Origin of Eskers
Diagrams showing the origins of eskers. A) A tunnel under the ice, nearly filled with sand and gravel by the subglacial stream which built up its bed to the level of the outlet. B) The same deposit after the ice melting of the supporting ice walls. Slumping has produced the characteristic steep side slopes.
Amadeus W. Grabau A Textbook of Geology (Boston: D.C. Heath & Co., 1920) 505