The forms of rock slopes in the Cape Fold Mountains
The forms of rock slopes developed on the quartzitic sandstones of the folded Cape Supergroup strata are explained with reference to rock mass strength and the characteristics of rock masses. (AJC).
Acid igneous rocks of Stavelot Massif, a case of Pre-Hercynian weathering
Acid intrusive and extrusive rocks of the Stavelot Massif (Belgium) have been analyzed for major-and trace elements. The extrusive rocks have been subjected to pre-or syndiagenetic weathering, during which process biotite was a stable mineral
. The acid rocks are considered to be cogenetic on the basis of their Ti-Zr-Rb ratios.
Alps (The) ; Creep ; Glacier dynamics ; Mountain ; Research technique ; Rock glacier ; Switzerland
In this contribution, an approach to measure mass balance and transport within rock glacier fronts is presented. The technique is applied to Gruben and Suvretta rock glaciers, Swiss Alps. The results confirm a conveyor belt-like advance mechanism
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.
Rock fragments in top soils: significance and processes
Rock fragments in soil: surface dynamics
Climatic variation ; Grain size distribution ; Hydrology ; Land use ; Rock ; Soil ; Soil erosion ; Soil properties ; Spatial variation
This introductory paper reviews various aspects of rock fragments in top soils. Such information is required in particular for predicting the impact of climatic or landuse changes on the response of these soils. Particular attention is paid
to the definition and measurement of rock fragment content in top soils, the density of soils containing rock fragments, the spatial distribution and movement of rock fragments in top soils, the effects of rock fragments on some key hydrological processes, thermal
Special issue : the geomorphic and climatic significance of rock glaciers
Deuterium ; Geochemistry ; Glacier ; Meltwater ; Model ; Oxygen 18 ; Palaeoclimatology ; Rock glacier ; United States of America ; Wyoming
In this paper, the AA. discuss stable isotope and stratigraphic data from an ice core obtained from a rock glacier at Galena Creek, northwestern Wyoming, USA. They have presented new, independent evidence that the Galena Creek rock glacier
is genetically a temperate alpine glacier. These findings show that the Galena Creek rock glacier, and perhaps many other rock glaciers, are essentially debris-covered glaciers. The AA. suggest that rock glaciers represent an untapped archive of old glacier ice
Holocene rockwall retreat and the estimation of rock glacier age, Prins Karls Forland
Arctic Region ; Cold area ; Dating ; Erosion ; Holocene ; Model ; Periglacial features ; Rock glacier ; Sediment transport ; Svalbard
This paper presents a simple analytical model for estimating rock glacier age by coupling the ratio of frontal advance to total rock glacier length and the ratio of debris volume in the rock glacier to present debris flux in the talus cone-rock
glacier transition zone. The model was applied to 2 rock glaciers at Prins Karls Forland, Svalbard. The main goal of the model is to produce a reasonable estimate of rock glacier initiation age and corresponding rockwall retreat rates, based on geometrical
Geomorphogenesis ; Glacial features ; Mountain ; National park ; Periglacial features ; Rock ; Slope ; Slovak Republic ; Structural geomorphology ; Tatra Mountains
Substantial part of the alpine relief of the High Tatra is composed of rock slopes. Geomorphological analysis shows that the development of high rock slopes on crystalline rocks is guided, in principal, by their morphostructural position
Surface sealing as affected by various rock fragment covers in West Africa
Rock fragments in soil: surface dynamics
Africa ; Arid area ; Infiltration ; Model ; Porosity ; Rill wash ; Rock ; Semi-arid area ; Soil ; Soil properties ; West Africa
This paper has two main objectives: to analyse the relations between rock fragment parameters (ground cover, position, size) and sealing for a large range of soils of West Africa which is a region where soils containing rock fragments commonly occur
Rock glaciers in Svalbard. Tentative dating and inferred long-term velocities
Arctic Region ; Cold area ; Dating ; Glacier ; Lichenometry ; Moraine ; Rock glacier ; Slope dynamics ; Spitsbergen ; Svalbard ; Tectonics
A long-term approach based on detailed mapping and lichenometry provides additional information concerning talus-foot rock glaciers overstepping raised beaches in Svalbard. Their regional distribution is primarily controlled by the tectonic pattern
and especially by the network of major thrusting faults. Tentative dating of the start of the rock glaciers movement combined with data on their longitudinal development allowed to infer average long-term rates of rock glacier movement and to compare them
The morphological features and environmental conditions of rock glaciers in Tianshan Mountains
China ; Geochronology ; Glacier ; High mountain ; Moraine ; Mountain ; Periglacial features ; Permafrost ; Photointerpretation ; Rock glacier ; Slope ; Xinjiang
Rock glaciers are developed at permafrost areas of periglacial environment in Tianshan Mountains. Based on field surveying and air-photo interpretation, the paper discusses the shape, characteristics of supply area, formation conditions
and environmental differentiations of rock glaciers at head area of Urmqi River in Kalawuchen Range and the head areas of Touado River and Danangou River in Yilanhabierga Range at Shawan County. Formation conditions and morphological characteristics of rock glaciers
Chemical erosion ; Geochemistry ; Island ; Japan ; Microstructure ; Mineralogy ; Porosity ; Rock ; Rock mechanics ; Volcanic rock ; Weathering
To examine the mechanism of rock-strength reduction due to weathering, temporal changes in microstructure of 4 porous rhyolite were investigated at Kozu-shima Island in the western Pacific. With the results of mineralogical investigations
and laboratory tests of pore structure of the rocks, the AA. conclude that the microstructural changes due to chemical weathering strongly influence the reduction of rock strengths.
Discharge and sediment-load characteristics of the Hilda rock-glacier stream, Canadian Rocky Mountains, Alberta
Water discharge and sediment load characteristics of the Hilda rock-glacier stream are described for portions of the 1985 and 1986 ablation seasons. The hydrological behavior of the Hilda rock-glacier stream suggests that the rock glacier acts
as a buffering factor in basin runoff as compared with a similar glacierized basin. In addition, the rock glacier acts conservatively in sediment release from the basin and promotes denudation by dissolution and material transport as dissolved load.
The distribution of permafrost in rock glaciers of the southern Alps (France)
Results of electrical resistivity surveys performed on ten rock glaciers in the southern Alps, in the summer of 1986. The conclusion that these rock glaciers are essentially inherited forms, testifying the passage of recent cold periods
, is confirmed by the discovery on three sites of rock glaciers with a heterogeneous structure, a thawed central part and an accumulation of ice at the snout. It suggests that the rock glaciers in the southern Alps were formed, for the most part, during
Uncertainties in the radiocarbon dating of organics associated with rock varnish : a plea for caution
C 14 dating ; Dating ; Diagenesis ; Geochemistry ; Methodology ; Organic materials ; Rock ; Weathering
The conclusion of the A. is that the interpretation of radiocarbon ages associated with rock varnish is unclear, and there may be similar problems associated with other rock coatings. To obtain reliable ages in the future, the effort must be based
on a careful characterization of different types of organic matter associated with rock varnish. In addition, the ages of different types of organics must be measured where there are independent age controls, and in blind tests.
A rock glacier/debris-covered glacier system at Galena Creek, Absaroka Mountains, Wyoming
Special issue : the geomorphic and climatic significance of rock glaciers
Geochronology ; Glacier ; Glacier advance ; Moraine ; Palaeoclimatology ; Permafrost ; Rock glacier ; United States of America ; Wyoming
At Galena Creek, the ice/debris system has alternated between rock glacier and debris-covered glacier modes due to changes in the size of the accumulation area. These results have important implications for paleoclimatic studies of the ice
The intent of this work is to : 1) present surface velocities on 15 rock glaciers averaged over 12 years (1983-1995) in the Selwyn Mountains; 2) calculate long-term velocities using rock glacier length and lichen age; 3) compare the velocities
A glacial interpretation for the origin and formation of the Marinet Rock Glacier, Alpes Maritimes, France
Special issue : the geomorphic and climatic significance of rock glaciers
Alpes du Sud ; Alps (The) ; France ; Geophysics ; Glacial features ; Glacial flow ; Glacier ; Model ; Moraine ; Permafrost ; Photogrammetry ; Rock glacier
Rock glaciers of the Southern French Alps, specifically the Marinet Rock Glacier, are commonly thought to have apermafrost origin. However, results from ground surveys, relationships between debris and ice input, lichen dating and historical
Effect of rock hardness and moisture content on tafoni weathering in the granite of Mount Doeg-Sung, Korea
Relationships are investigated between growth processes of granite tafoni and rock properties such as rock hardness and moisture content. Field evidence shows that the rock surface of the inner backwalls and ceiling of tafoni have reduced hardness
and higher moisture content compared to the outer visor of tafoni and to vertical cliff walls with no tafoni. This suggests that tafoni arise in weathered rock where conditions of low strength and high moisture content are both satisfied.