Glen Canyon National Recreation Area - Environment
The spectacular landscape dominating this canyon country is the product of eons of geologic activity: shifting of continents, global rising and falling of sea levels, and creation of highlands now worn and redeposited. At times, desert dominated the landscape; sometimes, freshwater or saltwater seas invaded, leaving rivers to erode the most recently deposited layers. Prevailing winds abetted the process. Periods of erosion account for missing rock strata, layers appearing elsewhere in sequence. The last uplift of the Colorado Plateau began about 60 million years ago. Uplift made meandering streams of the Colorado River run faster and cut the canyons that are Lake Powell's basin. Navajo sandstone, the dominant formation, is made of sand dunes hardened by pressure from deposits above them. The deposits eventually wore away and exposed today's sandstone. Other layers contain sea-deposited sediments; still others hold fossils of land or marine organisms that lived millions of years ago. Petrified wood and fossils ofdinosaur bones, seashells, and small sea creatures are found in several rock strata in thisarea.Most plants and animals found here are typical of desert species. Cactus, yucca, blackbrush, rabbitbrush, and grasses dominate desert plant communities. Spring or summer precipitation prompts sand lilies, fleabane, evening primrose, lupine, Indian paintbrush, and globe mallow to bloom. Pinyon and juniper trees grow at higher elevations. Animal inhabitants include coyotes, foxes, rats, mice, lizards, and insects. In startling contrast, shaded spring-fed alcoves in side canyons provide suitable habitat for deer and beaver, ferns and sedges, reeds and cattails, cottonwoods and willows. Ravens, eagles, hawks, owls, sparrows, and swallows are regular residents of the canyon country, where canyon wrens sing their unforgettable song.
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