Roadside Geology of Utah
Felicie Williams, Halka Chronic
Format: PDF / Kindle (mobi) / ePub
Arches National Park. Bryce Canyon. Zion. When one thinks of Utah, it’s rocks and iconic landforms—preserved in a nearly endless list of national parks and monuments—come immediately to mind. Perhaps more so than any other state, Utah is built for geologic exploration, and geologists/authors Felicie Williams, Lucy Chronic, and Halka Chronic are its expert tour guides.
The Beehive State is splitting at the seams with wondrous geological contrast. Utah’s high mountains, showcasing the results of what happens as the Earth bends, folds, and breaks itself apart, run like a backbone down the center of the state. To the east, the Colorado Plateau’s flat-lying sedimentary rock is wondrously exposed in canyons, arches, and breaks. To the west is the immense Great Basin, a region characterized by rank upon rank of long, narrow, gaunt mountain ranges alternating with desert basins that are among the flattest surfaces on Earth.
Roadside Geology of Utah’s 65 road guides traverse the state’s major thoroughfares as well as its dusty, sleepy, winding two-lane highways. With fresh prose and more than 300 color photos, maps, and figures to boot, you too will become expert at reading Utah’s rocks.
topped with Pleistocene gravel. In the monuments of Monament Valley, steep walls of Permian Cedar Mesa sandstone rise above softer Organ Rock shale, also Permian. N � 10 0 0 10 20 20 30 MILES KILOMETERS us 1 63 ARIZONA - B L U FF Eroded by wind and rain, soft red shales undermine strong, vertically jointed sandstone to produce many free-standing buttes and pinnacles. ments are made of another Permian formation, the Cedar Mesa sandstone. This dune sandstone, like man others, tends to
Dale gets its name from the castellated turrets on the sides of some of the Quaternary terraces edging the valley. Formed of fine sediments containing volcanic ash, many of these terraces are no longer connected with the mountains they once flanked, but stand as isolated, steep-sided mesas. Where the Book Cliffs approach the highway, a roadcut exposes the contact between dark gray Mancos shale and overlying Mesaverde siltstone, sandstone, and thin coal seams. In the background the contact falls
exposed in roadcuts above Rockport Reservoir. �..... Pal�ozoic rocks are thrust eastward over Jurassic and Creta ceous rocks as part of Utah's great overthrust. N t 20 MILES 10 0 i o•••,� 0 �� 20iiiiii ii �ii 3�0�KILOMETERS 1 22 1-80/1-84 LOOP SALT LAKE CITY - UINTAH � �� J � Interstate 80/84 loop Salt Lake City-Uintah 83 miles/135 km. Crossing delta deposits that mark the edge offormer Lake Bonneville and also conceal the exact position of the Wasatch fault, Interstate 80 plunges
one of the breaks typical of the edges of the Markagunt Plateau. The highway climbs through a lava dam and into the upper part of the East Fork's valley between mileposts 96 and 97. The natural dam and the sediments it held back are responsible for the fertile fields farther north. The Sevier fault is still with us, at the base of the Paunsaugunt Plateau to the east. Bryce Canyon lies on the other, eastern side ofthis plateau. Rocks that surface the Paunsaugunt Plateau appear at highway level
knife; pure, dense gypsum, sometimes tinted pink, is known as alabaster. East of the Arapien shale hills the route enters a volcanic area of lava flows, breccia, and light-colored volcanic ash. Most of the rock is breccia - broken fragments ofvolcanic rocks mixed with volcanic ash. This massive rock forms much of the north end of the Sevier Plateau, which the highway crosses here. Unusually deep gullying in fine river-deposited sediments of the valley floor near milepost 1 8 is probably due to