312 LAND SCULPTURE 



enclose small lakes or marshes, erratic blocks, and quantities of 

 water-worked and more or less stratified drift are the character- 

 istic features. The confused and irregular, but low relief which 

 marks the outer zone of the ice, is generally succeeded by a plain 

 of sand or gravel, the overwash plain, produced by the debris- 

 laden waters which escaped from the front of the ice. 



Karnes, Eskers, and Drumlins. — These are peculiar forms of 

 glacial accumulations which are found in the peripheral zone. 

 Karnes are hillocks or short ridges of stratified drift, formed by 

 the deposition of materials from subglacial streams as they escape 

 from under the margin of the ice. Eskers or Asar are long, 

 winding ridges of sand and gravel, which may have considerable 

 height and which follow the general direction of the moving ice. 

 Several eskers may join one another, just like a stream and its 

 tributaries. The accepted explanation of these ridges is, that 

 they mark the beds of streams which flowed upon or under the 

 ice, near its edge ; the sand and gravel were laid down in channels 

 or tunnels in the ice and thus were prevented from spreading out 

 into a flat sheet. When the ice retreated, the stream deposits 

 were left standing as ridges. Kames and eskers are common in 

 glaciated regions, and are well displayed in New England and in 

 central New York. The latter are probably forming under the 

 Malaspina glacier now. (See p. 157.) Drumlins are elliptical 

 hills or mounds (sometimes 200 feet high), which are arranged 

 in lines coincident with the direction taken by the moving ice. 

 Drumlins are not at all or only partially stratified, and were formed 

 by the combined action of ice and water or by ice alone near 

 the margin of the ice-sheet. Thousands of them exist in the 

 northern United States, especially in New England, Wisconsin, 

 and Minnesota. 



A glaciated topography is one marked by rounded, flowing out- 

 lines, in contrast to the craggy hills of regions which have never 

 been smoothed by ice. In one way or another, a glacier leaves 

 many depressions and basins in its tract, which, when the ice has 

 retreated, become filled with water and form lakes. A glaciated 

 region is preeminently a region of lakes. 



