396 GEOLOGICAL EXCURSION T<) THE KOCKY MOUNTAINS. 



Bonneville times the eastern spur was exposed to an energetic attack 



of waves from the north. A deep notch was cut in its side, producing 

 a cliff hundreds of feet in height, and the material excavated was piled 

 as a spit of shingle in the pass, partially closing it. As the train moves 

 up the Jordan valley the Shore terrace and the sea cliff can lie seen 



from a distance, and, as it threads the pass, the gravels of the spit 

 appear near at hand. In the pass are the headworks lor the diversion 

 of the . Jordan water into canals Cor the irrigation of the valley. 



The mountains towering above Utah valley are of wonderful bold- 

 ness and beauty, and their precipitous laces are such as result from no 

 orogenic process save that of faulting. Back of the visible mountain 

 crests are extensive uplands, serving as a gathering ground for the 



streams which here and there break through the main ridge in defiles 



and fertilize the valley. Their waters are finally gathered in Utah lake, 

 from which the Jordan river issues, flowing, like that other Jordan after 

 which it is named, from a lake teeming with life to a sea of death. 



The Bonneville and Provo shore lines are to be seen all about the 

 valley, and the Provo shore line is characterized by numerous delta 

 terraces. The delta of the Provo river has a radius of more than 4 

 miles (7 km.), and crowds the railroad close to the lake. Along the 

 mountain base and across the delta terraces run fault scarps, occa- 

 sionally giving one of the shore lines a sudden change of altitude. 



The two sides of the valley are in striking contrast. The eastern, 

 receiving the drainage of tin 1 lofty Wasatch, enjoys the condition essen- 

 tial to fertility in an arid region, and is dotted with thriving villages: 

 Lehi, American Fork, Battle Creek, Provo, Springville, and Spanish Fork are 

 passed by the train. On the west, the low ridge called ( 'edar mountain 

 induces little precipitation and possesses no permanent stream. Kven 

 springs are lacking, and its slopes, clothed only by a scant growth of 

 low bushes, sustain no human home. 



Due east of Provo the face of the Wasatch is unusually steep, rising 

 in a slope of nearly 35° to Provo peaks, and presenting a remarkable 

 section of Paleozoic rocks over 10,000 feet in thickness, from Cambrian 

 Up to Middle Carboniferous, resting on crystalline schists, of which a 

 small exposure is found at the very base of the slopes. These beds all 

 dip eastward, at first very steeply, but with decreasing angle to the 

 east. 



Hobble creek, which waters the town of Springville, built a broad 

 delta at the level of the Provo shore line. The Spanish fork, as the 

 next stream is called, built a still broader delta at the same level, 

 and the two are continent. The Spanish fork built one also at the 

 Bonneville level with a radius of 1,000 feet (1.2 km.). This was widely 

 trenched during the building of the lower delta, so that the head of the 

 lower lies within a gorge excavated from the Upper. Both deltas are 



