258 GEOLOGY OF THE HIGH PLATEAUS. 



As we go southward from the Wasatch Plateau, crossing Salina Cation near 

 its middle, we at once begin to ascend the northern slopes of the third 

 chain. We are among the sedimentaries, which dip gently to the westward ; 

 and descending from the south, a noble valley opens into the middle of 

 Salina Cation, with the edges of the lowest Tertiary beds walling it abruptly 

 on the west and the surface of the Upper Cretaceous rising gradually on 

 the east. This lateral valley is named, locally, Strawberry Valley — a name 

 which recurs with great frequency throughout the mountain regions of the 

 West. As we move upward towards the south the dip of the beds increases, 

 and the very long and gentle inclination of the strata at length becomes 

 wrinkled into a monoclinal of large proportions. We perceive this readily 

 when, at a distance of 4 or 5 miles south of Salina Canon, we climb the 

 western wall of Strawberry Valley, and see directly in front of us to the 

 southward the Tertiary beds covered with immense sheets of old lava, 

 but exposed beneath in a deep ravine. We see them rising monoclinally 

 from the west and smoothing out eastwardly to a sensibly horizontal posi- 

 tion at a high altitude. The underlying sedimentaries are well exposed, 

 for erosion has carved away much of the country to the northward and 

 given admirable sections transverse to the main structure lines and axes. 

 Three days' inspection of these northern flanks will convey a full concep- 

 tion of the general features of the structure, for they are very easily read. 

 Climbing the western wall of Strawberry Valley, we reach a platform 

 about 2 miles wide, from which start the long slopes leading up to higher 

 levels. Immediately in front is the Fish Lake Plateau, full 4,000 feet above 

 us. To the south-southeast is an easy ramp leading up to Summit Valley, 

 an elevated interspace between Fish Lake Plateau and Mount Marvine. 

 As we ascend this grade, we have on the right a deep ravine carved into 

 the general plateau mass, laying bare, in an admirable manner, the sweep- 

 ing curves of the Tertiary beds, overlaid by trachyte, both being bent into 

 typical monoclinal form. The strike of this monoclinal is visible, extending 

 south-southwest nearly 15 miles, giving origin to a slope varying in inclina- 

 tion from 18° to "20°, and with no other ravines than the one just mentioned. 

 It conveys to the eye an impression of singular smoothness — like a vast roof. 

 The slope we are ascending is much more uneven ; and, at an altitude of 



