ANDERSON — THE BIRDS OF IOWA. I39 



differing in age, and to some extent in origin from the drift of 

 either of the others. 



The Kansan drift covers the greater part of southern, south- 

 central and western Iowa. Its whole surface has been carved 

 and shaped by flowing water and developed into an intricate 

 S3'stem of rounded hills and ridges separated by steep-sided 

 ravines. Every foot of the surface is thoroughly drained. A 

 more level surface is found in the small area covered by the Illi- 

 noian drift in Scott, Muscatine, Louisa, Des Moines, Henry, and 

 Lee counties in southeastern Iowa. 



Embracing Buchanan, Blackhawk, Bremer, Chickasaw, Mitch- 

 ell and a number of other counties in northeastern Iowa, is an 

 area of what is known to geologists as the lowan drift. There 

 has been practically no erosion, the streams flow in narrow, shal- 

 low trenches, and before the settlement of the region there were 

 extensive undrained sloughs. 



The youngest drift area is the Wisconsin drift, covering a tri- 

 angular lobe extending down from Minnesota, the base extending 

 from Worth county to Osceola, the apex at Des Moines. Over 

 the greater part of the Wisconsin plain even the rudiments and 

 beginnings of effective drainage have not yet been established, 

 and marshes and sloughs are abundant. The Wisconsin, more 

 than any of its predecessors, was a moraine-forming ice .sheet. 

 Part of the transported materials was piled up around the mar- 

 gin of the lobe in a bewildering series of disorderly hills or 

 knobs, varying from eighty to one hundred and fifty feet in 

 height. 



"Intimately related to the subject of Wisconsin moraines are 

 the many charming lakes of Iowa. There are no lakes worthy of 

 note in the Kansan, Illinoisan or lowan areas. All of our lakes 

 are of Wisconsin age, and most of them occupy basins in the 

 irregularly- piled morainic ridges. . . . Clear Lake lies in such a 

 basin in the eastern moraine, surrounded by prominent construc- 

 tional hills and knobs. Spirit Lake, the Okobojis, and a number 

 of beautiful but less important sheets of water in the same part of 

 the state, are all located in an extensive morainic belt belonging 

 to the recessional series." 



CLIMATE OF IOWA. 



"Climatology of Iowa." From Annual Report of Iowa Weather 

 and Crop Service. By John R. Sage, Director. (Atlas of Iowa): 



