520 THE GEOLOGY OF MINNESOTA. 



[Topography 



westerly through the northeast edge of Ransom, southwestern Worthing- 

 ton, the northeast half of Dewald, the southwestern part of Summit Lake, 

 the northeast part of township IO3, range 48, and through the middle of 

 Willmont. 



This crest of the Coteau des Prairies is a belt from three to five miles in width, composed 

 of massive swells and smoothly rounded, moderately sloping hills of till, : to 50 and rarely 75 to 

 100 feet above the intervening hollows. Their trends are more frequently from north to south 

 or southeast than in other directions; but this approach to uniformity in trend is seldom very 

 noticeable, and their order of arrangement and the form and connected outlines of this range of 

 highland show much variety of contour. At a distance of several miles it generally presents the 

 usual aspect of any moderately rolling prairie, appearing to be of about uniform hight; and upon 

 nearer approach, and in crossing this belt, it is seen to consist only of broad and smooth undula- 

 tions and swells, mire or less sculptured, especially on the southwest side, by streams. A 

 branch one to two miles in width, extends from this belt northward through the east part of Sum- 

 mit Lake township, including within its area the lake of this name. Here, and northerly into 

 Murray county, this most prominently rolling and highest part of the Coteau des Prairies in this 

 latitude forms the watershed between the basins of the Mississippi and Missouri rivers. Its con- 

 nection with the roughly hilly and knolly outer terminal moraine, traced from central Iowa north- 

 ward to Spirit Lake and thence westerly to Oclieyedan mound, south of this county, and still 

 more prominently exhibited along the crest of the Coteau des Prairies in western Murray county 

 and thence northwesterly to the Head of the Coteau, shows that the border of the ice in the last 

 glacial epoch extended to this belt of massively rolling till ; but though it thus represents the 

 outer moraine of that epoch, it nowhere in Nobles county has such roughly broken knolls, and 

 small, short and steep ridges, as are common along nearly all the rest of this morainic line. 



Fartlier westward, the surface of Nobles county is in swells of till, which trend mostly from 

 north to south, more massive and smoother than those which form the outer terminal moraine, 

 and of about the same elevation; or in nearly level, equally high plateaus of till, as at Rushmore, 

 ten miles west of Worthington. and in the southwest part of Little Hock. Mortheast from the 

 morainic belt, there is a descent of 50 to 75 feet within one or two miles, and thence a smooth, 

 slightly undulating area of till extends with an imperceptibly descending slope northeastward 

 twenty miles to the inner moraine beyond Heron lake and the upper part of the Des Moines river. 

 The valleys cut by the creeks which cross this expanse are only 10 to '20 feet deep, and the lakes, 

 sloughs and lowest depressions are about the same amount below the highest land of their vicinity 

 to which the ascent from the lake-shores is usually in prolonged, gentle slopes. On the Saint 

 Paul & Sioux City railroad the slope of this broad, approximately flat area of eastern Nobles 

 county is about 100 feet in the eight miles between Worthington and Hersey, thus averaging a 

 descent to the northeast of twelve feet per mile. 



In western Murray county the outer or first terminal moraine rises in 

 a conspicuous series of hills, knolls and ridges of till, roughly broken and 

 irregularly grouped, separately of small size and hight, but together form- 

 ing an elevated belt from 50 to 100 feet or more above the smooth area of 

 till on each side. It includes the west edge of township 105. range 42, 

 being here only from one-fourth of a mile to one mile wide; the south two- 

 thirds of Leeds ; the northeast two-thirds of Chanarambie, its most con- 

 spicuous portion in this county being Buffalo ridge, 100 to 150 feet high, 

 trending from southeast to northwest, in sections 21 and 16 of this township; 

 the west half of Cameron; and the southwest corner of Ellsborough. Its 



