8 THE LIFE OF DEVILS LAKE 



change iu drainage channels gave Lake Souris an eastern outlet 

 into Lake Agassiz through the Pembina Elver, and Lake ]\Iinne- 

 waukan, its chief source of supply cut off, began to drop and soon 

 was divided into two parts— Stump Lake and Devils Lake, the 

 later history of both of which has been one of stead}^ recession. 



The Devils Lake region is in the midst of what Simpson (I.e.) 

 has termed the "Drift Prairie Plain". It forms an intermediate 

 area between the old Lake Agassiz floor, which forms what is now 

 known as the Red River Valley, on the east, and the Great Plains 

 Plateau, which sweeps westward thru Montana to the Rocky Moun- 

 tains. 



"The Drift Prairie Plain varies in width from about 200 miles 

 at the north to 100 miles at the south and has a general elevation of 

 from 1,500 to 1,800 feet above sea level. This plain has a gradual 

 but gentle slope eastward from the Coteau du Missouri to the Pem- 

 bina escarpment and Coteau des Prairies and southward from the 

 international boundary line to the South Dakota line. This double 

 slope determines the direction of the drainage, causing the several 

 main streams to take a general southeasterly course. The topography 

 of this plain is that of the young drift type characteristic of 

 all that portion of the prairie plains which lies within the limits of 

 the latest ice invasion, and varies from gently undulating through 

 rolling to hilly, the form being due almost entirely to the original 

 disposition of the unmodified glacial drift upon a nearly level plain. 

 The soft, shaly character of the underlying rocks is such that they 

 do not influence the surface topography to any marked extent, ex- 

 cept where occasional groups of low well-rounded hills or full bodied 

 ridges rise above the plain, and these are so well veneered with drift 

 that only their form reveals their origin. 



More important because more numerous, though less conspicu- 

 ous, are the groups of hills and knobby, irregular ridges which 

 stretch across the prairie in a northwest to southeast direction. At 

 times the ridge effect is pronounced and they lengthen out into long 

 looped curves, and again there seems to be simply a confusion of low 

 rounded hills, both types being so characteristic as to suggest at 

 cnce to the student of physiography their origin in glacial moraines. 

 This prairie is otherwise a gently rolling drift plain cut by a few 

 abnormally deep and well defined valleys such as those of the 

 James, the Sheyenne, and the Maple rivers, trending southward and 

 eastward, marked by many shallow, irregularly winding coulees and 

 dotted by thousands of small lakes and marshy areas, occupying 

 numerous sags and swales, which testify to the undrained condition 

 of llie land.'"* 



*Sinipsou, 1. c. pp. 107-8. 



