88 IOWA STUDIES IN NATURAL HISTORY 



in extent. These surfaces have maximum rehef of less than 

 10 feet and are poorly drained. Above them stand con- 

 spicuous monadnocks, and below them are abrupt valleys 

 more than 100 feet in depth. The Lancaster plain is rep- 

 resented in the Galena quadrangle by the divides between 

 Sinsinawa and Galena rivers, used as the site of the Hazel 

 Green Pike road, and the divide between Galena River and 

 Smallpox Creek. The tops of these divides consist of flat 

 surfaces or gentle slopes. They average 900 feet above sea, 

 300 feet above present drainage, and 150 feet below the 

 tops of the mounds which stand conspicuously upon them. 

 In Iowa most of the tops of the divides within eight or ten- 

 miles of the Mississippi River are to be correlated with the 

 Lancaster plain; for instance, the divides between Upper 

 Iowa River and the Minnesota line, between Clear Creek 

 and Village Creek, Village Creek and Paint Creek, Paint 

 Creek and Yellow River, Yellow River and Bloody Run, 

 Bloody Run and Sny Magill Creek, the divides north and 

 south of Yellow River, etc. (Figs. 22 and 26). The plain 



Fig. 22. View of the Lancaster plain and the gorges below it, as seen near Waukon 

 Junction, Iowa. 



is also represented in the vicinity of Dubuque. The Lan- 

 . caster plain in the Minnesota portion of the Driftless Area 



