GLACIATION IN THE TELLURIDE QUADRANGLE 72u 
(1) of the areas indicated as landslide near Trout Lake on the areal 
map of the Telluride Folio, and (2) the tongue of the landslide area 
extending to the westward down the east slope of the valley of Lake 
Fork, 4 to 5 miles south of Keystone. As notedin the detailed descrip- 
tions of glaciated valleys, there are numerous striated bowlders in 
the two regions referred to, but there has also been a marked amount 
of slipping and readjustment of material, so that the application of 
the principle laid down above, namely, that the most recent agency 
to produce notable results should take precedence, would require the 
mapping of landslide areas on an areal map practically as shown in 
the folio. The application of the same principle results, however, 
in some reduction of the area referred to as the Silver Mountain 
landslide by Mr. Howe.’ For, as noted in the description of the 
upper part of the valley of Prospect Creek, and of the area west of 
Turkey basin and Alta basin, the topography and materials are in 
both cases characteristic of glacial action rather than of landsliding 
for some distance within the boundary of the landslide area as 
mapped in the folio. It is to be said, however, that the lower limit 
of the glaciated area as shown on the map (see Part I) is drawn 
somewhat arbitrarily, since the characteristics due to glacial action 
as already described, and those due to landsliding, are mingled 
together near the boundary in a manner which makes an accurate 
determination of the share which each had in the movement of 
materials difficult, or sometimes impossible. 
With respect to the time relations involved in the landsliding, 
reference has already been made to observations which prove 
conclusively that some of the movements antedated the epoch of 
the more recent glaciation, as for example the great block of Potosi 
rhyolite two and one-half miles south of east of Trout Lake (Fig. 7). 
The well-cleaned-out cirquelike valley head to the northeast of this 
block, as well as the typical ground moraine topography of the 
glacial drift west of Turkey basin and Alta basin, shows that, at 
these points at least, the amount of landsliding since the recent 
glacial epoch has been insignificant, even though other areas near 
by in each case show evidences-of a considerable amount of move- 
ment since the ice withdrew. 
OD. Ctt., Pe 17. 
