Wikipedia:Today's featured article/August 8, 2005

From Wikipedia, the free encyclopedia

The exposed geology of the Death Valley area records many events associated with plate tectonics. The oldest rocks in the area that now comprise Death Valley National Park and environs are extensively metamorphosed by intense heat and pressure and are at least 1700 million years old. Rifting of the supercontinent Rodinia some 700 to 800 million years ago (mya) allowed sea water to invade until the continental crust broke, giving birth to the Pacific Ocean. The region's first known fossils of complex life were buried at the base of the submerged precipice. Some 80 million years ago a subduction zone formed off the coast as the Farallon Plate started to dive below the North American Plate; volcanoes and uplifting mountains were created in the region as a result. Stretching of the crust under western North America started around 16 mya, creating the Basin and Range province. By 2 to 3 mya this province had spread to the Death Valley area, ripping it apart and creating Death Valley, Panamint Valley and surrounding ranges. These valleys partially filled with sediment and, during the wet times of ice ages, with lakes such as Lake Manly. By 10,500 years ago these lakes were increasingly cut off from glacial melt from the Sierra Nevada, starving them of water and concentrating salts and minerals. The desert environment seen today developed after these lakes dried up.

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