72 



PHYSICAL GEOLOGY 



Fig. 48. — Stalactites and stalagmites in Marengo Cave, Indiana. (D. Appleton 



and Company.) 



water evaporates on the floor of the cavern are known as stalagmites 

 (Fig. 48). By the union of the stalactites and stalagmites pillars are 

 formed. 



Caverns are also formed in other ways (pp. 209, 298), but the great 



majority are formed 

 from solution. 



Karst. — Karst is 

 used as a descriptive 

 term for any lime- 

 stone region which 

 has been etched and 

 eroded by water into 

 a rough surface (Fig. 

 49). The name is 

 derived from Karst, 

 on the east side of 



Fig. 49. — Block diagram of a karst (limestone) region, 

 illustrating the effect of solution. Sink holes AAA drain 

 surface and discharge their water through under- 



tin 



ground channels to an open valley. Surface streams are 

 lacking, and the main valley has steep sides. The spring 

 at C may be very large. A fault is also shown at C. 



'Modified after I )e Marronne.) 



the Adriatic, where 



