132 



GUIDEBOOK OF THE WESTERN UNITED STATES 



■J 



faulted up across the river's course, it kept its place by grinding down 

 its bed. 1 

 whicli the 



rocks made a mountain 



river cut a narrow valley. This 



afterward 



agam 



regained its grade throu 



grind 



that 



blocked its course a stream of molten basaltic lava flowed down the 

 channel and for a loim time all water that came this way was turned 



steam. Wh 



,wm 



; its bed down to grade. It has 

 now sunk a deep, narrow canyon in the black basalt so deep that the 

 road up the river is on a bench 100 to 300 feet above the stream. 



The mountains east of Firth and Monroe, rising 7,000 feet above 

 the sea, or 2,500 feet above the plain, are mostly made of limestone 

 of Carboniferous age or older- They contain also younger rocks, 

 but all the beds are so tilted and broken up that their relations are 



difFicult to determin 



Some of the mountains 

 vvithdi'awn. for hi2:h-orrad 



the 



members of the United 



The^ 

 very 



o 



river. 



this term is meant- the area in which 

 dges, makes a rough surface with v< 



a rough surface with very httle soil. Many 

 of the ridges are cracked open along their axes as a result of internal 

 movement after the surface of the lava had cooled. These cracked 



folds 



The 



and tliin to be cultivated, and is used only for pasturage. Farther 

 downstream the "lavas" recede from the river bank, and irrigation 

 projects^ have made great tracts of desert available for settlement. 



^ Water is diverted from Snake Eiver 

 at the Minidoka dam, 80 miles below 

 Blackfoot, and at the Milner dam, 35 

 miles farther west. Jackson Lake, in 

 Wyoming^ just south of Yellowstone Park, 

 has been made into a great reservoir in 

 which 380,000 acre-feet of water, or 

 enough to cover 380,000 acres to a depth 

 of 1 foot, is now stored by the United 

 States Reclamation Service for use on the 

 Minidoka project. During 1914 work was 

 in progress of raising the dam at the out- 

 let of the lake to such an extent as to make 

 it possible to store . 780,000 acre-feet. 

 The expense of tliis new work is being 

 borne by the North and South Side Twin 

 Falls projects, and the additional water 

 obtained will be used on these projects. 

 The Minidoka project includes 117,090 

 acres and during 1913 81,518 acres was 



actually watered. The principal crops 

 raised here are alfalfa, grain, wheat, 

 oats, barley, potatoes, sugar beets, miscel- 

 laneous hay crops, and fruit — chiefly ap- 

 ples. Stock raising and dairying 

 thriving industries. 



At the Milner dam water is diverted fo^ 

 irrigating lands included in the North and 

 South Side Twin Falls projects. The 



irrigated 



determined 



000 



icres. During 1913 about 150,000 

 acres lying within the South Side tract 

 was watered and in cultivation. The land 

 is used for alfalfa, wheat, oats, pasture 



les, pott 

 raising a 

 >s raised 



Sheep and 



The 



lun 



