UINTA STRUCTURE CONCOMITANT FORMS. 13 



and divide the great block, which is a plateau in general outline, into 

 minor plateaus which are separated by intervening but elevated valleys. 

 This is especially the case where- the streams in their upper courses 

 follow for some distance the strike of the beds before turning to cross 

 the more or less abrupt lines of maximum flexure. Sometimes these 

 streams run in deep gorges; in such cases the plateaus are bounded by 

 canons. 



2. Projecting Ridges. When these consequent streams starting near 

 the axis of upheaval take a somewhat direct course across the strike, 

 the general plateau is cut into a series of sharp, abrupt ridges having a 

 trend at light angles to the strike or general axis of upheaval. Thus the 

 points of the ridges face the plain below and are separated by deep gulches 

 and canons, and the observer on the plain below sees before him what 

 appears to be a line of peaks separated by intervening gulches and valleys, 

 and is apt to misunderstand the topographic character of the great mass 

 which is before him. 



3. Axial Peaks. At some stages in the progress of erosion the channels 

 of consequent drainage inosculate, and about their heads gorges are formed, 

 with towering amphitheaters. In such cases an irregular line of crags 

 and peaks will be found along the axis of upheaval. These I call axial 

 peaks. 



4. Flanking Peaks. Sometimes we find a very hard bed or group of 

 beds underlaid by more friable strata on a flank of the upheaval, which 

 harder beds have been carried away by erosion from those portions of the 

 upheaved mass nearer the axis. In such cases each projecting ridge is 

 crowned with a true peak. I call these flanking peaks. 



5. Interrupted Monoclinal Piidges. On the flanks of these upheavals, 

 but farther from the axis than the flanking peaks, monoclinal ridges are 

 often found sometimes broken by gaps which are the channels of inter- 

 mittent or permanent streams, and these ridges are very irregular and 

 often interrupted. Where the downthrow is by simple flexure, a complete 

 series is formed. Where it is partly by flexing and partly by faulting, 

 some of the monoclinal ridges disappear. Where the faulting is on the 

 side of the zone of maximum flexure nearest to the axis, the ridges of the 



