Plate 11.—(b) View Across Part of Crater Lake, Oregon. This great hole, 3,000 to 4,000 feet deep and 6 miles in diameter and now partly filled with a lake 2,000 feet deep, was formed by a subsidence of the top of a once great cone-shaped volcano fully 14,000 feet high above the sea. The high rock in the distance rises 2,000 feet above the lake which is over 6,000 feet above sea level. The island is a small volcano of recent origin. (Photo by Russell, U. S. Geological Survey.)
Plate 12.—(a) Detailed View of Part of the Very Oldest Known (Archeozoic) Rock Formation of the Earth. The rock is distinctly stratified and represents sands and muds deposited layer upon layer upon a sea floor at least 50,000,000 years ago. The sands and muds first consolidated into sandstone and shale below the earth’s surface. Then, under conditions of heat, moisture, and pressure, they were notably altered, mainly by crystallization of minerals, and raised high above sea level. Finally the strata were laid bare by erosion. (Photo by the author.)
Plate 12.—(b) A Twisted Mass of Stratified Archeozoic Limestone Surrounded by Granite in Northern New York. The limestone was enveloped in the granite while it was being forced in molten condition into the earth’s crust. (Photo by the author.)