Shasta, as we have already seen, is a fire-mountain created by a
succession of eruptions of ashes and molten lava, which, flowing over
the lips of its several craters, grew outward and upward like the trunk
of a knotty exogenous tree. Then followed a strange contrast. The
glacial winter came on, loading the cooling mountain with ice, which
flowed slowly outward in every direction, radiating from the summit in
the form of one vast conical glacier--a down-crawling mantle of ice upon
a fountain of smoldering fire, crushing and grinding for centuries its
brown, flinty lavas with incessant activity, and thus degrading and
remodeling the entire mountain. When, at length, the glacial period
began to draw near its close, the ice-mantle was gradually melted off
around the bottom, and, in receding and breaking into its present
fragmentary condition, irregular rings and heaps of moraine matter were
stored upon its flanks. The glacial erosion of most of the Shasta lavas
produces detritus, composed of rough, sub-angular boulders of moderate
size and of porous gravel and sand, which yields freely to the
transporting power of running water. Magnificent floods from the ample
fountains of ice and snow working with sublime energy upon this prepared
glacial detritus, sorted it out and carried down immense quantities from
the higher slopes, and reformed it in smooth, delta-like beds around the
base; and it is these flood-beds joined together that now form the main
honey-zone of the old volcano.
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