CHAPTER VII.
HOW LAKE TAHOE WAS FORMED Lindgren, the geologist, affirms that after the Sierra Nevada range was thrust up, high into the heavens, vast and long continued erosion "planed down this range to a surface of comparatively gentle topography." He claims that it must originally have been of great height.

Traces of this eroded range (Cretaceous) "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.