A Geological Odyssey by Denise Bicknell - Part 2 Today we say goodbye to Colorado and hello to Utah. We entered Utah on I-70 and drove the 20 or so miles to highway 128 south headed for Arches National Park. This area is characterized by mesas and cliffs. The Book Cliffs to the north are composed of sandstone, shale, and coal. To the south the landscape is also marked by shale and sandstone. The Colorado River enters Utah heading southwest, carving its way through the sandstone and creating a gorge. The drive from I-70 to US 191 provides a pretty good taste of those features. At times the roadway seems as if it is one with the river, twisting and turning to push its way through layers of sedimentary rock. There are great boulders of sandstone resting near the highway that have been weathered off and tumbled from the cliffs above, like a pile of blocks a child might have played with then abandoned. The river flows peacefully along on the west side of the road making one wonder at its great erosive power. In places the walls of the gorge are stained with the dark coloration of desert varnish, looking all the like someone threw a bucket of paint at them, its running down their faces like icing dripping down the sides of a warm cake. Desert varnish is a thin layer of manganese, iron oxide, and clay precipitated by bacteria that thrive in arid climates on smooth surfaces. The clay helps to protect the microbes from the harsh environment. All that varnish makes one wonder at the great numbers of tiny bacteria present. We stopped at an overlook and took photos of the desert varnish streaked canyon walls, the Colorado River, and the kids climbing on some of those great boulders.
Posted on: Sat, 30 Aug 2014 03:49:34 +0000
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