PAPERS ON GEOLOGY AND CHEMISTRY 323 



THE INTERCISION OF PIKE RIVER, NEAR 

 KENOSHA, WISCONSIN 



J. R. Ball, North western University 



J. W. Goldthwait, writing in School Science and 

 Mathematics for February, 1908, uses the term ^'inter- 

 cision" to describe a peculiar drainage modification ef- 

 fected by the waves of Lake Michigan. The term is 

 one not common in physiographic usage. Goldthwait 

 mentions several other instances of the same process 

 and Cleland tells how the waves of the ocean may cut 

 into the valley of a river in the same manner that Gold- 

 thwait has described.^ Goldthwait 's use of the term 

 is referred to in quotation marks by Alden in his recent 

 paper on the Quaternary Geology of Southeastern Wis- 

 consin.- My purpose, however, is not to call attention 

 to the use of a term, but rather to describe the process 

 referred to. Intercision, as the term is used by Gold- 

 thwait, is an instance where a lake shortens the course 

 of a stream by intercepting the stream somewhere be- 

 tween its source and its mouth. The conditions for such 

 interception are rather exceptional and the event is a 

 rare one in drainage changes. 



Pike River finds the lower portion of its course incised 

 in the plain of Glacial Lake Cliicago. It crosses this 

 plain in such manner that for nearly three and one-half 

 miles it flows practically parallel to the shoreline of Lake 

 Michigan. The direction of flow is towards the south. 

 T. C. Chamberlin mentions the course of the stream as 

 indicative of a southerly alongshore drift, that, in a 

 higher stage of the Lake than at present, diverted the 

 stream towards the south.^ 



The remnant of the lacustrine plain in this region is 

 suffering rapid removal by the wave erosion of Lake 

 Michigan. It is this fact, plus the parallel position of 

 the stream in relation to shoreline that furnishes the set- 

 ting for intercision. In respect to the retreat of the 



1 Cleland, H. F., Geology, 1916, p. 214. 



= Alden, W. C, United States Geological Survey Professional Paper 

 No. 106, 1918. p. 340. 



'Chamberlin, T. C, Geology of Wisconsin, Vol. II, 1877, p. 130. 



