Any steep slope or cliff is especially vulnerable to nature’s methods of
destruction. In the Tetons we see the never-ending struggle between two
conflicting factors. The first is the extreme toughness of the rocks and
their consequent resistance to erosion. The second is the presence of
efficient transporting agencies that move out and away from the
mountains all rock debris that might otherwise bury the lower slopes.
The rocks making up most of the Teton Range are among the hardest,
toughest, and least porous known. Therefore, they resist mechanical
disintegration by temperature changes, ice, and water. They consist
predominantly of minerals that are subject to very little chemical decay
in the cold climate of the Tetons.
Absence of weak layers prevents breaking of the tough rock masses under
their own weight. All these conditions, then, are favorable for
preservation of steep walls and high rock pinnacles. Nevertheless, they
do break down. Great piles of broken rock _(talus)_ that festoon the
slopes of all the higher peaks bear witness to the unrelenting assault
by the process of erosion upon the mountain citadels (figs. 4 and 31).