722 ALLEN DAVID HOLE 
ROCK STREAMS 
Within the Telluride quadrangle there are in all about 20 of the 
peculiar accumulations of angular rock fragments to which has been 
given the name of rock streams or rock glaciers; the location of the 
most of these is shown on the map (see Part I). The character- 
istics of such areas have been noted by various observers in this 
region, although none were recorded for this quadrangle at the time 
the folio was published. ‘They occur for the most part at an alti- 
tude of 11,000 feet or more above sea-level, in cirques or in the upper 
portion of valleys at about the elevation at which cirques occur, 
usually at the base of precipitous walls of rock. They extend in 
some. cases for as much as a quarter of a mile down the somewhat 
flattened bottom of the cirque, and rise as much as 20 to 30 or even 
4o feet above the bottom of the narrow, valley-like depressions 
which separate them from the slopes of talus at the base of the side 
walls, as in the valley of the stream tributary to Mill Creek heading 
west of Dallas Peak. In other cases the rock stream consists of a 
belt or band of rock fragments lying approximately parallel to a 
steep cliff face, the distance covered being less in a direction per- 
pendicular to the cliff than in the direction parallel to it, as in the 
valley of Canyon Creek east of Gilpin Peak, and in Middle basin, 
a tributary of the valley drained by Marshall Creek. In still other 
cases the rock stream covers an irregular area, but is located at 
about that part of the valley head where snow and ice collected in 
the winter would evidently be likely to be largest in amount, and 
protected in such a way as to be likely to remain longest in the 
spring, as for example the small area at the head of Turkey basin 
(Fig. 9). 
In topography the surface of these areas resembles moraines in 
the following respects: (1) the elevations are usually in the form of 
ridges, sometimes irregular in arrangement, sometimes transverse 
to the direction in which the mass is being moved, and sometimes 
parallel or subparallel to the direction of movement; (2) between 
these ridges are many irregular depressions, corresponding to the 
kettles of typical morainic topography, having dimensions up to 
100 by 25 feet and usually not more than to to 15 feet in depth, 
though one exceptional area in Middle basin has a depression 50 to 
