Yosemite Valley

Yosemite Valley is located within the western slope of the Sierra Nevada range, which was subject to considerable asymmetric uplift in the Neogene and Quaternary. Uplift triggered massive erosion, resulting in the origin of valleys several kilometres deep, but undulating surfaces survived along water divides, creating spectacular landscape contrast. Geologically, Yosemite Valley is carved in granites and granodiorites of Cretaceous age, cut by numerous dikes. Jointing exerts evident control on the shape of many landforms, including the famous domes and blind arches. In the Quaternary, high elevation coupled with the location on the windward side, exposed to moist air masses arriving from the Pacific, allowed for the development of extensive mountain glaciation. An ice cap formed over the plateau, carving cirques, whereas long ice tongues descended into the valleys, transforming them into impressive U-shaped glacial troughs. Different intensity of glacial erosion between the trunk and tributary valleys resulted in the origin of hanging valleys and spectacular waterfalls, among the highest on Earth. Evidence of glaciation also includes ice-polished surfaces, roche-moutonnées, moraines and lake basins. Yosemite Valley remains geomorphologically very active, with rockfalls and rockslides being the most visible processes transforming glacial morphology complemented by bedrock abrasion and gravel-bed river erosion.