THE OVEELAND ROUTE COUNCIL BLUPFS TO OGDEX. 



101 



Just before rcacliing the mouth of the canyon the traveler ma}' see 

 a nearly perpendicular bluff or scarp, a few feet high, at the top of 

 the bank above a gully a few rods southeast of a single-arch concrete 

 bridge. This small bluff, which was made by recent uplift along the 

 side of a great fault that parallels the mountain front, is best seen 



from the higher bench land. 



(Sec PL XXVI, 5.) 



The steep face of the mountain range represents the exposed edges 

 of geologic formations whose continuation west of the fault is now 

 far below the level of the plain. The mouth of the canyon is in very 

 old, greatly distorted rocks (Ai'chean gneiss and schist) which were 

 formed before life began on the globe. Warm springs issue near the 

 bridge below the mouth of the canj^on, and where the trolley road 

 passes over a steel bridge Just inside the canyon a warm spring in the 

 south bank of the river steams forth from the contact between pink 

 quartzite and somber-colored gneiss. The water is salty, contains 

 iron, and has a temperature of about 136° Fahrenheit. Rounding a 

 curve brm2;s into view a waterfall which shoots out from the rocks 



O 



several hundred feet above the track and turns to spray. The water 

 collects on the rocks below and cascade^s into the river. This is an 

 artificial fall, made by a hole in a flume that carries water to a hydro- 

 electric plant. Close to the foot of this fall the bedrock wall of the 

 canyon is plastered by a deposit of thoroughly cemented gravel, a 

 remnant of the material that choked the canyon when Lake Bonne- 

 ville backed up into it.^ 



The canyon at this point is very narrow, and there is barely room 

 for the highway on one side and the trolley-car tracks on the other 

 side of the river (PL XXVII). The mountain walls that rise thou- 

 sands of feet above appear almost insurmountable, and directly ahead 

 they seem to completely block further passage upstream. But a 

 little turn shows a thin notch cut by the river tlu-ough a great mass 

 of quartzite beds standing nearly on edge. Tliis is the same pink 

 formation as that in Observation Peak, and its presence and position 



G. K, Gilbert describes this material 



as follows: 



**The lower part of the canyon through 

 its length, but especially near its mouth, 

 is more or less lined with heavy beds of 

 coarse gravel, thoroughly consolidated by 



In some places 





old rounded bottom met no check until 

 it had passed entirely beyond the mouth 

 of the canyon. There followed a time 

 when the lake filled nearly or quite to its 



meanwhile the 



O^den Kiver continued to bring down the 



highest terrace; and 



saui 



accustomed 



deposited 



a ferruginous cement. 

 this forms the bed as well as the banks of 

 the stream; but at others it is cut through, 

 and the original well-worn rock bottom 

 of the old channel is exposed beneath the 

 gravel by the side of the road. It is evi- 

 dent that when this canyon was originally 

 excavated the G^eat Salt Lake was not 

 far if at all above ita present level; so that 

 the rushinir torrent which wore out this sometimes not. 



checked by the rising 



mi 



lated to a very high level, not yet accu- 



, tired 





rately located, j 



and the stream again cut down 



nel, sometimes reaching it^ old 



