GLACIATION OF THE UINTA MOUNTAINS 795 
Maximum Maximum 
rae omer AS L Av L 
ovine Karlie | dougie Eaver | bimit during | “Limit during: 
Epoch Epoch Earlier Epoch | Later Epoch 
INorthsslopenecssiccci cise <a. 7,200 7,500 8,165 8,500 
Southysloperaacisdec act sel: 6,600 7,250 7,001 8,112 
The explanation of these striking differences seems to rest funda- 
mentally on the general structural conditions in the range. The fact 
that the crest-line is nearer the north than the south margin of the 
mountains is of extreme importance. As a consequence, the north 
slope canyons are shorter than those on the south slope. They descend 
more quickly to elevations where ablation overcame the onward move- 
ment of the ice. Furthermore, the basins on the north slope are in a 
zone of inclined strata, while the south slope basins are located in the 
midst of essentially horizontal beds. These structural conditions 
account for the greater development of the catchment areas on the 
south slope than on the north slope. The widening of the basins, to be 
discussed more fully later, progressed more rapidly in the region of 
horizontal strata than where the beds are inclined. The larger 
catchment areas and the longer canyons are sufficient to explain the 
more extensive glaciation on the south slope. These factors seem 
to have outweighed in importance the greater protection from the 
rays of the sun on the north slope and the more favorable location 
for the lodgment of wind-blown snows on the north. The angle of 
the sun’s rays must have caused more rapid melting on the south 
side, and the prevailing southwest wind must have carried much 
snow from the southern catchment areas and contributed to the 
northern fields, and yet, with the immense basins and long routes to 
low altitudes, the south slope glaciers far exceeded in magnitude those 
on the north slope. 
GLACIAL EPOCHS 
The chief facts about the extent of the ice during the different 
glacial epochs have been given. On the average, the earlier glaciers 
advanced from five to six miles farther down the canyons than did the 
later. In three basins there appears to have been ice during the 
earlier epoch and not during the later. A comparison of the lower 
