read the excerpt from "the final assault”.
in the narrow crest of this ridge, the basic rock of the mountain had a thin capping of
snow and ice-ice that reached out over the east face in enormous cornices,
overhanging and treacherous, and only waiting for the careless foot of the
mountaineer to break off and crash 10,000 feet into the kangshung glacier. and
from the cornices the snow dropped steeply to the left to merge with the enormous
rock bluffs which towered 8.000 feet.
based on the excerpt, what is the author's purpose?