The Kaneville Esker is the largest esker in Illinois, and is characterized as a long, narrow, steeply sided ridge of glacial sediments, formed during the filling of a former subglacial tunnel. Esker typically form as melt water at the base of the glacier collected into single to complex networks of braided channels or conduits which were cut into the basal ice. Conduits called "Rothlisberger or R-channels" are ice-walled tunnels which transport melt-water to the glacier margin. Melt water being transported through the R-channels can also carry a sediment load which fills these channels creating an esker after the glacier has retreated. Eskers can be found in a variety of shapes and sizes. Some can wind back and forth for tens of kilometers, interconnecting with other eskers, while other can be relatively discontinuous resembling kames. Eskers have also been identified which run over topographic highs. Higher pressure within a water filled tunnel can behave much differently than an open channel or fluvial system, which constantly run down gradient. Pressure within an enclosed tunnel can force water and sediment through conduits which may run up-gradient.
The composition of esker deposits can range from silt to boulders, but are generally composed of sand and gravel materials. Sediments within an esker can exhibit graded horizontal and cross-bedded sequences which record episodes of discharge and sediment deposition similar to open fluvial environments. The sediments which form the esker can be commercially valuable. The deposits are excavated, processed and sold for a number of commercial uses.
Click here for an activity
that can be used in a classroom setting to help students understsand the
processes which form a kame and how to identify them.