506 THE GEOLOGY OF MINNESOTA. 



[Moraines. 



prominently rolling, mostly in massive swells, 20 to 40 feet above the depressions, but at many 

 places in small, steep knolls and hillocks of similar hight. The elevation of the range above the 

 general level is from 40 to 75 feet. Its material is till, which here contains more gravel and boul- 

 ders than on its smooth, slightly undulating areas which extend at each side beyond the limits of 

 the county. In Minneota this morainic belt is about three miles wide, reaching from Little Spirit 

 lake and Clear lakes west to the Little Sioux river. It here has many knolls and short ridges 

 which continue into Hunter, and are crossed seven to ten miles west of Jackson by the road to 

 Worthiugton. Farther to the north, the moraine forms a prominently rolling tract, about six 

 miles wide, between the Des Moines and Heron lake, rising in smooth massive swells 50 to 75 

 feet above the general level at the top of the bluffs of the river, and 75 to 100 feet above the lake. 



In the southwest part of Cottonwood county, this belt of notably rolling and hilly drift occu- 

 pies the west half of Great Bend, the north part of Springfield, northeastern South Brook, south- 

 western Amo, and nearly all of Rose Hill. Its width in these townships varies from two to five 

 miles. To the northwest from the offset of the Des Moines river which crosses this formation 

 in Springfield, it lies a few miles northeast of this river and parallel with it, having within the 

 limits of this county and especially in Rose Hill township a prominently rolling contour in smooth 

 swells, 20 to 40 feet above the intervening hollows and frequent lakes. To the south from this 

 offset and the great bend of the Des Moines, the second terminal moraine lies west of this river 

 and approximately parallel with it, their distance apart being from one to ten or twelve miles, 

 along an extent of a hundred and forty miles, through Jackson county and onward in a nearly 

 south-southeast course to Pilot mound and Mineral ridge in northern Boone county near the cen- 

 ter of Iowa. 



The most conspicuous portion and most roughly broken contour of this morainic belt in Cot- 

 tonwood county are in the west part of Great Bend, where a group or range of hills, known as the 

 Blue mounds, begins three miles west of Windom and thence extends three or four miles in a north- 

 west course, with a width varying from a half mile to one and a half miles, lying between the Des 

 Mojnes river on the northeast and Spring lakes on the southwest. These hills are composed of 

 till with frequent boulders, and rise in very irregular slopes to hights 100 to 175 feet above the 

 river and 25 to 75 feet above the general level at their west side. The most elevated of these 

 mounds, in sections 17 and 20, are visible from the southeast part of Murray county, fifteen miles 

 to the west; but from the east they can only be seen within a distance of six or eight miles. 



Medial moraine. Across the Des Moines river, the land ascending from it east of Windom, 

 opposite to the Blue mounds, has similar but less prominent morainic features. It consists of 

 irregular knolls, hillocks, and low ridges of till, with enclosed hollows and lakes, occupying a 

 width of two or three miles, and gradually rising in this distance about 100 feet above the Des 

 Moines river. This tract seems to be part of a medial moraine (so called because formed between 

 opposing ice-currents), connected with the second terminal moraine as a branch from its northeast 

 side, and extending north through the two western ranges of sections in Lakeside and Carson. 

 Its most broken portion is found in sections 17, 8 and 5. Carson, which have many small hillsand 

 ridges 40 to 75 feet high, mostly trending from north to south, composed of till with abundant 

 boulders. Ten miles north from these hills in Carson is the morainic tract through which Mound 

 creek flows in Stately, but the intervening area, across which the quartz jte ridge extends from 

 east to west, is destitute of such knolly drift deposits. 



East of the second moraine, the country extending from it to the Des Moines river in southern 

 Jackson county is till, nearly flat through the central part of Middletown for five or six miles 

 northeast from Spirit lake; moderately undulating in the eastern third of Minneota; and in the 

 west part of Des Moines township massively rolling, in parallel swells that trend nearly from 

 north to south, sloping gently down on their east and west sides to the intervening depressions 

 which are 30 to 50 feet lower, the distance between the tops of these undulations being from a 

 half mile to one or two miles. 



The surface of the part of Jackson county east of the Des Moines river is a smooth, nearly 

 flat, but everywhere more or less undulating sheet of till, sloping eastward ten to twenty feet 

 per mile. Its descent on the line of the Southern Minnesota railroad is 173 feet in eleven and a half 

 miles from the junction of the branch to Jackson, at the top of the eastern bluff of the Des Moines. 



Beyond the knolly and broken ascent east from the Des Moines river in the vicinity of Win- 

 dom, the contour changes to a smooth and nearly flat expanse of till, which thence extends seventy- 



