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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
Depressions in ice, caused by streams flowing on the tops, or at the sides of glaciers, commonly collect sediments. Subsequently, when the glacial ice melts, irregularly shaped, often steep-sided hills of glacial debris can be left behind. These hills or mounds, called kames, consist of sand, gravel, and till. Kames are highly variable but are, typically, meters to tens of meters in longest dimension. Water flowing on the ground beneath glacial ice, too, can create river channels that collect sediment. After the glacial ice melts, the channel sediment may be left behind as an esker, a ridge that resembles an upside-down stream. Eskers contain stratified drift, mostly gravel and coarse sands, deposited by water that once flowed through tunnels beneath glacial ice.
Origin, Usage and Production of Unbound Granular Materials for Road Construction
Published in A. Gomes Correia, Fernando E.F. Branco, Bearing Capacity of Roads, Railways and Airfields, 2020
G. Bjarnason, H.G. Johansson, S. Davitt
Eskers are well-known deposits built up by sub-glacial meltwater streams. The meltwater streams formed tunnels in the body of the glacier, which ran towards the front of the ice mass and there the stream lost its capacity to carry the material and the tunnels became filled with sediments. Today, one can see these accumulations as long, sinuous ridges in the terrain. Very often they have a coarse grained core covered with layers of silt, sand and gravel. In Denmark, Finland and Sweden, these deposits have always been the most important sources of aggregates (Fig. 4).
Groundwater Targeting Using Remote Sensing
Published in Prasad S. Thenkabail, Remote Sensing Handbook, 2015
Glacial deposits also express themselves in various typical forms. “Eskers” or winding ridges composed of poorly sorted sand and gravel. They are the most distinctive of the various landforms composed of ice-contact deposits. Eskers are the bed load deposits of former streams that occupied subglacial ice tunnels or, less commonly, streams on the ice surface. Most eskers are formed during the stagnant or near-stagnant phase of glaciation.
Dynamics of a retreating ice sheet: a LiDAR study in Värmland, SW Sweden
Published in GFF, 2020
Alastair Goodship, Helena Alexanderson
Eskers are key identifiers of previous ice sheet presence and flow orientation during retreat. They often occur in association with distinct marginal and deglaciation features including hummocks, drainage channels and deltas. Eskers were identified according to widely accepted characteristics of sinuous or broken ridges standing above or distinct within surrounding terrain. Eskers may form subglacially, englacially or supraglacially and form parallel or sub-parallel to dominant ice flow direction. Typically, they are divided by cross-sectional shape into round-crested, sharp-crested, flat-crested and multi-crested morphologies with each representing formation at a different point within the glacial system and specific hydrological conditions (Hebrand & Åmark 1989; Lundqvist 1999; Brennand 2000; Boulton et al. 2009; Perkins et al. 2016).