^^9 



The Ice-currenfs of MitfHcsofa -- I'p/ian/. 



at the outer or eastern Ijelt of tlie terminal moraine as traced in 

 Rice, Steele and Freeborn counties, and onward to central Iowa. 

 The angle formed b}^ the margins of these portions of the ice-sheet, 

 moving respectively from the northeast and the northwest, was at 

 Crystal lake and Buck hill in Burnsville, Dakota county; from 

 which point northwesterly, along an extent of a hundred miles or 

 more, these ice-currents were pushed obliquely against each other. 

 At a late date in this last glacial epoch, after the ice-border 

 had for the most part retreated considerably from its farthestlimit, 

 it is known to have halted in its recession (and it even probabiy 

 re-advanced), forming a second belt of morainic accumulations, 

 usually from five to fifteen miles back or inside from its former 

 line of drift-hills. This second morainic belt is well exhibited 

 from Rice county south to central Iowa, and at the west side of 

 this lobe of the ice-sheet upon the Coteau des Prairies. At this 

 time the ice-sheet that was pushed southwt^stward from lake Su- 

 perior and northern Wisconsin ])robably terminated only a few miles 

 back from its earlier limit east of lake St. Croix, and in Washing- 

 ton, Dakota and Ramsey counties, and in the east edge of Henne- 

 pin county at Minneapolis. But farther northw^ard the presence 

 of bluish till, weathered next to the surface to a yellowish color, 

 containing boulders and pebbles of limestone and of Cretaceous 

 shale and other material brought from the northwest overlying the 

 red till with rock fragments from the region of lake Superior, 

 proves that the ice-current from the northwest was stronger and 

 extended farther, the ice on this side of the great western lobe of 

 the ice-sheet being theiefore even deeper, at least in comparison 

 with the eastern ice flowing southwestward from lake Superior,, 

 than in the former part of this glacial epoch wdien these ice-fields 

 covered their greatest area. In that earlier part of this epoch the 

 ice-currents from the northwest and northeast had met along a line 

 drawn from Crystal lake and lake Mianetonka northwestw^ard, but 

 now, when elsewhere the border of the ice-fields had somewhat 

 retreated and formed the second and inner terminal moraine, the 

 ice flowing from the west extended eastward across Wright and 

 Hennepin, Sherburne aud Anoka counties, to the St. Croix river 

 at the east side of Chisago county, and into the adjoining edge of 

 Wisconsin, pushing back the ice-current that came from lake 

 Superior and covering the red till brought by that ice with the 

 characteristic blue till brought by the ice from the northwest and 

 west. 



