NOTES ON THE PHYSIOGRAPHY OF NORTH DAKOTA 



AND THE CONDITIONS IN CERTAIN 



OF ITS WATERS 



R. T. YOUNG 



Professor of Zoology, University of North Dakota, 

 Director of Biological Station, Devils Lake, North Dakota 



The following notes on the physiography of North Dakota 

 and the conditions in certain of its waters are intended as an 

 introduction to the paper by Dr. Moore and Dr. Carter on the 

 plankton algae of these waters. 



North Dakota may be divided into three main areas: (1) the 

 Red River Valley, occupying the basin of glacial Lake Agassiz ; 

 (2) the drift prairie plain, a region covered with glacial till and 

 boulders and of irregular surface, which slopes gradually upward 

 from the valley to (3) the Missouri Plateau, an elevated table- 

 land occupying the southwestern half of the state. The latter 

 area is deeply cut by the valley of the Missouri River, a little 

 to the east of which, and running nearly parallel with it, is aD 

 irregular line of low hills, constituting the Altamont Moraine, 

 which marks the southwestern edge of the glacier which in the 

 last glacial epoch covered the eastern half of the state, and 

 whose drainage, in its retreat, formed Lakes Agassiz, Souris, and 

 Saskatchewan. Southwest of the Missouri River is the greatly 

 eroded region known as the ' 'badlands," which constitutes the 

 most picturesque feature of the state. 



In the northern part of the area, on the Canadian boundary, 

 is a group of low, irregular hills constituting the Turtle Moun- 

 tains. These hills rise from 120 to 180 meters above the sur- 

 rounding plain, and represent a portion of the Missouri Plateau, 

 isolated therefrom by erosion, prior to the advent of the gla- 

 ciers, and covered by the latter with till to a depth of from 30 to 

 60 meters. Among these hills are numerous spring-fed, fresh- 

 water lakes, the largest of which, just east of Bottineau, has an 

 area of about 6 square kilometers. 



Ann. Mo. Bot. Gahd.. Vol. 10. 1923 



(385) 



