstruction method widely employed by Russian scientists were used in conjunction with a model that produces zonal maps of permafrost distribution. Changes associated with both 1.2°C and 2.0°C warming of the mean global temperature are amplified in the high latitudes, which results in the potential for a large reduction of the area underlain by continuous permafrost. Thermokarst development is likely to be particularly acute in the West Siberian plain, where the climate model suggests that conditions will become marginal for the maintenance of permafrost.
Mountain permafrost and climatic change
Authors: Haeberli W. , Guodong Cheng , Gorbunov A. P. , Harris S. A. 
Published: February 2007

AbstractPerennially frozen slopes occur in many mountain ranges of the world. Ice‐rich debris or morainic material especially exist under subcontinental to continental‐type climatic conditions with elevated glacier equilibrium lines. Such supersaturated mountain permafrost exhibits pronounced creep movements, thereby forming large numbers of rock glaciers. Reconstructions of late‐glacial palaeotemperature and palaeoprecipitation using combined glacier/permafrost studies reveal dramatic changes in permafrost belts and in the periglacial environments of mountain areas during the pronounced late‐glacial warming. As a consequence of atmospheric warming during the first half of the twentieth century, the lower boundary of mountain permafrost distribution in various mountain ranges such as the Alps may have shifted in altitude, causing local degradation of formerly frozen slopes. Continued or even accelerated future warming is likely to induce further retreat and degradation of high‐altitude permafrost.
Coastal dune development in a thermokarst environment: Some implications for environmental reconstruction, Tuktoyaktuk Peninsula N.W.T.
Authors: Ruz Marie‐Hélène 
Published: February 2007

AbstractThe landscape of the Tuktoyaktuk Peninsula coastal plain, Northwest Territories, has been strongly affected by thermokarst processes. Along thermokarst lakes developed in glacio‐fluvial sands lake‐shore dunes are common. Their formation seems related to complete or partial lake drainage. During the Holocene the rise of relative sea level has induced the submergence of the coastal plain that extended offshore of the present‐day coastal lowlands. Today coastal retreat rates in excess of 1 m/yr result in thermokarst lakes breaching and landward migration of spits and barrier‐islands. A unique type of coastal dune has been observed along two coastal sections. Late Holocene lake‐shore dunes are eroded alongshore and capped by modern coastal dunes. These coastal dunes developed in a thermokarst environment are indicators of lake drainage probably induced by late Holocene sea level rise.
Fabric analysis of rock glacier debris mantles, La Sal Mountains, Utah
Authors: Nicholas Joseph W. 
Published: February 2007

AbstractMacrofabrics of rock glacier debris mantles display significant variation even among similar microtopographic features. Fabrics of longitudinal ridges of La Sal rock glaciers are equally divided between cluster and girdle distributions. In some cases, fabric patterns resemble those of lahars, implying that the flow mechanics of rock glaciers bears some similarity to that of large‐scale debris flows. Shear zones are found at the margins of many longitudinal ridges, and in at least one case these zones separate the rock glacier from a pair of bounding ridges that resemble debris‐flow levees. Other sites display fabric patterns that indicate that the dominant processes are dry creep of the open‐matrix debris mantle. Weak fabrics are found at sites where rockfall inputs occur on a low‐angle surface, or where a debris mantle is undergoing passive transport by a moving core.
Structures Sédimentaires d'un Cǒne de Flots de Débris (Vars, Alpes Françaises Méridionales)
Authors: Bertran Pascal , Texier Jean‐Pierre 
Published: February 2007

AbstractDes coupes réalisées dans un cǒne de flots de débris alpin ont mis en évidence une stratification, dont la physionomie varie en fonction de la distance à l'apex du cǒne. Dans les fadès proximaux, la stratification est discontinue et constituée par des lentilles de cailloutis ouvert dans un diamiction. L'origine des cailloutis est discutée à la lumière des figures sédimentaires observées dans un flot récent. La partie distale du cǒne est caractérisée par l'interstratification de lobes, de colluvions et de paléosols. Stratification, fabriques et microstructures sont significativement différentes de celles produites par la solifluxion et peuvent constituer des figures diagnostiques pour reconnaǐtre les dépǒts fossiles.
Permafrost distribution in the southern circumpolar region and its relation to the environment: A review and recommendations for further research
Authors: Bockheim James G. 
Published: February 2007

AbstractBecause of basal melting beneath the massive Antarctic ice sheet, permafrost probably comprises less than 25% of the Southern Circumpolar Region (c. ≥ 50°S latitude). Permafrost is pervasive in ice‐free areas of Antarctica and its offshore islands but is lacking in the sub‐Antarctic islands, except possibly at the higher elevations. Based on limited data, the thickness of permafrost ranges from 100 to 1000m in ice‐free areas of Antarctica. The thickness of the active layer ranges between 50 and 150 cm in the Antarctic islands and maritime East Antarctica and 15 and 50 cm in interior Antarctica. Ground ice is restricted to rock glaciers and ice wedges; the rock glaciers, palsa and thermokarst reported in some areas originate from ice‐cored drift and not permafrost. Active and inactive patterned ground occurs throughout the region. Whereas sorted circles, nets, and stripes are common in the Antarctic islands and in maritime East Antarctica, ice‐ and sand‐wedge polygons are prevalent in ice‐free valleys of Antarctica. Altiplanation terraces may exist in the Antarctic islands and in maritime East Antarctica; however, landforms in interior Antarctica are controlled more by salt weathering than by cryogenic processes. Based‐on the presence of inactive rock glaciers, gelifluction lobes, and large‐scale patterned‐ground features, permafrost was probably present in the sub‐Antarctic islands during the last glaciation. Recommendations are made for future work in the region.
Enseignements de i'étude Morphosédimentaire de la Grézière de Tilly‐sur‐Meuse
Authors: Harmand D. , Deshaies A. Weisrock Et M. 
Published: February 2007

AbstractLa grézière de Tilly‐sur‐Meuse, située sur le versant ouest de la vallée de la Meuse lorraine, à 20 km au sud de Verdun, présente plusieurs cǒnes surbaissés coalescents de grèze, euxměmes constitués de trois formations. Les trois formations sont constitutées de la base vers le sommet par: des grèzes inférieures, jaunes et à litage centimétrique, coïncidant avec des cǒnes progradant vers le nord‐est (ces grèzes forment l'essentiel du dépǒt): des grèzes médianes, alternativement brunes et jaunes, correspondant à un dépǒt d'intercone; des grèzes supérieures coïncidant avec un nouveau cone progradant vers l'est. Les grèzes des trois formations sont essentiellement des grèzes maigres ‐ la part des éléments fins excède rarement quelques pour cent ‐ composées surtout d'éléments de la taille des graviers: les éléments de taille supérieure à 2 mm représentent souvent plus de la moitié de l'échantillon. Ceci est directement lié a la nature lithologique des calcaires sublithographiques de l'Oxfordien moyen, qui fournissent fort peu de matériaux fins. Ces grèzes ont été affectées par des processus post‐sédimentaires: cryoturbation, alteration et induration.
Le Rǒle des Coulées de Pierres Sèches dans la Genèse d'un Certain Type d'Éboulis Stratifiés
Authors: Hétu Bernard , van Steijn Henk , Bertran Pascal 
Published: February 2007

AbstractDes expériences de coulées sèches artificielles (grain flow) effectuées dans la carrière de Bélesten (Pyrénées) et les observations réalisées (levés stratigraphiques, analyses sédimentologiques) dans le cǒne stratifié artificiel de la carriére de Remollon (Alpes du Sud), construit au convoyeur et évoluant exclusivement par coulées sèches, ont permis d'élaborer un nouveau modèle de stratogenèse. Dans ce modèle, les lits fins sont constitués de matériel infiltré à la base d'un flux relativement rapide de pierraille openwork en état de dilatation du fait des multiples collisions interparticules (effet de crible). Une fois en place, ces lits fins servent de plan de glissement pour les coulées sèches suivantes qui descendent ainsi de plus en plus bas sur le versant. Les lits grossiers, caractérisés par une texture ouverte, un granoclassement inverse marqué et une forte imbrication des éléments, correspondent aux lobes terminaux des coulées sèches qui viennent peu à peu recouvrir leur plan de glissement suivant un processus de fossilisation remontante. Le modèle des coulées sèches rend compte de manière satisfaisante des principales caractéristiques de l'éboulis stratifié relique de Bélesten, un type d'éboulis qui semble très répandu tant dans les Pyrénées que dans les Alpes. Nécessitant un renouvellement constant des stocks de débris à la těte de I'éboulis, les coulées sèches évoluent dans des roches trés gélives se débitant en menus fragments, mais livrant peu d'éléments fins. La coulée sèche est un processus ubiquiste signalé aussi bien dans les régions chaudes et arides que dans les zones tempérées et périglaciaires. Les éboulis reliques à coulées sèches n'ont done pas de signification paléoclimatique spécifique. Il est clair cependant que dans le contexte des moyennes latitudes, les paysages ouverts et à forte productivité détritique (cryoclastie) des périodes froides du Pléistocène leurs étaient spécialement favorables.
Cryogenic landslides on the Yamal Peninsula, Russia: Preliminary observations
Authors: Leibman Marina O. 
Published: February 2007

AbstractCertain processes occurring in the northern part of the permafrost zone pose hazards for construction. These include cryogenic landslides. Three types are discussed for the Yamal Peninsula: shearing slides (active layer detachment failures), ground ice slumps, and earth flows. The first prevail in size and number.