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Superficial deposits
Published in A.C. McLean, C. D. Gribble, Geology for Civil Engineers, 2017
Mechanical weathering leads to a physical disaggregation of the original rock mass into smaller particles. This can be caused by any one of several natural agents. For example, freezing of water within a crack produces an expanded wedge of ice which forces the walls of the crack apart. If the process is repeated by alternate thawing and freezing, fragments from the outer surface of the rock eventually break off to form loose scree. The same mechanical effect may be produced locally in the rock by chemical reactions between certain minerals and water that has penetrated along cracks. The hydration of these minerals produces a local increase in volume, and local pressure causes disintegration of the rock. Similarly, entry of water into the minute void spaces in rocks may allow salts to crystallise there and press against the walls of the void, thus weakening the rock.
Surface Processes
Published in F.G.H. Blyth, M. H. de Freitas, A Geology for Engineers, 2017
F.G.H. Blyth, M. H. de Freitas
In cold climates repeated freezing breaks off flakes and angular fragments from exposed rock surfaces, a process referred to as the operation of the ‘ice-wedge’; it leads to the formation of screes on mountain slopes and produces the serrated appearance of a high mountain sky-line. Water enters rocks by pores, cracks, and fissures; the ice formed on freezing occupies nearly 10 per cent greater volume, and exerts a pressure of about 13.8 × 106 N m−2 if the freezing occurs in a confined space. The freezing is thus like a miniature blasting action and brings about the disintegration of the outer layers of rock. The loosened fragments fall and accumulate as heaps of scree or talus at lower levels, material which may later be consolidated into deposits known as breccia. By the removal of the fragments the surface of the rock is left open to further frost action, and the process continues. Some well-known screes in the English Lake District are those along the eastern side of Wastwater, where the mountain slope falls steeply to the water’s edge. Joints and cleavage planes in rocks assist the action of frost and to some extent control the shape of the fragments produced. Very little material of smaller size than 0.6 mm (the upper limit of the silt grade) is produced by the freezing.
Visualizing Terrain
Published in Terry A. Slocum, Robert B. McMaster, Fritz C. Kessler, Hugh H. Howard, Thematic Cartography and Geovisualization, 2022
Terry A. Slocum, Robert B. McMaster, Fritz C. Kessler, Hugh H. Howard
An application named Scree Painter (https://terraincartography.com/screepainter/) has been developed by Bernhard Jenny and colleagues (2010) that uses various digital inputs to simulate hand-drawn Swiss-style rock drawings. Scree is defined as a mass of rocks or stones that form a slope in a mountainous environment. Rock drawings depict bare rock, devoid of vegetation, that is commonly found in alpine environments. They emphasize how bare rock faces and scree might look from an observer on the ground (such as a rock climber) as opposed to how a landscape might be seen in an orthogonal or “birds-eye” view. When drawn by hand using the Swiss style, rock drawings consist of hachures that vary in width and density, which create a shading effect that also simulates the texture of actual rock faces. Scree is drawn as individual rocks of various sizes and shapes. Scree Painter requires four inputs, the first two being a DEM and a shaded relief image. The third input is a polygon data set that dictates where the scree will be placed. These polygons need to be derived through the investigation of landcover information via image interpretation and on-site visits. The fourth input consists of contours, spot elevations, and other map features upon which scree will not be placed. A most interesting aspect of Scree Painter is how the scree is depicted in digital form. In Scree Painter, the scree is rendered with scanned versions of actual hand-drawn scree stones taken from Swiss-style rock drawings. Figure 23.27 shows a sample map produced in Scree Painter. It includes the scanned scree stones, plus additional information such as contours, spot elevations, and water features.
Machine learning driven landslide susceptibility prediction for the Uttarkashi region of Uttarakhand in India
Published in Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards, 2022
Poonam Kainthura, Neelam Sharma
The overburdened material consists of soil, debris, and in-situ rocks. Soils and waste generally lead to rotational slides, whereas in-situ rocks lead to translational slides. In the present study overburden depth factor varies from 0-1 m to >5 m. In-situ soil and scree with in-situ soil are present at places where erosional activities are not too much in action. Older well-compacted debris and older well-compacted debris with in-situ soil formed through ages due to the deposition along pediment zones. Therefore, younger loose debris is present along the active channels. Scree is present mainly in areas where rock is slate and phyllite. Most of the slides concentrate on this material, and slope wash is also present along some slopes. Landslides happen when the tension along the failure position goes beyond the limit of the shearing resistance of overburden mass. The result can cause changes in various parameters such as (1) the angle of the slope (steep or moderate), (2) physical characteristics of slope forming a mass, and (3) spatial variation in depth if slope forming a mass.
Early Cretaceous glacial environment and paleosurface evolution within the Mount Painter Inlier, northern Flinders Ranges, South Australia
Published in Australian Journal of Earth Sciences, 2020
S. B. Hore, S. M. Hill, N. F. Alley
In the Mt Painter area, we see evidence of an Early Cretaceous glacial environment (including talus/scree/solifluction/glacier rock—at least incipient, probably protalus rampart) genetic concept for the RRB. Many bedding and other sedimentological characteristics and textures, for example, observed in the unit are diagnostic of periglacial sediments and are commonly associated with fluvial sediments where creeks run down the hillside. Perhaps the most compelling observation, in accord with the effects of periglacial processes, is that the RRB drapes around the hillslopes with tillites and kame terraces evident in many locations. The glacial interpretation of the RRB is based strongly around field observations, and indeed, when walking along some of the valleys in the MPI area, especially East Painter Gorge, co-author (NFA) has described the vista as like walking through a fossilised talus-draped landscape within northern British Columbia, Canada.
Geomorphic landscape design integrated with progressive mine restoration in clay quarries of Catalonia
Published in International Journal of Mining, Reclamation and Environment, 2021
José F. Martín Duque, María Tejedor, Cristina Martín Moreno, José M. Nicolau, Miguel A. Sanz Santos, Ramón Sánchez Donoso, José M. Gómez Díaz
At smaller scales are examples of replication of natural landforms at: (i) hard rock quarry faces in the UK since the 1970s [45–48]; and (ii) rock roadcuts in France [49]. These methods simulate time compression by designing and building the ‘natural’ rock cliffs or scree (talus) slopes that would tend to form and evolve with time through rock falls and slides that occur preferentially on weathered or fractured rocks, with the more resistant rocks outcropping as main rock protuberances. Equivalent natural cliffs or rock slopes are used as analogues. For a synthesis of the use of geomorphic landform design methods, soil erosion modelling, and landscape evolution modelling, in mine rehabilitation, see [16].