The great crust movement of the Quaternary Period was not the last, by any means, though it was the last of great size. There were many small ones later. Several even have occurred within historic times. On March 26, 1872, a sudden earth movement left an escarpment twenty-five feet high at the foot of the range in Owens Valley. The village of Lone Pine was levelled by the accompanying earthquake. John Muir, who was in the Yosemite Valley at the time, describes in eloquent phrase the accompanying earthquake which was felt there. A small movement, doubtless of similar origin, started the San Francisco fire in 1906.
Conditions created by the great Quaternary tilting deepened the valley from eighteen hundred feet at its lower end to twenty-four hundred feet at its upper end. It established what must have been an unusually interesting and impressive landscape, which suggested the modern aspect, but required completion by the glaciers.
Geologically speaking, the glaciers were recent. There were several ice invasions, produced probably by the same changes in climate which occasioned the advances of the continental ice sheet east of the Rockies. Matthes describes them as similar to the northern glaciers of the Canadian Rockies of to-day. For unknown thousands of years the Valley was filled by a glacier three or four thousand feet thick, and the surrounding country was covered with tributary ice-fields. Only Cloud's Rest, Half Dome, Sentinel Dome, and the crown of El Capitan emerged above this ice. The glacier greatly widened and considerably deepened the valley, turned its slopes into perpendiculars, and changed its side cascades into waterfalls. When it receded it left Yosemite Valley almost completed.
There followed a long period of conditions not unlike those of to-day. Frosts chipped and scaled the granite surfaces, and rains carried away the fragments. The valley bloomed with forests and wild flowers. Then came other glaciers and other intervening periods. The last glacier advanced only to the head of Bridal Veil Meadow. When it melted it left a lake which filled the Valley from wall to wall, three hundred feet deep. Finally the lake filled up with soil, brought down by the streams, and made the floor of the present valley.
The centuries since have been a period of decoration and enrichment. Frost and rain have done their perfect work. The incomparable valley is complete.
III
THE PROPOSED ROOSEVELT NATIONAL PARK
Including the Present Sequoia National Park, West Central California. Area, 1,600 Square Miles