"still remain in
a number of flat-topped hills and ridges that rise above the later
tertiary surface. There is reason to believe that this planed-down
mountain range had a symmetrical structure, for somewhat to the east
of the present divide is a well-marked old crest line extending from
the Grizzly Peak Mountains on the north, in Plumas County, at least
as far south as Pyramid Peak, in Eldorado County. At sometime in
the later part of the Cretaceous period the first breaks took place,
changing the structure of the range from symmetrical to monoclinal and
outlining the present form of the Sierra Nevada."

This great disturbance he thinks, "was of a two-fold character,
consisting of the lifting up of a large area including at least a
part of the present Great Basin [Nevada and Utah] and a simultaneous
breaking and settling of the higher portions of the arch. Along the
eastern margin a system of fractures was thus outlined which toward
the close of the Tertiary was to be still further emphasized. The main
break probably extended from a point south of Mono Lake to Antelope
Valley and from Markleeville northward toward Sierra Valley. A large
part of the crust block to the west of this dislocation also sank
down. This sunken area is now indicated by Lake Tahoe and by its
northward continuation, Sierra Valley, separated from each other only
by masses of Tertiary lavas.... It is worthy of note that within the
area of the range no volcanic eruptions accompanied this subsidence."

He continues: "As a consequence of this uplift the erosive power of
the streams was rejuvenated, the Cretaceous surface of gentle outline
was dissected, and the rivers began to cut back behind the old divide,
carrying their heads nearly to the present crest line that separates
the slope of the Sierra from the depression of Lake Tahoe."

These rivers are the great gold bearing streams that caused the mining
excitement of 1849. They all head near the Tahoe region, and include
the Yuba, Feather, American, Mokelumne, Calaveras, Cataract, and
Tuolumne.

Here, then, were two crest lines--the old Cretaceous line of which the
Crystal Range immediately overlooking Desolation Valley on the west,
with Pyramid and Agassiz Peaks as its salient points,--and the new
Tertiary crest line, reaching somewhat irregularly from Honey Lake
in the north to Mono Lake in the south. At the north of Lake Tahoe,
"southwest of Reno, a large andesitic volcano poured forth lavas