Yosemite National Park

Yosemite lands were first preserved by the United States Congress and President Abraham Lincoln who, in 1864, at the height of the American Civil War, granted them to the people of California for preservation. At that time, the federal government was very limited in size and wealth, and the concept of a "national park" had not yet emerged, so authorizing California to preserve these federal lands seemed appropriate. This original land grant comprised just under 39,000 acres (15,500 hectares), or about 60 square miles, and included Yosemite Valley and the Mariposa Grove of giant sequoias. In 1890, Yosemite was added to the new national park system that had begun with the preservation of Yellowstone National Park in 1872.

The park's 200 miles (320km) of roads give access to many of its features by private vehicle and in some areas by free shuttle bus. To get to know the real Yosemite, however, leave your car or shuttle bus and travel even a short distance on a trail. You don't have to go far to discover the grandeur that can be found here and the values this special place offers. Millions of people have come to Yosemite and left refreshed and relaxed and perhaps a bit more knowledgeable about what they want out of life.

Yosemite Valley is at the center of most visitor activity in Yosemite National Park. The Merced River flows across the Valley's flat floor at an elevation (altitude) of 4,000 feet (1220m) above sea level. The Valley floor includes oak and mixed-conifer woodlands and numerous meadows, inhabited by diverse wildlife. The Valley is surrounded by steep, almost vertical, granite cliffs, including the El Capitan monolith, Glacier Point, and Half Dome. Major waterfalls tumble into the Valley, the most prominent of which are Yosemite, Bridalveil, and, less easily seen from below, Vernal, Nevada, and Illilouette. The falls reach their maximum flow in late spring and drop significantly in flow as the season progresses.

The exposed geology of the Yosemite area includes primarily granitic rocks with some older metamorphic rock. The first rocks were laid down in Precambrian times, when the area around Yosemite National Park was on the edge of a very young North American continent. The sediment that formed the area first settled in the waters of a shallow sea, and compressive forces from a subduction zone in the mid-Paleozoic fused the seabed rocks and sediments, appending them to the continent. Heat generated from the subduction created island arcs of volcanoes that were also thrust into the area of the park. In time, the igneous and sedimentary rocks of the area were later heavily metamorphosed.

Yosemite National Park photo gallery

Most of the rock now exposed in the park is granitic, having been formed 210 to 80 million years ago as igneous diapirs 6 miles (10 km) below the surface. Over time, most of the overlying rock was uplifted along with the rest of the Sierra Nevadas and was removed from the area by erosion. This exposed the granitic rock to much lower pressure, and it was also subjected to erosion in the forms of exfoliation and mass wasting.

Starting about 3 million years ago a series of glaciations further modified the area by accelerating the erosion. During that time large glaciers periodically filled the valleys and canyons. Landslides and river erosion have been the primary erosive forces since the end of the last ice age, which ended in this area around 8000 BC.

The total 2425-foot distance from the top of the upper falls to the base of the lower falls qualifies Yosemite Falls as the 6th highest waterfall in the world (with the recent discovery of Gocta Cataracts it presently appears on some lists as the seventh). Although often referred to as a "two-stage drop", the falls actually consist of three sections.