Week Three: Evidence of Plate Tectonic • Welcome to Big Cottonwood Canyon! • According to Utah Geological Survey: “ The Best know fault line in Utah is the Wasatch Fault, which crosses or passes near the mouths of the Wasatch Front Canyons.” The Big Cottonwood Canyons shows great example of tectonic plates with the use of Thrust Fault-results from compression forces that shorten and thicken the crust. Movement is horizontal, where older rock are pushed over younger rocks. Mr.Raymond trust fault trends through Big Cottonwood Canyon. Evidence of Thrust Fault in Utah(Picture and source is Utah Geological Survey). Location: Mountain Home Range, Utah. The second evidence of plate tectonic is tilted rock layers. • “Tilted rock layers- you can see as you drive up and down Big Cottonwood canyon many different examples of this. You see rock layers that are straight up and down, where farther up the canyon they are a little more slanted, obviously showing that there has been movement and growth and not that they are sitting there not moving.” (Source-Utah Geological Survey) Tilted Layers of rock, started at the entrance of the canyon. Location: 40.6410° N, 111.6890° W Location: Big Cottonwood Canyon, Utah 40.6410° N, 111.6890° W Slates and quartzites are exposed in lower Big Cottonwood canyon at the geologic road sign "Storm Mountain Quartzites", about 3 miles from the mouth of the canyon. The black slates and "rusted"quartzites are part of the Big Cottonwood Formation, and are about 900 million years old (Source: Hintze, 1988). The is a spot in Big Cottonwood canyon, 1.5 miles up on the south side where there is a good showing of the layers of rock being tilted. One more example of layer tilting. Location: 40.6410° N, 111.6890° W