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Sediments and Sedimentary Rocks
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Not all moraines form at the ends of glaciers. Lateral moraines, like the one labeled in Figure 8.33 and the moraine shown in Figure 8.34, are deposited along the sides of mountain glaciers where melting ice leaves debris behind. The ice melted long ago and disappeared from the glacial valley shown in Figure 8.34, but the lateral moraine is testimony to the former presence of an alpine glacier. Medial moraines, found in the centers of glacial valleys, typically form when two glaciers merge, creating trains of till in the center of what is, or was, glacial ice. Medial moraines contain material that was formerly part of lateral moraines belonging to each of the joining glaciers.
The Water Cycle
Published in Aurèle Parriaux, Geology, 2018
The profile along a glacial valley does not resemble that of a valley of a mountain stream or river. The bottom has a series of thresholds (a convex profile) where rocks are hard and over-deepenings, also called ombilics (a concave profile) that occur where rocks are soft. As a solid material, ice can move over these thresholds due to the pressure from the upstream mass of glacier. When a valley glacier melts, it leaves in front of it large lakes that are the over-deepened segments upstream of the obstacle. This phenomenon creates the majority of mountain and piedmont lakes.
The Water Cycle
Published in Aurèle Parriaux, Geology, 2018
The profile along a glacial valley does not resemble that of a valley of a mountain stream or river. The bottom has a series of thresholds (a convex profile) where rocks are hard and over-deepenings, also called ombilics (a concave profile) that occur where rocks are soft. As a solid material, ice can move over these thresholds due to the pressure from the upstream mass of glacier. When a valley glacier melts, it leaves in front of it large lakes that are the over-deepened segments upstream of the obstacle. This phenomenon creates the majority of mountain and piedmont lakes.
Re-visiting the structural and glacial history of the Shackleton Glacier region of the Transantarctic Mountains, Antarctica
Published in New Zealand Journal of Geology and Geophysics, 2022
The type section of the Bennett Platform Formation lies along the flanks of the Shackleton Glacier, suggesting a protracted time interval followed deposition of the Shackleton Glacier Formation. During this interval a landscape with incised glacial valleys, not too dissimilar to today’s topography, was developed (Hambrey et al. 2003). Old glacial deposits, first reported and illustrated by McGregor (1965), are perched high on the south-facing valley wall of the Shackleton Glacier at Dismal Buttress (Figure 6). The deposits, sitting about 200 m above Shackleton Glacier and plastered on a steep slope of Fremouw strata, comprise weakly bedded diamictite, containing dolerite and sandstone clasts, overlain by unstratified till (McGregor 1965, Figures 3 and 4). These Sirius strata represent glacial sedimentation on essentially modern topography but at an early stage in the carving of the glacial valley. From the perspective of the topographic setting and the presence of dolerite clasts, the strata should be assigned to the Bennett Platform Formation. However, it seems improbable that they were contemporaneous either with the type section of the Bennett Platform Formation, which is located about 25 km to the north and up to about 100 m above ice level, or with the Bennett Platform Formation beds documented by Hambrey et al. (2003) at a higher elevation overlying dolerite on the northern flank of Dismal Buttress.
The tectonic history of Adelaide’s scarp-forming faults
Published in Australian Journal of Earth Sciences, 2019
A major glacial valley extends in a northwesterly direction through the present-day Inman Valley. This glacial scour was cut right across the present Kangarilla and Kuitpo blocks on Fleurieu Peninsula and, together with observed ice-movement indicators, implies a northwesterly gradient. In an attempt to reconstruct approximately the glacial geomorphology, the elevations of the points of intersection of the mapped lateral edges of the valley fills with the present land surface were contoured at 50 m intervals (Figure 6). While this is not an exact representation, it does demonstrate the high-relief Carboniferous–Permian topography and shows how the present topography is one of partial exhumation of the glacial valleys. Similar deep glacially scoured valleys have been identified on seismic sections in the Arckaringa Basin by S. A. Menpes in Menpes, Korsch, and Carr (2010). The contours also show the varying elevations of the glacial valley floors. For example, glacial sediments overlying glaciated bedrock are exposed near present sea-level at the coast of Encounter Bay, e.g. at Port Elliot. The dolomite-cemented sandstone exposed on the beach at Chiton Rocks just east of Victor Harbor is likely to be part of the Permian fluvio-glacial succession, implying that the base of the valley fill here lies below sea-level.
Seasonal contributions of water and pollutants to Lake St. Charles, a drinking water reservoir
Published in Canadian Water Resources Journal / Revue canadienne des ressources hydriques, 2020
Biljana Narancic, Isabelle Laurion, Brent B. Wolfe, Sonja Behmel, Alain N. Rousseau
LSC is located on the Canadian Shield in an ancient glacial valley surrounded by steep hills with altitudes varying between 150 and 450 m (the highest peak is at 750 m; Tremblay et al. 2002). Surface deposits are thin with outcrops (APEL 1981). Upstream surface water has naturally low ionic charge, and thus, low conductivity and pH (78.6 μS/cm and 6.7 pH). Approximately, 70% of the lake watershed is covered by dense forests, dominated by deciduous and mixed wood stands. Significant macrophyte growth occurs in shallow areas along the lake shores. Since 2012, macrophyte growth has been extensive and tends to cover 55% of the southern basin area and 36% of the northern basin area (APEL 2014b).