508 W. UPHAM— STAGES OF THE ICE AGE 



tinned and was the principal cause of the lobation of the Wisconsin ice 

 fields, their changing, stronger, and faster currents and their freqnent 

 accumulation of marginal moraines. The edge of the ice was then 

 melted more rapidly, on the average, than in any previous part of the 

 Glacial period, so that it acquired generally a steeper gradient of the 

 frontal slope, due to the predominantly marginal melting and to much 

 snowfall upon the border for a width of many miles. Whenever the 

 increased marginal currents carried the ice forward to its edge at a rate 

 equalling or sometimes exceeding that of its melting there, the mainly 

 receding boundary was held stationary or was even pushed forward 

 during several or many years, permitting the englacial and superglacial 

 drift to be amassed in conspicuous terminal and interlobate series of 

 ridges, knolls, and hills. 



During this moraine-forming stage the southern portion of the ice- 

 sheet from Lake Erie to North Dakota consisted of vast lobes, one of 

 which reached from central and western Minnesota south to central 

 Iowa. This lobe in its early maximum extent ended near Des Moines, 

 and its margin was marked by the Altamont moraine, the first and outer- 

 most in the series of twelve successive marginal moraines of this time 

 which are found in Minnesota. When the second, or Clary, moraine 

 was formed, it terminated on the south at Mineral Ridge, in Boone 

 County, Iowa. At the time of the third, or Antelope, moraine it had 

 farther retreated to Forest City and Pilot Mound. 



The fourth, or Kiester, moraine was formed when the southern 

 extremity of the ice-lobe had retreated across the south line of Minnesota 

 and halted a few miles from it, in Freeborn and Fairbault counties of 

 this State. The fifth, or Elysian, moraine, crossing southern Le Sueur 

 County, marks the next halting place of the ice. At the time of forma- 

 tion of this moraine the south end of the lobe had been melted back 

 180 miles from its farthest extent, and its southwest side, which first 

 rested on the Coteau des Prairies, had retired 30 to 50 miles to the east 

 side of Big Stone Lake and the east part of Yellow Medicine County. 

 In its next recession this ice-lobe was melted away from the whole of 

 Le Sueur County, and its southeast extremity was withdrawn to Waconia, 

 in Carver County, where it again halted, forming its sixth, or Waconia, 

 moraine. The seventh, or Dovre, moraine marks a pause in the retreat 

 when the southeast end of the lobe lay on Kandiyohi County. Probably 

 nearly all of the south half of Minnesota was at that time divested of 

 its ice mantle, but nearly all of the north half was yet ice-covered. The 

 glacial boundary across the State had an approximately east to west 



