scholarly journals Late Quaternary Rock Glaciers, Mount Kenya, Kenya

1980 ◽  
Vol 25 (93) ◽  
pp. 492-497 ◽  
Author(s):  
W. C. Mahaney
Keyword(s):  
Late Quaternary ◽  
Short Interval ◽  
Morphological Characteristics ◽  
Ice Cores ◽  
Rock Glacier ◽  
Glacier Surface ◽  
Side Rock ◽  
Differential Movement ◽  
Probable Presence ◽  
Rock Glaciers

AbstractRock glaciers in Teleki Valley on Mount Kenya exist above 4 000 m below steep valley walls where they are supplied with debris from avalanche couloirs. These valley-side rock glaciers consist of three or four lobes of rubble bounded by transverse furrows resulting from differential movement. No ice cores were observed in these rubble sheets, but “drunken forest” stands ofSenecio keniodendronindicate the probable presence of interstitial ice resulting either from the metamorphism of snow buried under rockfall and slide-rock debris, or from freezing of water beneath the rock mantle. A geological survey of Mount Kenya in 1976 revealed that rock glaciers are anomalous in the Mount Kenya Afroalpine zone above 3 300 m. Analysis of weathering rinds indicates that several rock-glacier lobes were built up over a short interval of time at or near the end of the last glacial maximum (Würm). Oversteepened fronts on the westernmost lobes may have resulted from re-activation coinciding with the advance of glaciers during late Holocene time (<1 000 B.P.). Soils mantle 20% of the rock-glacier surface and have morphological characteristics comparable with soils forming on moraines of late Würm age in upper Teleki, Hausberg, and Mackinder Valleys.

scholarly journals Late Quaternary Rock Glaciers, Mount Kenya, Kenya

1980 ◽  
Vol 25 (93) ◽  
pp. 492-497 ◽  
Author(s):  
W. C. Mahaney
Keyword(s):  
Late Quaternary ◽  
Short Interval ◽  
Morphological Characteristics ◽  
Ice Cores ◽  
Rock Glacier ◽  
Glacier Surface ◽  
Side Rock ◽  
Differential Movement ◽  
Probable Presence ◽  
Rock Glaciers

AbstractRock glaciers in Teleki Valley on Mount Kenya exist above 4 000 m below steep valley walls where they are supplied with debris from avalanche couloirs. These valley-side rock glaciers consist of three or four lobes of rubble bounded by transverse furrows resulting from differential movement. No ice cores were observed in these rubble sheets, but “drunken forest” stands of Senecio keniodendron indicate the probable presence of interstitial ice resulting either from the metamorphism of snow buried under rockfall and slide-rock debris, or from freezing of water beneath the rock mantle. A geological survey of Mount Kenya in 1976 revealed that rock glaciers are anomalous in the Mount Kenya Afroalpine zone above 3 300 m. Analysis of weathering rinds indicates that several rock-glacier lobes were built up over a short interval of time at or near the end of the last glacial maximum (Würm). Oversteepened fronts on the westernmost lobes may have resulted from re-activation coinciding with the advance of glaciers during late Holocene time (<1 000 B.P.). Soils mantle 20% of the rock-glacier surface and have morphological characteristics comparable with soils forming on moraines of late Würm age in upper Teleki, Hausberg, and Mackinder Valleys.

Rock glaciers : II models and mechanisms

1992 ◽  
Vol 16 (2) ◽  
pp. 127-186 ◽  
Author(s):  
W. Brian Whalley ◽  
H. Elizabeth Martin
Keyword(s):  
Morphological Characteristics ◽  
Sensu Stricto ◽  
Good Evidence ◽  
Conclusive Evidence ◽  
Creep Model ◽  
Rock Glacier ◽  
Side Rock ◽  
Glacier Ice ◽  
Rock Glaciers ◽  
Single Flow

This second part of a review deals with the mechanisms of rock glacier formation and flow. The presence of a copious debris supply is important in all models, although the source of ice necessary for deformation of the debris is in dispute. Evidence for the three main models: permafrost creep, debris-covered glaciers and talus deformation (rockslide), are reviewed. Seismic and resistivity evidence suggests a nonglacial (permafrost) origin where such measurements have been made. There is also good evidence that glacier ice can be seen and its extent determined in other examples. Morphological characteristics are presented; in some cases they seem to be applicable to the permafrost creep model but can also be explained by the debris-covered glacier model. The consequences of both these models are discussed in the light of the appropriate flow law models. Several different ways in which talus deformation have been suggested and these can be applied in some cases. Because of confusion in the designation of 'valley side rock glaciers' these are here termed 'protalus lobes'. The origin of these features is still problematical and may not be the same as for rock glaciers sensu stricto. It is argued that there is still no conclusive evidence for a single flow mechanism for all the features ascribed as rock glacier or protalus lobes.

scholarly journals GEOMATIC METHODS APPLIED TO THE CHANGE STUDY OF THE LA PAÚL ROCK GLACIER, SPANISH PYRENEES

2019 ◽  
Vol XLII-2/W13 ◽  
pp. 1771-1775
Author(s):  
A. Martínez-Fernández ◽  
E. Serrano ◽  
J. J. Sanjosé ◽  
M. Gómez-Lende ◽  
A. Pisabarro ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Satellite System ◽  
Ice Age ◽  
Rock Glacier ◽  
Glacier Surface ◽  
The North ◽  
Spanish Pyrenees ◽  
Gnss Receivers ◽  
Rock Glaciers ◽  
Global Navigation Satellite

<p><strong>Abstract.</strong> Rock glaciers are one of the most important features of the mountain permafrost in the Pyrenees. La Paúl is an active rock glacier located in the north face of the Posets massif in the La Paúl glacier cirque (Spanish Pyrenees). This study presents the preliminary results of the La Paúl rock glacier monitoring works carried out through two geomatic technologies since 2013: Global Navigation Satellite System (GNSS) receivers and Terrestrial Laser Scanning (TLS) devices. Displacements measured on the rock glacier surface have demonstrated both the activity of the rock glacier and the utility of this equipment for the rock glaciers dynamic analysis. The glacier has exhibited the fastest displacements on its west side (over 35&amp;thinsp;cm&amp;thinsp;yr<sup>&amp;minus;1</sup>), affected by the Little Ice Age, and frontal area (over 25&amp;thinsp;cm&amp;thinsp;yr<sup>&amp;minus;1</sup>). As an indicator of permafrost in marginal environments and its peculiar morphology, La Paúl rock glacier encourages a more prolonged study and to the application of more geomatic techniques for its detailed analysis.</p>

Rock Glaciers and Block fields, Review and new data

1976 ◽  
Vol 6 (1) ◽  
pp. 77-97 ◽  
Author(s):  
Sidney E. White
Keyword(s):  
Ice Cores ◽  
Colorado Front Range ◽  
Front Range ◽  
Mass Wasting ◽  
Rock Glacier ◽  
Weathered Rock ◽  
Alpine Regions ◽  
Continental Divide ◽  
Glacier Ice ◽  
Rock Glaciers

Tongue-shaped and lobate rock glaciers are recognized in most alpine regions today. For the tongue-shaped, two situations emerge: those with buried glacier ice (debris-covered glaciers) called ice-cored rock glaciers, and those with interstitial ice known as ice-cemented rock glaciers. Those with ice cores are revealed by depressions between rock glacier and headwall cliff (where a former glacier melted), longitudinal marginal and central meandering furrows, and collapse pits. Ice-cemented rock glaciers ordinarily do not possess these features. As applied to 18 rock glaciers in the Colorado Front Range, 11 of 12 east of the Continental Divide are ice-cored, 6 west of the Divide are ice-cemented. The majority of lobate rock glaciers in the Colorado Front Range are on the south sides of valleys, and, except for talus, are the most voluminous form of mass wasting. All those active and above treeline have characteristics common to all rock glaciers. In addition, they originate from talus, contain interstitial ice, move outward from valley walls at 1–6 cm/yr, and transport more debris as a process of erosion than heretofore realized. Block fields and block slopes, in polar and alpine regions, are thin accumulations of angular to subrounded blocks, on bedrock, weathered rock, or transported debris. They extend along slopes parallel to the contour. Block streams are similar but extend downslope normal to the contour and into valleys. They are made of interlocked blocks without interstitial detritus, but many have finer material deeper inside. The fabric of surface blocks indicates that motion most likely occurred during a periglacial time when interstitial debris, now washed or piped out, permitted movement of the whole deposit.

scholarly journals Geophysical analysis of transverse ridges and internal structure at Lone Peak Rock Glacier, Big Sky, Montana, USA

2014 ◽  
Vol 60 (221) ◽  
pp. 453-462 ◽  
Author(s):  
Caitlyn Florentine ◽  
Mark Skidmore ◽  
Marvin Speece ◽  
Curtis Link ◽  
Colin A. Shaw
Keyword(s):  
Genetic Relationships ◽  
The Body ◽  
Rock Glacier ◽  
Glacier Surface ◽  
Topographic Features ◽  
Digital Elevation ◽  
Rock Glaciers ◽  
Composition Structure ◽  
Elevation Model ◽  
Ground Penetrating

AbstractRock glaciers are periglacial alpine landforms that are found in many locations worldwide. Whereas well-developed models of deformation are established for traditional alpine glaciers, rock glacier deformation is poorly understood. Geophysical data from Lone Peak Rock Glacier (LPRG), southwest Montana, USA, are paired with lidar bare-earth 1 m digital elevation model (DEM) analysis to explore potential genetic relationships between internal composition, structure and regularly spaced arcuate transverse ridges expressed at the rock glacier surface. The internal composition of LPRG is heterogeneous, with frozen debris and clean ice overlain by an unconsolidated talus mantle. Upslope-dipping, clearly distinguished reflectors in the ground-penetrating radar (GPR) longitudinal survey at LPRG correspond to transverse ridges. The spacing and slope of individual features at the surface and in the subsurface were measured and compared and are found to be similar. The structures observed at LPRG and other rock glaciers are similar to structures detected in glaciotectonically altered sediment, ice-cored moraines and other rock glacier settings. This finding suggests that transverse ridges on rock glaciers may be used as geomorphic indicators of internal deformation. This study contributes to the body of research on the application of GPR to rock glaciers, and is the first to directly pair and analyze individual surface topographic features with internal structures.

scholarly journals Disaggregating surface change mechanisms of a rock glacier using terrestrial laser scanning point clouds acquired at different time scales

2020 ◽  
Author(s):  
Veit Ulrich ◽  
Jack G. Williams ◽  
Vivien Zahs ◽  
Katharina Anders ◽  
Stefan Hecht ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Point Clouds ◽  
Rock Glacier ◽  
Glacier Surface ◽  
Terrestrial Lidar ◽  
Surface Change ◽  
Relative Contribution ◽  
Rock Glaciers ◽  
Change Mechanisms ◽  
Glacier Flow

Abstract. Topographic change at a given location usually results from multiple processes operating over different timescales. However, interpretations of surface change are often based upon single values of movement, measured over a specified time period and in a single direction. This work presents a method to help separate surface change mechanisms related to the deformation of an active rock glacier, drawing on terrestrial lidar monitoring at sub-monthly intervals. We derive 3D topographic changes across the Äußeres Hochebenkar rock glacier in the Ötztal Alps. These are presented as the relative contribution of surface change during a three-week period of snow-free conditions (2018) to the annual surface change (2017–2018). They are also separated according to the direction perpendicular to the local rock glacier surface (using point cloud distance computation) and the direction of rock glacier flow, indicated by movement of individual boulders. In a 1500 m2 sample area in the lower tongue section of the rock glacier, the contribution of the three-week period to the annual change perpendicular to the surface is 20 %, as compared to 6 % in the direction of rock glacier flow. This shows that different directions of surface change are dominant at different times of the year. Our results demonstrate the benefit of more frequent lidar monitoring and, critically, the requirement of novel approaches to detecting change, as a step towards interpreting the mechanisms that underlie the surface change of rock glaciers.

scholarly journals Age constraints of rock glaciers in the Southern Alps/New Zealand – Exploring their palaeoclimatic potential

The Holocene ◽  
2018 ◽  
Vol 28 (5) ◽  
pp. 778-790 ◽  
Author(s):  
Stefan Winkler ◽  
Christophe Lambiel
Keyword(s):  
New Zealand ◽  
Southern Alps ◽  
Early Holocene ◽  
Age Dating ◽  
Schmidt Hammer ◽  
Rock Glacier ◽  
Glacier Surface ◽  
The Holocene ◽  
Exposure Age ◽  
Rock Glaciers

Two rock glaciers in the valley head of Irishman Stream in the central Ben Ohau Range, Southern Alps/New Zealand, have been investigated using the electronic Schmidt-hammer (SilverSchmidt). Longitudinal profiles on both features reveal a consistent trend of decreasing R(Rebound)-values and, hence, increasing weathering intensity and surface-exposure age on their numerous transverse surface ridges from rooting zone towards the front. Previously published numerical ages obtained by terrestrial cosmogenic nuclide dating (TCND) allowed the calculation of a local Schmidt-hammer exposure-age dating (SHD) age-calibration curve by serving as the required fixed points. Age estimates for the lowermost rock glacier surface ridges fall within the early Holocene between 12 and 10.5 ka and indicate a fast disappearance of the Late Glacial glacier formerly occupying the valley head, followed by the initiation of rock glacier formation around or shortly after the onset of the Holocene. Although it cannot be judged whether the rock glaciers investigated were active within the entire Holocene or only repeatedly during multiple episodes within, their location and intact morphology exclude any substantial glacial activity at Irishman Stream during the Holocene. This has considerable regional palaeoclimatic implications because it opens for the hypothesis that climatic conditions during early Holocene were possibly comparatively dry and favourable for rock glacier initiation, but less so for glaciers. It would also challenge the view that air temperature is the sole major climate driver of glacier variability in the Southern Alps. More work utilising the palaeoclimatic potential of rock glaciers in the Southern Alps is advised.

Origin, structure and geochemistry of a rock glacier near Don Juan Pond, Wright Valley, Antarctica

2020 ◽  
Vol 32 (4) ◽  
pp. 273-287
Author(s):  
Kelsey Winsor ◽  
Kate M. Swanger ◽  
Esther L. Babcock ◽  
James L. Dickson ◽  
Rachel D. Valletta ◽  
...  
Keyword(s):  
Late Quaternary ◽  
Feedback System ◽  
Dry Valleys ◽  
Don Juan ◽  
Soil Leaching ◽  
X Ray Diffraction ◽  
South Fork ◽  
Rock Glacier ◽  
Rock Glaciers ◽  
Ground Penetrating

AbstractThe South Fork of Wright Valley contains one of the largest rock glaciers in the McMurdo Dry Valleys, Antarctica, stretching 7 km from the eastern boundary of the Labyrinth and terminating at Don Juan Pond (DJP). Here, we use results from ground-penetrating radar (GPR), qualitative field observations, soil leaching analyses and X-ray diffraction analyses to investigate rock glacier development. The absence of significant clean ice in GPR data, paired with observations of talus and interstitial ice influx from the valley walls, support rock glacier formation via talus accumulation. A quartz-dominated subsurface composition and discontinuous, well-developed desert pavements suggest initial rock glacier formation occurred before the late Quaternary. Major ion data from soil leaching analyses show higher salt concentrations in the rock glacier and talus samples that are close to hypersaline DJP. These observations suggest that DJP acts as a local salt source to the rock glacier, as well as the surrounding talus slopes that host water track systems that deliver solutes back into the lake, suggesting a local feedback system. Finally, the lack of lacustrine sedimentation on the rock glacier is inconsistent with the advance of a glacially dammed lake into South Fork during the Last Glacial Maximum.

scholarly journals Overview of rock glacier kinematics research in the Swiss Alps

2010 ◽  
Vol 65 (2) ◽  
pp. 135-145 ◽  
Author(s):  
R. Delaloye ◽  
C. Lambiel ◽  
I. Gärtner-Roer
Keyword(s):  
Creep Rate ◽  
Air Temperature ◽  
Climatic Factors ◽  
Creep Behaviour ◽  
Swiss Alps ◽  
Interannual Variations ◽  
Rock Glacier ◽  
Glacier Surface ◽  
Rock Glaciers ◽  
The Alps

Abstract. The acceleration of rock glacier surface velocities over the two last decades and the destabilization of several landforms show that permafrost creep conditions are changing in the Alps. This article summarizes and presents current understanding of creep behaviour of rock glaciers in the Swiss Alps and emphasises changes that have occurred over the last years and decades. The almost homogeneous interannual behaviour of rock glaciers despite different geometry and activity rates indicates a common dependence on external climatic factors (summer air temperature, seasonal snowcover development) which govern changes observed in rock glacier creep rate. The article highlights ongoing efforts to document interannual variations of rock glacier kinematics for the whole area of the Swiss Alps.

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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