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<br />3.G <br /> <br />Units E and F are composed of volca~ic rock. Unit E includes a layer of <br />highly fractured rock that supplies most of the material to the talus deposits <br />and rock glaciers found near the upstream boundal"y of the Cornet Creek watershed. <br />Unit F is a very hard and erosion-resistant <br />The source area for the mud flows is the deposit of glacial drift that <br />extends approximately 6,000 feet upstream fr~m the northern edge of the town. <br />The glacial drift is composed of rock eroded from the upper portion of the <br />watershed and includes materials derived from the volcanic formations and <br />Telluride Conglomerate found upstream of the drift. Glaciation during the <br />Pleistocene epoch (0.01 to 1.6 MY ago) eroded the material from the upper part <br />of the watershed and left deposits of glacial drift at both the head and near <br />the mouth of Cornet Creek. Consequently, mud flows supplied by the deposit of <br />glacial drift would contain rocks from the upper part of the watershed. The <br />rocks from the upper part of the watershed, ho\/ever, were brought to the mud flow <br />area by glacial action, not by mud flows from the head of the valley. <br />Figure 3.4 is a photograph of the hea~Maters area of Cornet Creek. The <br />light-colored, fan-shaped deposits at the base of the cliffs in this picture are <br />t.alus deposits. A rock glacier is also visible at the base of the cliffs, <br />located slightly right of center in the photograph. The hummocky terrain in"the <br />foreground is a deposit of glacial drift, <br />The all uvi a 1 fan at the mouth of Cornet Creek is composed of a lluv i a 1 <br />materials and mud flow deposits from the Cornet Creek watershed. The extent of <br />these alluvial deposits indicate that mud flm~s from this drainage are a normal <br />part of the geomorphic history of t.he Cornet Creek watershed. Large mud flows <br />from the Cornet Creek watershed caused serious damage to the town of Telluride <br />in 1914 and 1969, and can reasonably be expected to occur again. <br /> <br />3.2 Soils <br />The dominant mode of rock decomp()~:ition and son development in this <br />environment is shattering due to freeze-thaw cycles. The effectiveness of the <br />chemical and physical processes responsible for soil development is reduced in <br />alpine environments due to cold temperatures and the seasonal variabil ity of <br />available moisture. The dryness of the alpine environment limits the availabil- <br />ity of organi c materi a 1 s for i ncorporat i o~ into the upper soil zone, and also <br />limits the development of clays. Therefore, soils developed in high alpine <br />envi ronments are typi cally very thi n with i nclefi nite zonation. <br />