Grand Canyon at Sunset
by Marty Fancy
Title
Grand Canyon at Sunset
Artist
Marty Fancy
Medium
Photograph
Description
Grand Canyon National Park was created on 26 February 1919 by an act of Congress. First protected in 1893 as a forest reserve in which mining, lumbering and hunting continued to be allowed: upgraded to a game reserve in 1906, giving protection to the wildlife: redesignated a National Monument in 1908.
The park is dominated by the spectacular Grand Canyon: a twisting, 1.5 km deep and 445.8 km long gorge, formed during some 6 million years of geological activity and erosion by the Colorado River on the raised Earth's crust (2.5 km above sea level). It divides the park into the North Rim and South Rim which overlook the 200 m to 30 km wide canyon; the buttes, spires, mesas and temples in the canyon are in fact mountains looked down upon from the rims. Ongoing erosion by the seasonal and permanent rivers produces impressive waterfalls and rapids of washed-down boulders along the length of the canyon and its tributaries. Exposed horizontal geological strata in the canyon span some 2,000 million years of geological history, providing evidence of the four major geological eras, early and late Precambrian, Palaeozoic, Mesozoic and Cenozoic. The early Precambrian strata, known as the Vishnu Schist formation, are devoid of fossils. The first fossil evidence appears in the late Precambrian Bass Limestone with remains of early plant forms. Subsequent strata dating from the Palaeozoic era catalogue the sequence of local history, with both marine and terrestrial fossils demonstrating the periods in the distant past when the whole region was alternately submerged and raised. The Mesozoic era is less well illustrated within the park, but tracks made by early reptiles are found to the east in the Navajo Indian reservation. They are a few fossil remains of mammals from the early Cenozoic.
Altitudinal range provides a variety of climates and habitats, ranging from desert to mountain conditions. The canyon is a vast biological museum stretching through five different life and vegetation zones: Hudsonian on the North Rim plateau with Colorado blue spruce and Rocky Mountain maple; Canadian near the North Rim, with aspen and Ponderosa and forests of Douglas fir, white fir and aspen at 2,500 m; high-altitude Transition (Ponderosa) forests of Pinus ponderosa and gambel oak; upper Sonoran on and below the South Rim with Utah juniper, pinon pine and sagebrush; and the Lower Sonoran down the canyon and at the bottom (desert cacti, rabbitbrush, mesquite, Morman tea and Manzanita).
Uploaded
September 20th, 2012
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