664 H. B. PATTON ROCK STREAMS OF VETA PEAK, COLORADO 



of the cirque. This may be clean or may be covered, by a thin, disordered 

 sheet of bowlders and soil. ... All of the accumulations of the sort just 

 described impress one with a sense of motion, looking as if they had flowed 

 as do viscous masses, and were still advancing from the head walls of the 

 cirques downward. So noticeable was this that in the field they were spoken 

 of as 'rock-glaciers' and upon the map receive the name 'rock streams.' " 



The striking differences between these rock streams and ordinary talus 

 slopes on the one hand and landslides on the other hand were plainly 

 brought out by the above named authors. Although some of the less 

 marked rock streams were not so clearly distinct from talus slopes, the 

 larger ones were considered to be of distinctly glacial origin. At the 

 same time it was recognized that they could not be accounted for by the 

 ordinary action of alpine glaciers. In order to account for the remark- 

 able quantity of coarse material composing them and for the fact that, in 

 their opinion^ the material must have been carried along by glacial ice, 

 it was suggested that, during the period of glacial retreat, after most of 

 the ice in the high glacial cirques had disappeared, and only local glaciers 

 of very small extent remained, landslides occurred at the steep-walled 

 heads of the glacial cirques, and the material thus precipitated upon the 

 diminishing glaciers was carried downward by the slowly moving ice and 

 left eventually in stream or moraine-like masses. 



Subsequent investigation by the same authors has revealed the pres- 

 ence of many more such rock streams in other portions of the San Juan 

 Mountains, and mention of them is made in the Ouray and Needle Moun- 

 tain folios of the U. S. Geological Survey. 



Observations made by the writer in different parts of Colorado, but 

 more especially the discovery of some very beautiful rock streams on 

 Yeta Peak during the summer of 1909, convinced him that such phenom- 

 ena are not as rare as might be supposed from the fact that they have 

 only recently been recognized as a distinct topographic feature. It was 

 also very clear from the conditions surrounding the Veta Peak rock 

 streams that glacial action is by no means necessary for their develop- 

 ment. 



That the above-named authors have had reason to change their former 

 views as to the origin of the San Juan rock streams was made known to 

 the writer while he was engaged in the preparation of this paper by the 

 arrival of the advance copy of Mr. Ernest Howe's paper, "Landslides in 

 the San Juan Mountains, Colorado."^ In this beautifully illustrated 

 and extremely interesting paper there is described at some length the 

 various landslides in the San Juan Mountains and included in these phe- 



» U. S. Geological Survey, Professional Paper No. 67. 



