| OCR Text |
Show , , . ,( .'., -,..,, . ' "v -. - ; ... ' '. ,., ,k- "'. (..rt. . " . . . '"- ;:..,. ' -ijfw I". ),..., ' .. . A , .... . V- i! . -1 ' .-v-v-w'"- s:: . . -: ,, ; t . :p ' ' . .. ' .;; ' . '-;, v.- r i - . -. ,'- ' ' '-v 4 ' ; fr yv .' -.vv...-',--;..". . v Upheaval Dome, in Canyonland.s National Park. Aivial view .shows the concentric rings and arching Upheaval Dome in Canyonlcnds National Park Is Fascinating Study in Geology Ever step on a board lying on muddy ground and see the mud squeeze up through a crack or knothole? knot-hole? Well, much the same thing is happening at Uu-heaval Uu-heaval Dome a great "salt dome" in Canyon-lands Canyon-lands National Park. But here it is salt squeezing up through thick, heavy layers lay-ers of sandstone. A very long time ago, much of this region was covered by a deep salt sea something like a much bigger and saltier Great Salt Lake. Water flowed in from surrounding hills, but there was no outlet. Water flowed in carrying tiny amounts of salt, and as that water evaporated the salt remained in the sea, so that it became more and more salty. Over a long period of time it became so salty that layers lay-ers of salty crystals form- ed. As climatic conditions varied over many thousands thous-ands of years, 2'.) distinct layers of crystalline salt were deposited. They now form a salty bed about 3000 feet thick. As time wore on, the sui rounding hills eroded away and the salt sea disappeared. dis-appeared. Climate and weather patterns varied. At one time or another, lakes, oceans, deserts, swamps, or forests, covered cover-ed the land. Above) the salt beds, other layers were deposited. Mainly sandstone sand-stone in this region, but also shale, limestone, and others, slowly accumulated accumulat-ed until the salt was several sev-eral thousand feet below the surface. The weight of these upper layers exerted exert-ed immense pressure on the salt. ' Salt under great pressure pres-sure will become plastic, and can slowly flow in layers of rock caused by upward bending of deposits de-posits normally found far below the .surface-. fFrom the Canyons . . . Canyonlands Arches Bridges National Park Service Department of the Interior much the same way that solid ice in glaciers will flow due to great pressure. pres-sure. Glacial ice usually flows downhill, however, and the salt had nowhere to go. Nowhere, to go, that is, except up. Here and there in the overlying rock layers were weak points, places where the plastic salt could force its way upward. And under the influence in-fluence of the great pressure pres-sure around it, the salt slowly welled up, building the weakened layers upward up-ward into a dome - like formation. Far above, meanwhile, erosion was stripping away the surface layers. Surface erosion continued contin-ued for thousands of years more an continues contin-ues today, incidentally. Erosion of the surface layers eventually exposed the layers warped by the salt. It cut across the warped layers, too, slicing off the top of the domed rocks above the salt. As the layers had been pushed push-ed sharply up, some are almost verticle. Several of the softer layers were crushed and broken. Erosion has cut a channel chan-nel Upheaval Canyon in one side of the exposed dome. Periodic floods have swept away loose material, mater-ial, leaving a great craterlike crater-like depression about 1500 feet deep and about 3 miles mil-es in diameter. From the air, the concentric rings of rock almost seem to form a huge bullseye. The salt itself, which caused the formation to develop, remains hidden far below be-low the surface. The effect ef-fect of its great force as it was squeezed up like mud through a hole in a board has created a feature fea-ture of great interest. Unique? No, not really. Salt has caused somewhat similar features at over a thousand other sites on the globe. But nowhere else in the world is a salt dome so well displayed as this, nor are the details of any others so clearly seen. Upheaval Dome has a special quality; a strangeness stran-geness all its own. No effect ef-fect of light fails to show its muted rainbow hues, its contrasting shadows, its intricate patterns. No one viewing angle is better bet-ter than another, each just offers you a variation of a single theme. In this land of shapes and shadows of color and light, Upheaval Dome is a feature of primary pri-mary interest on the Is- . land in the Sky. |
