Frost and heat and cold sculpture high mountains to sharp,
tusklike peaks and ragged, serrate crests, where their waste is
readily removed.

The Matterhorn of the Alps is a famous example of a mountain peak
whose carving by the frost and other agents is in active progress.
On its face "scarcely a rock anywhere is firmly attached," and the
fall of loosened stones is incessant. Mountain climbers who have
camped at its base tell how huge rocks from time to time come
leaping down its precipices, followed by trains of dislodged
smaller fragments and rock dust; and how at night one may trace
the course of the bowlders by the sparks which they strike from
the mountain walls. Mount Assiniboine, Canada (Fig. 20), resembles
the Matterhorn in form and has been carved by the same agencies.

"The Needles" of Arizona are examples of sharp mountain peaks in a
warm arid region sculptured chiefly by temperature changes.

Chemical decay, especially when carried on beneath a cover of
waste and vegetation, favors the production of rounded knobs and
dome-shaped mountains.

THE WEATHER CURVE. We have seen that weathering reduces the
angular block quarried by the frost to a rounded bowlder by
chipping off its corners and smoothing away its edges. In much the
same way weathering at last reduces to rounded hills the earth
blocks cut by streams or formed in any other way. High mountains
may at first be sculptured by the weather to savage peaks (Fig.
181), but toward the end of their life history they wear down to
rounded hills (Fig. 182). The weather curve, which may be seen on