COTTON WOOD AND JACKSON COUNTIES. 5Q5 



Glacial striae. Moraines.] 



each side slopes down two or three degrees.* The former of these courses of 

 striation is probably that which prevailed till the departure of the ice-sheet, 

 when the great quartzyte ridge and the irregularity of the glacial melting 

 caused a deflection of forty degrees toward the east. The later ice-current 

 was steadily maintained during a considerable time, sufficient for planing 

 off a part of this surface of very hai'd quartzyte, but not touching the ad- 

 joining part, which could only escape by having a thin covering of drift. 



FIG. 35. Fio. 36. FIG. 37. 



IS THE K. E. !i OF IN THE IT. W. % OF I THE 8. W. J^ 

 SEC. 36, GERMASTOWW. SEC. 9, DELTON. OF SEC. 2. AMBOY. 

 SKETCHES OF GLACIAL STRLE ON THE QUARTZYTE IN COTTONWOOD COUNTY. 



The drift spread over Cottonwood and Jackson counties is principally 

 till, in part morainic, being accumulated in knolls and hills, or with a 

 prominently rolling surface in massive, smoothly sloping swells, but fpr 

 the greater part it is only gently undulating in contour. Its thickness on 

 the quartzyte ridge varies from nothing to probably fifty feet or more, and 

 in other portions of these counties it probably varies from one hundred to 

 two hundred feet in depth. The moraines to be described were formed at 

 the west border of the ice-sheet of the last glacial epoch, the first when 

 this ice covered its maximum area, and the second after it had receded 

 considerably from its farthest limits, when its retreat was interrupted by a 

 halt and perhaps even by some re-advance. 



First terminal moraine. The outer or western morainic belt of the Coteau des Prairies ex- 

 tends into the south edge of this state along its course of twenty miles next west of Spirit lake, 

 where the greater part of its width lies in Iowa. From the Little Sioux river at the west side of 

 Minneota, through Sioux Valley and Round Lake townships, to Indian lake in southeastern 

 Nobles county, the part of this formation in Minnesota is characterized by numerous small 

 ridges, hillock?, and swells of till, and is from one and a half to five miles wide, reaching north 

 to Skunk lake, to a half mile beyond Rush lake, to Plum Island and Round lakes, and to the 

 north end of Indian lake. Its greatest extent north in this distance is at the north side of Round 

 lake; but south of this a tract about two miles wide and three miles long to the east from State 

 Line lake, is smooth and only slightly undulating, though enclosed by rolling or knolly morainic 

 areas. 



Second terminal moraine. The inner or eastern of the two terminal moraines upon the Co- 

 teau des Prairies extends from the west side of Spirit lake north through the central range of 

 townships in Jackson county. The width of this belt is from three to six miles. Its surface is 



Compare similar observations in Rock county, reported in chapter xviii. 



