38 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE, [bull. 182. 
have slipped en masse. Minor slides were also noted in seA^eral of the 
gulches of the mountains about Telluride. 
The Silverton quadrangle has also been the scene of landslides on 
an unusually grand scale. The principal area of landslides, shown 
on PL IV, embraces the country on both sides of Red Creek from 
the lower end of Ironton Park to the head of Mineral Creek, and 
extends vertically up the adjacent slopes for several hundred feet, or 
in places 1,000 feet. That landslides have occurred in this region 
will be evident to all who carefully examine the topographic detail 
within the areas outlined. This detail is unfortunately too small to 
admit of expression on the scale of the topographic map. Apparently 
the movement has been very superficial in comparison with the great 
slides of the Telluride quadrangle. It has taken place in hundreds 
of separate small blocks, which are now outlined by trenches or sinks 
back of the knolls representing the separate masses. When shadows 
are cast in the right direction the individual knolls of this slide area 
stand out very clearly. PL VI represents a small part of the landslide 
surface in the vicinity of the Guston mine. 
The occurrence of such an area of landslide material is especially 
interesting in this case because of the fact that the Yankee Girl, 
Guston, Robinson, Vanderbilt, Paymaster, and other mines are in the 
heart of the area affected. Since in some cases the ore bodies were 
traced continuously from the surface downward to depths of over 
1,000 feet, it is plain that not all of the surface rock has suffered dis- 
location, but it is a notable fact that at each one of these mines there 
is a mound or hill of much-altered rock which stands up as an out- 
crop in place in the midst of the greatly fractured rock which has 
slipped downward to an unknown extent through the landslide 
action. The contrast between a hill of rock in place and the knolls 
representing landslide blocks surrounding it is very striking in the 
case of the hill above the Paymaster mine. A critical examination 
of the mountain side at this point clearly shows that this hill must 
have been a still more prominent point before the landslide epoch. 
The great multitude of small slide blocks descending from the higher 
slope have almost covered Paymaster Hill and have swept down on 
either side to the level of the main gulch. Whether this landslide 
material may have entirely concealed mounds of altered rock corre- 
sponding to those so prominent at the mines mentioned is an interest- 
ing problem to Avhich Mr. Ransome refers. 
The evidence of landslide action is chiefly that of the topography, 
which is entirely irregular and can not have been produced by ordi- 
nary erosion. The mounds or knolls can not be regarded as roches 
moutonnees because of the completely fractured character of the rocks 
found in them and the fact that many of them are soft tuffs, quite 
incapable of having resisted moving ice to form a scoriated mound. 
It is also notably the case that rocks of entirely different character 
