Paper: An Analysis of the Geologic History of Zion Canyon

Zions elevation rose from sea level to as high as 10,000 feet above sea level. This uplift gave the streams greater cutting force in their decent to the sea. Zions location on the western edge of this uplift caused the streams to fall off the plateau, flowing rapidly down a steep gradient. A fast moving stream carries more sediment and large boulders then a slow moving one. These streams began eroding and cutting into the rock layers forming deep and narrow canyons. Since the uplift began the Virginia River has carried away several thousands of feet of rock that were once on top of the layers visible today. At the Temple of Sinawava the water erodes the shale, causing the sandstone to collapse and widening the canyon. The river also cuts through the Navajo Sandstone , creating a slot canyon. Alandslide once dammed the Virginia River forming a lake. Sediments settled out of the quiet waters and covered the lake bottom. When the river breached the dam and the lake drained, it left behind a flat bottomed valley (http://zion.areaparks.com/parkinformation.html?content=geology). The rivers job of sculpting the canyon is made easier by the nature of the sandstone. Sandstone consists of grains of quartz that are held together with a weak cement that is readily dissolved by water. Tiny particles are loosened and then swept away by wind or water. Also adding to the ease of the erosion process are cracks in th sandstone or joints that allow water to run and cut deeply into the sandstone. Nearly vertical monoliths and precipitous canyon gorges are evidence that Zion is geologically young. Zion has developed its characteristics within the last few million years, its formations are considered Mesozoic (a relatively short period of time in the life span of rock). Zion keeps changing every year. Erosion continues and will someday far in the future reduce the magnificent landscape of Zion to flat plains....