Mount Shasta surpassed even its present sublime height.

Then followed a strange contrast. The glacial winter came on. The sky
that so often had been darkened with storms of cinders and ashes
and lighted by the glare of volcanic fires was filled with crystal
snow-flowers, which, loading the cooling mountain, gave birth to
glaciers that, uniting edge to edge, at length formed one grand conical
glacier--a down-crawling mantle of ice upon a fountain of smouldering
fire, crushing and grinding its brown, flinty lavas, and thus degrading
and remodeling the entire mountain from summit to base. How much
denudation and degradation has been effected we have no means of
determining, the porous, crumbling rocks being ill adapted for the
reception and preservation of glacial inscriptions.

The summit is now a mass of ruins, and all the finer striations have
been effaced from the flanks by post-glacial weathering, while the
irregularity of its lavas as regards susceptibility to erosion, and the
disturbance caused by inter- and post-glacial eruptions, have obscured
or obliterated those heavier characters of the glacial record found
so clearly inscribed upon the granite pages of the high Sierra between
latitude 36 degrees 30 minutes and 39 degrees. This much, however, is
plain: that the summit of the mountain was considerably lowered, and the
sides were deeply grooved and fluted while it was a center of dispersal
for the glaciers of the circumjacent region. And when at length
the glacial period began to draw near its close, the ice mantle was
gradually melted off around the base of the mountain, and in receding
and breaking up into its present fragmentary condition the irregular
heaps and rings of moraine matter were stored upon its flanks on which
the forests are growing. The glacial erosion of most of the Shasta lavas
gives rise to detritus composed of rough subangular boulders of moderate
size and porous gravel and sand, which yields freely to the transporting
power of running water. Several centuries ago immense quantities of this
lighter material were washed down from the higher slopes by a flood of
extraordinary magnitude, caused probably by the sudden melting of
the ice and snow during an eruption, giving rise to the deposition
of conspicuous delta-like beds around the base. And it is upon these
flood-beds of moraine soil, thus suddenly and simultaneously laid down
and joined edge to edge, that the flowery chaparral is growing.