GEOLOGY 123 



pendicular front though ribbed by canons of steep gradient. 

 The Estancia valley, a structural valley at first, now well 

 filled with alluvial wash from all sides, offers exceptionally 

 well fitted land for agricultural purposes, if the underground 

 water supply is sufficiently near the surface and of such 

 quantity as to warrant the sinking of wells for irrigation 

 purposes. The area which drains into this valley is exten- 

 sive and the stucture of the valley is such as has been stated 

 to make it a promising underground reservoir. The question 

 of pumping the water from an economic and practical stand- 

 point, is one, which as yet, has not been satisfactorily an- 

 swered. The alternative of "dry farming" has been tried 

 but with varying degrees of success. 



"Cabezon" A volcanic plug of the Puerco Valley." 



In the Geological ages of the past the Estancia Valley 

 figured conspicuously as a lake area, its salt lakes of today 

 being remnants of a once much larger one. Old shore lines 

 still exist which mark the different levels at which the waters 

 once stood, concentric series of beaches outline the extent of 

 these lakes at various intervals. The largest one covered 

 the greater part of the valley and was several hundreds feet 

 deep at the time of its maxim an extent: Its old cliffs near 

 Chililli are more than one hundred feet in height. So well 

 preserved are its shore features that one can imagine the 



