OCR Text |
Show less than 18 miles wide. South of the plateaus several terraces form a stair like series of cliffs that rise 4,000 feet in height. The Canyonlands area is characterized by numerous, highly dissected canyons cut by the perennial streams that flow through the area. No other area in the United States has the ruggedness of this area. The Henry Mountains are a predominant feature, rising 4,000 feet above the plateau below to over 11,000 feet. The San Rafael Swell is a mild doming of the strata that has produced inward- facing escarpments on the east side. The top of this dome, San Rafael Knob, rises to almost 8,000 feet above sea level. On the north, the Roan and Book Cliffs rise 3,000 feet to the Tavaputs Plateau. Figure 2 shows the principal land forms of this area. This map was reproduced from " Landform Map of Utah" by Merrill K. Ridd of the University of Utah Geography Department. Topography The topography of an area affects not only climatic factors, but land use, vegetative cover, and runoff. As figure 3 shows, the West Colorado Hydrologic Area is characterized by large variations in topography. The highest point in the area, Mt. Ellen, is 11,615 feet above sea level. The lowest point is Lake Powell which stood at approximately 3,617 feet above sea level in June, 1971. Oil and Gas Fields Oil and gas fields and pipelines are shown on figure 4. Oil reserves in the West Colorado Hydrologic Area are of minor economic importance. Gas reserves are considerably more extensive and contribute substantially to the economy of Carbon and Emery counties. Gas was discovered in the Clear Creek field in 1951 and production through 1962 totaled 106,899,375 cubic feet. Other smaller but significant fields are the Joe's Valley and Flat Canyon fields ( closed in 1958). Coal Deposits Economic minerals in the region are confined mainly to the nonmetallics. Much of the area is underlain by deeply buried Cretaceous strata which is probably coal bearing. There are five fields where important coal seams appear at the surface: Kaiparowits Plateau, Henry Mountains, Emery, Wasatch Plateau, and Book Cliffs fields. These are shown on figure 5. Coal is mined for commercial production in the northern areas of the Wasatch Plateau field at the present time. Local mines are operated in the southern areas of the Wasatch Plateau field. Another small mine is located in the northern part of the Henry Mountains field. Potential exists for future production in other areas. Climate Figure 6 shows normal annual precipitation in inches. Precipitation in this area varies directly with topography. Weather Bureau records from 1931 to 1960 indicate that the average annual precipitation ranges from less than six inches in low lying areas near Green River, Hanksville, and Lake Powell to more than forty inches in the peak areas of the Wasatch Plateau. It should be noted that precipitation in a specific year may vary considerably from the values shown on the map. Precipitation is fairly uniform throughout the year, but a greater amount falls in the October- April period than in the May- September period, especially in the higher elevations. Winter precipitation falls in the form of rain or snow |