314 



EARTH FEATURES AND THEIR MEANING 



hummocks or knobs, so that the surface has often been referred 

 to as " knob and basin " topography (plate 17 C). 



Kames. Within reentrants or recesses of the ice margin the 

 drift deposits were especially heavy, so that high hills of hummocky 

 surface have been built up, which are described as kames. Most 

 of the higher drift hills have this origin. They rarely have any 

 principal extension along a single direction, but are composed in 

 large part of assorted materials. In contrast with other portions 

 of the morainal ridges they lack the prominent basins known as 

 kettles. Other kames are high hills of assorted materials not in 

 ,- -_L... direct association with mo- 



raines and believed to have 

 been built up beneath glacier 

 wells or mills (p. 278). 



Outwash plains. Upon the 

 outer margin of the moraine 

 is generally to be found a plain 

 of glacial " outwash " com- 

 posed of sand or gravel de- 

 posited by the braided streams 

 (Fig. 308, p. 280) flowing from 

 the glacier margin. Such 

 plains, while notably flat (Fig. 

 338), slope gently away from the moraine. Between the outwash 

 plain and the moraine there is sometimes found a pit, or fosse 

 (Fig. 309, p. 281), where a part of the ice front was in part buried 

 in its own outwash (Fig. 339). 



Pitted plains and interlobate moraines. Where glacial outwash 

 is concentrated within a long and narrow reentrant, separating 

 glacial lobes, strips of high plain are sometimes built up which 

 overtop the other glacial deposits of the district. The sand and 

 gravel which compose such plains have a surface which is pitted by 

 numerous deep and more or less circular lakes, so that the term 

 "pitted plain " has been applied to them. The surface of such a 

 plain steadily rises toward its highest point in the angle between 

 the ice lobes. Though consisting almost entirely of assorted 

 materials, and built up largely without the ice margins, such 

 gently sloping pitted platforms are described as interlobate mo- 

 raines. Upon a topographic map the course of such an inter- 



FIG. 339. Fosse between an outwash plain 

 (in the foreground) and the moraine, 

 which rises to the left in the middle dis- 

 tance. Ann Arbor, Michigan. 



