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<br />0'> <br />It) <br />,",.I <br />C' <br /> <br /><.:. <br /> <br />CHAPTER II <br /> <br />UNIT SETTING <br /> <br />The Grand Valley Unit area parallels the Colorado River and occupies <br /> <br />an area roughly 12 miles wide and 35 miles long. The valley is charac- <br /> <br />terized by agriculture--primarily livestock, feed crops, and fruit <br /> <br />orchards--and by increasing urban and light industrial development. <br /> <br />Natural Environmental Characteristics <br /> <br />Land forms and geology <br /> <br />The Grand Valley is bounded on the north and northeast by the Book <br /> <br />Cliffs, on the south and southwest by the northern tip of the Uncompahgre <br /> <br />Plateau, and on the southeast by Grand Mesa, a flat-topped, basalt-capped <br /> <br />mountain over 10,000 feet in elevation. <br /> <br />The elongated valley is rela- <br /> <br />tively flat, sloping gently upward to the northeast to low rolling hills <br /> <br />near the Book cliffs. <br /> <br />To the southwest, the Uncompahgre Plateau rises <br /> <br />above the valley floor, while two large low-lying mesas separated by the <br /> <br />Gunnison River are prominent to the south and southeast. One, the <br /> <br />relatively flat Orchard Mesa, is situated at the foot of the Grand Mesa; <br /> <br />the other, a rolling mesa known as the Redlands, lies west of the Orchard <br /> <br />Mesa at the foot of the Uncompahgre Plateau. <br /> <br />Lands within the valley <br /> <br />range in elevation from 4,400 feet to 4,700 feet. <br /> <br />The Colorado River has eroded the Grand Valley from the Mancos <br /> <br />Formation, a sequence of thick beds of gray calcareous Marine Shale which <br /> <br />contains a high percentage of salt and is fractured and jointed near the <br /> <br />surface. During the weathering process, salts in the shale are dissolved <br /> <br />and redeposited in the joints and bedding planes of the weathered shale. <br /> <br />6 <br />