602 THK GEOLOGY Of MINNESOTA. 



[Outer terminal moraine 



similar slope falls to the southwest. On the Winona & St. Peter (Chicago & Northwestern) rail- 

 road, the traveler going west enters the inner morainic belt of the Coteau at the west edge of 

 Minnesota, a little east of Gary, about 1450 feet above the sea (fig. 48). The line crosses this belt 

 obliquely, occupying about four miles, and ascending some 200 feet; then six miles are moderately 

 rolling, mainly in smooth swells; and the next six miles, lying partly on each side of Altamont, 

 are among the knolls and small hills of the outer moraine, 17-50 to 1950 feet above the sea; suc- 

 ceeded by a smooth, slightly undulating area of till, which rises to the summit of this line near 

 Goodwin, 2000 feet above the sea, extends thence nearly level to Kranzburg, and then descends 

 250 feet by a very gradual slope to Watertown. 



From Canby southwestward the eastern ascent of the Uoteau is first a gradual and smooth 

 slope of till, rising some 250 feet within four miles. Into this the East branch of the Lac qui 

 Parle river, three miles south of Canby, has cut a channel 75 feet deep. Next to the southwest 

 the ascent is among rough drift hills and prominent swells, which cover a belt eight to twelve 

 miles wide, their west boundary being three miles east of lake Hendricks. Southwest from Min- 

 neota, Grandview and Marshall, and onward through Lyon county, the smooth foot-slope of the 

 Coteau is from six to ten miles wide, and ascends 200 feet, or more, before coming to the knolls 

 and hillocks of the inner moraine. The upper part of this smoothly sloping sheet of till is chan- 

 neled to a depth of 100 feet by the Redwood river at Camden and Lynd, and to a depth of 80 feet 

 by the south branch of the Cottonwood river where it is crossed by the railroad near Amiret sta- 

 tion, while the smaller streams all flow in narrow ravines. 



Ihe miter or western terminal moraine, accumulated on the southwest border of a lobe of 

 the last ice-sheet,* forms the summit of the Coteau des Prairies in Lincoln county, rising in a con- 

 spicuous series of drift hills, which continues thence north-northwest as a belt of very knolly and 

 hilly drift from one to five miles wide, to the Head of the Coteau, west of lake Traverse. Through- 

 out this distance its material is till with abundant boulders and pebbles, principally of granite, 

 syenite, gneiss and schists, but also including many of limestone. Its surface is broken by a 

 multitude of mounds, short ridges and hillocks, from 10 to 50 feet above the hollows, which occa- 

 sionally contain sloughs and lakelets. 



In Lincoln county the outer moraine is about two miles wide, and extends by the west ends 

 of lakes Benton and Shaokatan, passing through the middle of Lake Benton township, the south- 

 west corner of Diamond Lake, the center of Drammen, and southwestern Shaokatan. Its hight 

 from its east edge is 100 to 200 feet, and from its west edge 40 to 75 feet. In other words, the 

 surface of the drift-sheet adjoining it through this county, along an extent of twenty miles, aver- 

 ages a hundred feet lower on its east than on its west side. This difference was probably in con- 

 siderable part produced by the ice-sheet of the last glacial epoch, in eroding the earlier drift upon 

 which it lay, the material thus obtained being pushed forward and upward to form the moraine 

 Yet the mass of its terminal deposits at this line is small in comparison with the area, reaching 

 fifty miles to the northeast, that was covered by ice which slowly moved, more or less directly, 

 toward this boundary. The entire mass of morainic drift here accumulated, if spread uniformly 

 over this area, could not exceed a depth of six feet; and if it were all spread on the adjoining belt, 

 five or ten miles wide, to supply the amount that was apparently eroded from that part of the pre- 

 viously existing drift-sheet, it would scarcely raise the surface more than to the uniform slope 

 which was probably its earlier contour. It thus appears that the greater part of the region cov- 

 ered by this ice-lobe contributed very little to its terminal moraine, and that if much material 

 was eroded far within the ice-covered area, nearly all of it was again soon deposited, without be- 

 ing far removed from its previous position; the work of the ice-sheet in its central portion being 

 chiefly to excavate and re-deposit, sculpturing the surface anew, but conveying only a small 

 amount of drift to its border. Near the edge of the ice, however it plowed up and carried away 

 to its termination a great freight, and even dug, as appears in the following pages, forty feet be- 

 low the present surface, its bottom being as low as the beds of lakes Benton, Shaokatan and 

 Hendricks. The drift which is now spread above the beds of these lakes east of the moraine, was 

 apparently contained in the glacial sheet, and deposited at its final melting; but most of it had 

 doubtless been eroded from beneath, or had been brought only a few miles, and it seems very 

 unlikely that as much material was held suspended iu the ice throughout the central portions of 

 its area. 



"Compare p. 406 ; also the ninth annual report. 



