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THE EARTH'S CRUST 



Old Plateaus. If a plateau remains elevated for a 

 great length of time, the rivers are able to widen their valleys 

 and wear away all the interstream spaces, except where 

 these are very broad. Thus the rivers bring the whole 

 surface down to a comparatively low level, with here and 

 there a remnant which has not been worn away, but which 

 shows in its steep sides the edges of the rock layers which 



AN INDIAN HOGAN 



formerly spread over the whole region. If these residual 

 masses are large, they are called by the Spanish name 

 mesas, meaning tables, and if small, buttes, from the French 

 word which means landmarks. 



Some of these mesas are so high and so steep that it is 

 impossible to climb them, and others are simply low, flat- 

 topped hills. A traveler in New Mexico and Arizona 

 will see many of these mesas, which, like the lonely Indian 



