Friday, October 1, 2010

Happy Birthday Yosemite!

Today marks the 120th birthday of Yosemite National Park. The geology of this spectacular park and World Heritage Site is characterized by granitic rocks and remnants of older rock. About 10 million years ago, the Sierra Nevada was uplifted and then tilted to form its relatively gentle western slopes and the more dramatic eastern slopes. The uplift increased the steepness of stream and river beds, resulting in the formation of deep, narrow canyons. About 1 million years ago, snow and ice accumulated, forming glaciers at the higher alpine meadows that moved down the river valleys. Ice thickness in Yosemite Valley may have reached 4,000 feet (1,200 m) during the early glacial episode. The downslope movement of the ice masses cut and sculpted the U-shaped valley that attracts so many visitors to its scenic vistas today.

Thank you Galen Clark and John Muir for your work in preserving this nation's great wilderness.

Adapted from Nature & History - United States National Park Service: Yosemite National Park