132 



KANSAS UNIVERSITY QUARTERLY 



friable shale will yielil rapid!}- and almost or entirely undermine the 

 limestone mantle above, which in time will break away as it is under- 

 mined, thus allowing the terrace to recede westward. 



This is precisely similar to the conditions obtaining at Niagara 

 Falls and many other noted places. But here in Kansas it covers the 

 whole eastern end of the state. 



Often the limestone will have been fissured back of the terrace as 

 shown in /' and c, so that a valley has been cut between it and the 

 main land, leaving a flat topped mound standing alone. Such mounds 

 are of most frequent occurrence, and often give a picturesqueness to 

 the scenery which cannot be described. The frequency of such 

 geographic names as Mound City, Mound ^'alley, Twin Mounds, 

 Blue Mound, etc.. tells its own storv. 



The walls uf >uch niuuiul^ arc aluayb sleep, sometimes almost 

 precipitous, but their formation is easily understood, and is the same 

 as that just given for the production of river bluffs. Thus, the 

 diameter of the top of mound /', figure i, remains constant for a long 

 period on account of the protecting influence of the rock at the 

 summit. But the basal diameter is rapidly growing shorter, because 

 the shale composing the mound so readily yields. Usually the 

 limestone at the top will break back a few feet before it has been 

 undermined, but rarely before the hillside has become very steep. In 

 many instances a part or all the sides of such mounds will be yielding 

 so rapidly that vegetation cannot get a foothold upon it. But usually 

 there is sufficient soil on top of the mound to support vegetation quite 

 well. One noted mound on the west side of the Verdigris river near 

 Independence, locally called Table Mound, contains nearly 1500 

 acres, the whole of which is utilized for an immense farm. Its 

 summit is a level plane, as its name implies, while its walls are so 

 steep no fencing is required excepting where roadways lead up the 

 incline. The country from La Cygne almost to Fort Scott is partic- 

 ularly noted for isolated mounds and broad table lands; while across 

 to the southwest in Labette and Montgonjery counties the same 

 conditions are repeated. 



