THE PRE-POTSDAM PENEPLAIN 29 1 



of the vicinity, he would see a wide variety of massive and 

 schistose igneous rocks alternating with formations of metamor- 

 phic sedimentaries. Wherever the rocks are exposed, their 

 schistosity and bedding are seen to be dipping steeply at various 

 angles, and along the valley bottoms the streams flow over their 

 upturned edges. Hand specimens chipped from ledges show 

 rock crumplings on a minute scale; and the dipping beds of 

 hillsides are the remnants of larsfe rock folds that once roofed 



Fig. 2. — View looking west across the valley of the Little Rib river, showing the 

 even upland of the dissected peneplain. Seven miles northwest of Wausau. 



over broad spaces from a few hundred to a thousand feet across. 

 Everywhere the rocks stand on edge and are folded and crum- 

 pled, and reveal a structure like that seen in the Alps, the 

 Alleghanies, or the Rocky mountains. 



While the rocks of the pre-Cambrian area have typical moun- 

 tain structures, there is nothing in the present land surface to 

 suggest mountain topography. The dipping beds and schists 

 stop abruptly at the even sky-line formed by the crests of the 

 flat-topped hills. There is thus an entire lack of sympathy, a 

 striking unconformity, between the gently sloping summits of 

 this main upland area and the internal structure of the rocks. 

 This indifference of surface form to internal structure could be 



