As to the origin of these valleys, and of Yosemite in particular,
there is still some discussion among scientists. Whitney's old theory
of a great cataclysm and the sinking of a small block of the earth's
crust has been entirely displaced, and geologists are now seeking to
determine if glaciers have been solely responsible for the present
landscape or whether ice and water worked hand in hand. A good summary
of the various theories of geological history, as well as a popular
discussion of all the geological phenomena of the region, is contained
in the "Sketch of Yosemite National Park and an Account of the Origin
of Yosemite and Hetch Hetchy Valleys," by Dr. F. E. Matthes of the
U.S. Geological Survey. This government publication may be obtained in
Yosemite at the office of the Superintendent for ten cents.