CHARACTERISTICS OF THE NORTH ROCK STREAM 667 



of the valley — a contrast made all the more effective because of the com- 

 plete lack of vegetation on the rock stream itself. Kot even the presence 

 of glacial ice in the Alps extending far down below the snow line and 

 into the forested regions of the lower valleys is more striking in the way 

 of contrast than this tongue of white porphyry fragments running far 

 down into the region of red Carboniferous shales. In fact, the resem- 

 blance to a glacier is most surprising, a resemblance that is heightened 

 by a study of the detailed structure of the rock stream. 



In plate 48, figure 1, is seen a view of this rock stream as taken from 

 the west side of the main valley and at a level some 500 feet above the 

 base of the rock stream. To the left of the notch is Korth Yeta Peak 

 and to the right of the same is South Veta Peak. In plate 48, figure 2, 

 is seen a nearer view of the same rock stream taken from the wooded 

 slope to the north of the stream and opposite a point about 1,200 feet 

 above the lower end of the stream. In each view the source of the mate- 

 rial can be seen on the ridge of the peak. The landslide that developed 

 into a rock stream in the lower portion started at the crest of the ridge. 

 The rock broke away in a practically continuous mass between the notch 

 and h, a distance of perhaps three-quarters of a mile. Beyond h to the 

 right the break continued, but the material derived from the part of the 

 mountain covered by the last two gulches to the right of h, as seen best 

 in figure 2, flowed down farther to the south and formed the south rock 

 stream. 



The north rock stream may be divided into three parts — the north 

 brancli, the south branch, and the main stream below the junction. The 

 north branch has about the same width as the south branchy but is much 

 longer and contains much more material. Below the junction it forms 

 perhaps nine-tenths, certainly three-quarters, of the combined stream. 

 The junction of the two branches is best seen in plate 49, figure 1. In 

 this plate the rock material appears much darker than it should, owing 

 in part to under exposure of the photographic plate and in part to con- 

 trast with the snow. 



CHARACTER OF THE 31 ATE RIALS 



The materials composing the two branches is the same, namely, the 

 whitish colored porphyry composing the summit of the mountain. Al- 

 though the rock stream passes down between banks of red shale and 

 sandstone for a distance of 1,700 feet or more, not one particle of any 

 other kind of rock than porphyry is to be seen. Furthermore, the por- 

 phyry fragments present a very unusual uniformity, in that there ap- 



