Geological Papers. 59 



shell animals, and of the lime carbonate and silica of sea weeds 

 and sponges. 



THE THIRD PERIOD OF MOUNTAIN-MAKING. 



At the close of the Ordovician period the earth's crust was 

 again forced to wrinkle as it adapted itself to a shrinking in- 

 terior, and old mountains were rejuvenated and new mountains 

 appeared along their borders or along new lines of weakness. 

 Among the new mountains and ridges formed at this time 

 were the Green and Taconic mountains, and a great anticlinal 

 ridge of especial importance to Kansas. It stretched south 

 and southwest from what are now Put-in-bay islands of Lake 

 Erie, along the western border of Ohio, and through Kentucky, 

 Tennessee, Arkansas and Oklahoma. In Oklahoma the Ar- 

 buckle and Wichita mountains were rejuvenated by this 

 geanticline, and in Missouri this great earth fold reelevated 

 the Ozarks and thus gave a mighty impetus to the develop- 

 ment of Kansas. 



Unknown billions of tons of clay, sand and gravel from the 

 Ozarks and the Oklahoma mountains were poured into the Kan- 

 sas basin, and myriads of ocean plants and animals added their 

 skeletons to this debris from the mountains. At about the 

 close of the six million years of the Silurian and Devonian 

 periods the accumulation of sediment and the continued forc- 

 ing up of the neighboring mountain regions probably brought 

 the southeastern portion of Kansas above the level of the 

 ocean, the first dry land in the history of the state. 



The crust of the earth is never stable, especially in regions 

 of mountain-making, and Kansas had to oscillate up and down 

 many times before she reached her present condition of com- 

 parative stability. After being dry land for some thousands of 

 years, southeastern Kansas sank beneath the level of the sea 

 and received a stratum of limestone mud six or seven hundred 

 feet thick in which were included great quantities of flint de- 

 rived from plants and animals, which secrete silica (the chief 

 mineral of flint) from sea water for their skeletons. Another 

 oscillation and southea.stern Kansas became dry land again, 

 and the thick coating of limestone mud became hardened into 

 rock now known as the Mississippian limestone. This time 

 southeastern Kansas remained dry land so long that the rains 

 wore away more than one-third of this formation. Part of 

 the rain water followed the joints of the limestone deep into 



