I was long in doubt on some points concerning the origin of those
taluses. Plainly enough they were derived from the cliffs above them,
because they are of the size of scars on the wall, the rough angular
surface of which contrasts with the rounded, glaciated, unfractured
parts. It was plain, too, that instead of being made up of material
slowly and gradually weathered from the cliffs like ordinary taluses,
almost every one of them had been formed suddenly in a single avalanche,
and had not been increased in size during the last three or four
centuries, for trees three or four hundred years old are growing on
them, some standing at the top close to the wall without a bruise or
broken branch, showing that scarcely a single boulder had ever fallen
among them. Furthermore, all these taluses throughout the Range seemed
by the trees and lichens growing on them to be of the same age. All
the phenomena thus pointed straight to a grand ancient earthquake. But
for years I left the question open, and went on from canyon to canyon,
observing again and again; measuring the heights of taluses throughout
the Range on both flanks, and the variations in the angles of their
surface slopes; studying the way their boulders had been assorted and
related and brought to rest, and their correspondence in size with the
cleavage joints of the cliffs from whence they were derived, cautious
about making up my mind.
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