734 ARTHUR C. TROWBRIDGE 



of very small valleys. Fans also occur along the mountains outside 

 the mapped area. They were seen northeast of Aberdeen and at 

 Keeler. 



SHAPE AND TOPOGRAPHY 



In general there are two controlling factors in the shapes of the 

 fans. At their mountainward edges they are confined by the walls 

 of the mouths of the canyons, from which they take their form. 

 Their outer edges deploy slightly on the plain. Nos. 2 and 8 extend 

 about a mile into their canyons, and No. 4 extends still farther up 

 Mazourka Canyon. Nos. 1 and 3 show deployment on the plain. 

 No. 2 is made up of two smaller fans, with a depression at their 

 junction. 



The surfaces of these fans are very similar to the surface of the 

 Sierra bajada, except that all features are on a smaller scale, the 

 fans, except No. 2, are simpler and remain separate, and these fans 

 are not now in process of dissection. The individual fans show 

 numerous radiating channels and low ridges similar to those on the 

 Sierra plain, but they give the surface here a relief of no more than 

 7 or 8 ft. at a maximum. The ridges are almost invariably belts 

 of bowlders. The fans are not dissected as is the Sierra bajada. 

 The streams still flow on the surface in the radiating channels, but 

 they flow only after the infrequent rains in the mountains. 



The slope of the fans varies considerably from head to outer 

 edge. Fan No. 8 has a slope of about io° at its head, 5-6 midway 

 of its length east and west, and approaches flatness at its outer 

 edge. Fan No. 1 has a slope of more than 600 ft. per mile in its 

 upper part. The upper part of fan No. 2 slopes westward 800 ft. 

 in a mile. This is steeper than the average. 



MATERIALS 



These fans at the foot of the Inyo Mountains have not been 

 dissected, and exposures of the material are therefore few and shal- 

 low. Some data can be collected from surface materials, there are 

 a few shallow cuts along the channels, and one prospect pit affords 

 a good exposure. 



Each fan is made up of pieces of the kind of rock in which the 

 canyon back of it is cut. For instance, 99 per cent of the material 



