But Grand As Is This Vision Delineated In These Old Records, This Is
Not All; For There Is Not Wanting Evidence Of A Still Grander
Glaciation Extending Over All The Valleys Now Forming The Sage Plains
As Well As The Mountains.
The basins of the main valleys alternating
with the mountain ranges, and which contained lakes during at least
the closing portion of the Ice Period, were eroded wholly, or in part,
from a general elevated tableland, by immense glaciers that flowed
north and south to the ocean.
The mountains as well as the valleys
present abundant evidence of this grand origin.
The flanks of all the interior ranges are seen to have been heavily
abraded and ground away by the ice acting in a direction parallel with
their axes. This action is most strikingly shown upon projecting
portions where the pressure has been greatest. These are shorn off in
smooth planes and bossy outswelling curves, like the outstanding
portions of canyon walls. Moreover, the extremities of the ranges
taper out like those of dividing ridges which have been ground away by
dividing and confluent glaciers. Furthermore, the horizontal sections
of separate mountains, standing isolated in the great valleys, are
lens-shaped like those of mere rocks that rise in the channels of
ordinary canyon glaciers, and which have been overflowed or
pastflowed, while in many of the smaller valleys roches moutonnees
occur in great abundance.
Again, the mineralogical and physical characters of the two ranges
bounding the sides of many of the valleys indicate that the valleys
were formed simply by the removal of the material between the ranges.
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