94 



PHYSICAL GEOLOGY 



Fig. 71. — Travertine Falls near Davis, Oklahoma. The travertine which has 

 been deposited to form these dams comes from springs containing large quantities of 

 calcium carbonate in solution. The lime carbonate is deposited as travertine when 

 the carbon dioxide escapes. Forty-four dams occur in this creek within a mile. 

 (Oklahoma Geol. Surv.) 



stream. They vary in diameter from a few inches to ten feet or more 

 and in depth to forty or more feet. The size of a pothole depends 

 upon the velocity and volume of the current and the length of time 

 during which the eddy remains at the same point. By the deepen- 

 ing and coalescing of potholes the channels of streams may be mate- 

 rially deepened, streams sometimes accomplishing their greatest work 

 ol erosion in this way. In the Alps there is scarcely a gorge through- 



