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Geology

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Canyonlands National Park Service U.S. Department of the Interior Canyonlands National Park Geology Canyonlands National Park is a showcase of geology. In each of the park’s districts, visitors can see the remarkable effects of millions of years of erosion on a landscape of sedimentary rock. Pictured above, the Green River has carved a channel out of rock layers deposited nearly 300 million years ago. Deposition Most of the rock found in Canyonlands today came from distant mountain ranges like the ancestral Rockies and even the Appalachians. For millions of years, rock was broken down and carried here by wind and water, creating deposits that eventually became distinct layers of sedimentary rock. Some layers were laid down by rivers, their sandy channels surrounded by swamps and Uplift Many of the rocks exposed in Canyonlands were deposited near sea level. Today, the average elevation here is over 5,000 feet above sea level – a significant uplift. Canyonlands is part of a region called the “Colorado Plateau,” an area that stands high above the surrounding country. About 20 million years ago, movement in the Earth’s crust began to alter the landscape of North America, building modern landforms like the Rocky Mountains, Nevada’s Basin and Range, and the Colorado Plateau. Some geologists Erosion Today’s landscape is one of erosion. As this area gradually rose, rivers that once deposited sediment on the lowlands began to remove it from the emerging plateau. The Green and Colorado Rivers began carving into the geologic layer cake, exposing buried sediments and creating the canyons of Canyonlands. However, the rivers aren’t the only force of erosion. Summer thunderstorms bring heavy rains that scour the landscape. Some layers erode more easily than others. As softer rock dissolves away, layers of harder rock form exposed shelves, giving the canyon walls their stair-step appearance. Occasionally, a slab of harder rock will protect a weaker layer under it, creating balanced rocks and towers. Great examples of this are visible in Monument lakes. Wind brought some of the thickest layers, creating vast sand deserts or dune fields on the shores of an ancient sea. The accumulating rock created a geologic layer cake, with most of the material hidden below the surface. There were no canyons: only vast plains gently sloping into the distance. But change was coming... believe that the plateau has risen as much as 10,000 feet since the uplift began. These movements also created cracks where melted rock rose from deep inside the Earth. In some places, it cooled before reaching the surface, creating pockets of harder, igneous rock within the surrounding sedimentary layers. Eventually, erosion exposed these harder deposits, creating the isolated mountain ranges visible from Canyonlands: the La Sals, Henrys and Abajos. Basin at the Island in the Sky and the Land of Standing Rocks in the Maze. Water also seeps into cracks in the rock, eroding and widening them until only thin spires remain, like those found in the Needles. As the work of erosion continues, today's geologic displays will eventually disappear, making way for future wonders. Rock Sequence of the Canyonlands Area TERTIARY This sequence shows the deposited layers from youngest (top) to oldest (bottom). For clarity, the entire record of visible layers in this area is shown, including those not found in Canyonlands. Older rocks are not exposed in southeast Utah, except for Precambrian rocks along the Colorado River in Westwater Canyon. Geologic names are actively debated and vary regionally, so sometimes two names are listed. Descriptions of the dominant layers 1.6 in Canyonlands National Park: C R E TA C E O U S 66 Navajo Sandstone Sandstone. Desert sand dune environment with periodic flooding. Heavily crossbedded, some dinosaur tracks. Forms tan cliffs and domes. Island in the Sky mesa top, Horseshoe Canyon. Abajo, Henry, La Sal Mountains Green River FM Uinta Basin Source of oil Wasatch/Claron FM Bryce Canyon NP (hoodoos) Book Cliffs Source of coal Mesa Verde Group Kayenta Formation Sandstone, siltstone, with limestone and shale. Dinosaur tracks and ripple marks sometimes visible. Meandering river environment. Forms ledges and slopes. Island in the Sky mesa top. Badlands along I-70. Mancos Shale Wingate Sandstone Dakota Sandstone Cedar Mtn/Burro Cyn FM Mesa tops, canyons at Hovenweep NM Sandstone. Desert sand dune environment. Forms prominent red cliffs and spires in the canyonlands basin. Island in the Sky, Candlestick Tower, the Orange Cliffs. 144 Source of Uranium and Dinosaur Tracks throughout SE Utah and SW Colorado San Rafael Group Glen Canyon Group JURASSIC Morrison Formation Summerville Formation Curtis Formation Exposed along the Green River Delicate Arch Arches NP Entrada Sandstone Horseshoe Cyn. Trailhead Carmel Formation White Rim Sandstone Sandstone. Desert/near-shore sand dunes with periodic flooding. Forms cliffs and caprocks. Prominent white canyon rim at the Island in the Sky, also spires and towers in Monument Valley. Kayenta Formation Wingate Sandstone Organ Rock Shale Chinle Formation Sandstone, shale, siltstone. Deposited in streams and tidal flats. Forms red slopes and, when protected from weathering, standing rocks. Monument Basin, Land of Standing Rocks. Moenkopi Formation Cedar Mesa Sandstone TRIASSIC 245 White Rim Sandstone Cutler Group PERMIAN Moenkopi Formation Sandstone, siltstone. Tidal flat environment. Ripple marks and mud cracks are often visible. Forms red/brown slopes with occasional ledges. Basins below Island in the Sky mesa top. Navajo Sandstone 208 Organ Rock Shale Halgaito Shale/Elephant Canyon Formation Group Conglomerate, limestone, sandstone, siltstone, shale. Shallow coastal marine environment. Forms cliffs and slopes. Below Big Spring Canyon Overlook in the Needles District. Undivided Cedar Mesa Sandstone 286 Honaker Trail Formation Hermosa Group Sandstone. Near-shore sand dunes (white) interfingered with periodic river/lake deposits (red). Forms cliffs, domes and pinnacles. Dominant layer in the Needles and Maze Districts. Cutler Halgaito Shale/Elephant Canyon Formation P E N N S Y LVA N I A N Chinle Formation Bentonite clay, conglomerate, sandstone, shale and siltstone. Deposited by meandering rivers, shallow lakes and swamps. Moss Back Member contains petrified wood and Uranium. Forms colorful slopes with occasional ledges. Honaker Trail Formation Fossiliferous limestone, sandstone, shale. Shallow sea, delta and stream environments. Forms cliffs and slopes. Inner canyon of the Colorado and Green Rivers Paradox Formation Paradox Formation 320 GEOLOGIC PERIOD Millions of Years Ago Dolomite, gypsum, limestone, potash, salt and shale. Shallow,restricted inland sea with repeated evaporite cycles. Forms cliffs, gypsum and salt domes. Printed by Canyonlands Natural History Association, 12/12 5m EXPERIENCE YOUR AMERICA

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