LAKE ESCARPMENT MORAINES. 659 



protrusion into the basin. But instead this morainic system passes the basin 

 with scarcely a mile of southward deflection. It is striking-ly in contrast 

 with the Cleveland, or next earlier morainic belt, which has a loop extending 

 southward 20 to 25 miles into the basin. 



It may be objected that the movement toward the border of the basin 

 was comparatively weak, the main movement being along the axis. This 

 objection is, however, only another way of stating that the ice sheet was too 

 thin in this part of the lake basin to have a strong inovement. It is doubtful 

 if its thickness was half that of the portion in the eastern end of the basin. 



Along its outer border this morainic system usually shows a relief of 

 20 to 40 and occasionally 60 feet; but the country to the south rises rapidly 

 and soon reaches an altitude much above the morainic crest. The relief is 

 best shown where the moraine crosses valleys, such as the Cassadaga, 

 Chautauqua, and Conewango, but it is in many places conspicuous along 

 the face of the escarpment. 



Between the members of this morainic system there are valley-like 

 sags, above which the ridges rise to heights of 20 to 40 feet or more, there 

 being nearly as much relief as on the outer border of the system. The 

 sags aff"ord convenient lines for streams to follow, and the peculiar winding 

 courses and sharp deflections of the creeks on the south border of the Lake 

 Erie Basin in northwestern Pennsylvania and northeastern Ohio are in large 

 part due to the controlling influence of the sags. 



TOPOGRAPHY. 



This morainic system, like the earlier ones, presents considerable 

 variation in topographic expression, ranging from a comj)aratively smooth 

 ridge with only gentle undulations to intricate hummocky tracts inclosing 

 basins that hold ponds and small lakes. Between these types is the 

 well-defined ridge that carries sharp hummocks and has its surface indented 

 with basins. There is also some contrast between different moraines of this 

 system, the Euclid moraine having, on the whole, less strength of expression 

 than the other moraines. In the detailed discussion which follows, the 

 Euclid is first considered, after which the other moraines follow in turn 

 from the outer toward the inner part of the morainic system. 



