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PHYSICAL CHARACTER1STICS The eighth largest state in the Union, Colorado has an area of over 104,000 square miles. It has the distinction of being the highest state; with over 50 peaks rising more than 14,000 feet above sea level, Colorado's mean altitude is 6,800 feet. Located near the center of the western half of the U.S., the exhilarating climate and spectacular snow-capped mountains, extensive forests and rolling plains make Colorado a favorite of tourists. CLIMATE Precipitation and temperature are two of the chief ingredients of climate, but their effects are modified by altitude and wind patterns, so portions of Colorado have an alpine ciimate, while other parts are semi-arid. Average annual mean temperatures in the state range from 54'F in the southeast to 33'F in the high mountains, but seasonal extremes may reach as high as 112'F in summer or fall to 50'F below zero in winter. At higher altitudes temperatures fluctuate widely because of the reduced insulating effect of the thinner layer of atmosphere. Prevailing winds from the west or northwest bring moisture from the Pacific Ocean hundreds of miles away. As clouds pass over the high plateaus in the west and approach the mountains they drop most of their moisture, so the eastern part of the state receives scant rainfail. The average annual precipitation in Colorado as a whole is about 16.5 inches, though this varies in different localities from 5 or 6 inches to over 50 inches. Much of the moisture in the mountains comes in the form of snow. At Cumbres Pass the annual snowfall averages over 300 inches, although at Manassa (less than thirty miles away) the average is only about 25 inches. Evaporation is the world's greatest user of water, and in Colorado this is a special problem. Both temperature and altitude affect the rate of evaporation. Water loss from evaporation (total Page 6 moisture lost by plant transpiration, evaporation from the surface of water, snow, soil) may be around 75%. Wind has an extreme drying effect on the soil, and some sections of the state are subject to high winds. Along the eastern slope foothills winds often blow 5 to 15 miles an hour, with occasional gusts ranging from 35 to over 100 miles an hour. GEOLOGY AND TOPOGRAPHY Colorado is divided physically into three major regions: 1) the Great Plains form the eastern 40%, 2) the Rocky Mountains, bisecting the state from north to south, cover about one third of the land area, 3) the western fourth of the state lies in the Colorado Plateau. These divisions generally coincide in both geology and topography as well as in climate. Although they appear flat, the plains slope gently to the east. Layers of sedimentary rock near the surface have a similar slope, but deeper strata may not. Near the northern border are found remnants of a higher prairie where erosion of spring floods and summer thunderstorms have carved the Pawnee Buttes. In the area of transition from prairies to mountains, hills and valleys have been formed by the differential erosion of soft and hard rock layers. This produces such eastern slope landmarks as Castle Rock and Table Mountain, and creates the sawtooth effect known as the Colorado's "hogback" along the exposed edges of the uplifted strata. The Rocky Mountains include several individual ranges or groups of mountains resulting from highly localized movements of the earth crust during the period when the entire region was thrust upward from below. These mountains are frequently interrupted by fractures and slippages (faults). The Front Range is the easternmost and longest continuous uplift in the state extending about 60% of the north-south axis of the state, and including Pike's Peak, Mt. Evans and Long's Peak, each over 14.000 feet above sea level. Toward the south runs the Sangre de Cristo Range which is also punctuated by several 14,000 foot peaks. To the west is another chain of ranges, beginning with the Park Range and Gore Range at the north, and continuing through the Mosquito Range and the Elk Mountains on to the San Juans in the south. Between these ridges lie broad expanses of level, high-altitude valleys: North Park, Middle Park, South Park and the San Luis Valley. The Continental Divide meanders through the mountain area, separating waters and people of the eastern slope from the western slope. Mountain streams frequently glitter with tiny particles of gold, which sparked the Gold Rush of 1859. The mountains contain important deposits of silver, lead, molybdenum and zinc, as well as gold, a