Grand Canyon: Geology and history of the canyon
Layer upon layer of different rocks, readily distinguished by color, and each with its own fossil record, recede down into the Grand Canyon and back through time, until the strata at the river bed are among the oldest exposed rocks on earth. And yet how the canyon was formed is a mystery. Satellite photos show that the Colorado actually runs through the heart of an enormous hill (which native Americans called the Kaibab , the mountain with no peak); experts cannot agree on how this could happen. Studies show that the canyon still deepens, at the slow rate of 50ft per million years. Its fantastic sandstone and limestone formations were not literally carved by the river, however; they're the result of erosion by wind and extreme cycles of heat and cold. These features were named - Brahma Temple, Vishnu Temple , and so on - by Clarence Dutton, a student of comparative religion who wrote the first Geological Survey report on the canyon in 1881.While it may look forbidding, the Grand Canyon is not a dead place. All sorts of desert wildlife survive here - sheep and rabbits, eagles and vultures, mountain lions, and, of course, spiders, scorpions and snakes. The human presence has never been on any great scale, but signs have been found of habitation as early as 2000 BC, and the Ancestral Puebloans were certainly here later on. A party of Spaniards passed through in 1540 - less than twenty years after Cortés conquered the Aztecs - searching for cities of gold, and a Father Garcés spent some time with the Havasupai in 1776. John Wesley Powell 's expeditions along the fearsome and uncharted waters of the Colorado in 1869 and 1871-72 were what really brought the canyon to public attention. A few abortive attempts were made to mine different areas, but facilities for tourism were swiftly realized to be a far more lucrative investment. With the exception of the Indian reservations, the Grand Canyon is now run exclusively for the benefit of visitors; although even as recently as 1963 there were proposals to dam the Colorado and flood 150 miles of the Canyon, and the Glen Canyon dam has seriously affected the ecology downstream.
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