GLACIAL ACTION 673 



the level of growing timber and at the heads of glaciated valleys. Their 

 resemblance to glacial deposits and their association with glaciated areas 

 naturally suggested some genetic connection with glaciers. But in case 

 of the Veta Peak rock streams glacial action is entirely out of the ques- 

 tion. In the first place, no glaciated valleys are found in Colorado at 

 an altitude of only 9,000 feet. In the second place, even where glacia- 

 tion has occurred in Colorado at altitudes of 10,000 to 11,000 feet^ this 

 has happened only in regions of extensive mountain masses. The eleva- 

 tion of Veta Peak, about 11,600 feet, is quite insufficient to have caused 

 the starting of a glacier, even though the peak were located in close prox- 

 imity to extensive mountains of greater size and extent. Still more is it 

 impossible for glaciers to originate on an isolated peak far away from 

 the high mountain ranges and on the edge of the plains. No glaciated 

 areas occur within 10 or 15 miles of Veta Peak. 



It is evident, therefore, that glacial action is in no way necessary for 

 the production of rock streams of the most pronounced type. That rock 

 streams are so common in the high mountain regions of the San Juan is 

 doubtless due to the erosive agencies of glacial ice which have cut back 

 the heads of the valleys into great steep walled amphitheaters and have 

 thus produced conditions unusually favorable for landslides. It would 

 seem, therefore, that rock streams may occur wherever conditions are 

 such as to produce landslides of great mass and of great velocity. That 

 such must have occurred in many other places is more than likely, but, 

 as suggested by Mr. Howe, in most climates vegetation would quickly 

 cover and obscure all evidences of ancient rock streams. 



Just why Veta Peak should have been so favorable for the production 

 of rock streams of evidently very recent origin is not quite clear. To be 

 sure, the very steep mountain slope to the west of the peak was essential, 

 but other mountain slopes of equal steepness have failed to account for 

 like results. It would seem that a uniform igneous rock like that com- 

 posing the summit of this peak, however readily it might break up under 

 the action of frost, would hardly be likely to be precipitated in huge 

 masses. From observations made by the writer in other parts of Colo- 

 rado, he is convinced that rock streams with marked evidence of stream- 

 like motion are by no means rare phenomena, and there is no reason to 

 suppose that such phenomena are limited by any particular geographic 

 bounds. 



It may be noted, in conclusion, that rock detritus is quite capable of 

 assuming parallel lines of flow without the interposition of either glacial 

 action or of landslides. The writer has very often observed in high 

 mountain regions in the Rockies that rock detritus very often arranges 



