Democratic Sentinel, Volume 9, Number 48, Rensselaer, Jasper County, 1 January 1886 — Peculiarities of Yosemite Rock. [ARTICLE]

Peculiarities of Yosemite Rock.

A correspondent in the Overland writes: Already I observe two very distinct kinds of structure in the granite of this region, which, singly or combined, deter mine all the forms about this wonderful valley. These two kinds of structure are the concentric structure, on an almost inconceivably grand scale, and a rude columnar structure, or perpendicular cleavage, also on a grand scale. The disintegration and exfoliation of the granite masses of the concentric structure give rise to the bald, rounded domes; the structure itself is well seen in Sentinel Dome, and especially in the royal arches. The columnar structure, by designation, gives rise to Washington Column, and the sharp peaks, like Sentinel Rock and Cathedral Spires. Both these structures exist in the same granite, though the one or the other may predominate. In all the rocks about Yosemite there is a tendency to cleave perpendicularly. In addition to this, in many there is also a tendency to cleave in concentric layers, giving rise to dome-like forms. Both are well seen combined in the grand mass of Half Dome. The perpendicular face wall of this dome is the result of the perpendicular cleavage. Whatever may be our theory of the formation of Yosemite chasm and the perpendicularity of its cliffs, we must not leave out of view this tendency to perpendicular cleavage. I observe, too, that the granite here is very coarse-grained, and disintegrates into dust with great rapidity.