Excerpt from Out of Door Studies in Geography, Vol. 2: The Formation of Mountain Ranges; A Study of the Sierra Nevada Mountains are formed either by material thrown out of the interior of the earth by volcanic action; or through the elevation of the earth's surface by forces within the earth. The peaks and ridges, the canyons and valleys, and the other features which give mountains such a rugged surface, are the work of the tearing-down forces. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.