blackfoot-valley

miles upstream, enough to give the river a rapid flow where it passes through Ranch land. Its steepest gradient and therefor fastest flow is where it appoach- es Raymond Bridge that marks the north end of the property. The Blackfoot is a major tributary of the Clark Fork of the Columbia River, joining it at Milltown a few miles upstream from Missoula. After the Clark Fork is joined by the Bitter- root and Flathead rivers below Missoula, that stream actually has a volume of flow greater than that of the much longer Missouri and Yellowstone rivers com- bined where they join just across the Montana / Dakota line. Most of the Ranch land where cattle are grazed in greatest numbers lies at elevations of 4,300 to 4,400 feet above sea level, although the upper Mur- ray and Douglas creeks in the large leased area of the Ranch’s southern sec- tion flow down from over 5,500 feet with mountain slopes rising above them to 7,000 foot elevations. Land everywhere in the world is shaped mainly by three agents: pres- sures and tensions of tectonic (earth crustal) movements which may push land upward to form high country from which mountains are carved; erosion which does the carving; and the depositing of material constantly eroded from the higher land. (Volcanic activity can be regarded as a special case of deposition.) The great regional uplift that formed the basis for the Rocky Mountains began close to 200 million years ago, long before any human beings existed on earth (even small primitive mammals were just beginning to develop). The Rocky Mountain System and the associated Pacific Mountain System are the youngest mountains of the Americas; their uplift still continuing as four main Pacific crustal plates continue to push against the continental plates. This ex- plains why these mountains are also the continent’s highest, since erosion has not yet had time to reduce them to mere “hills”. In the larger sense, North and South America are all part of the same system. The Andes on South America’s Pacific side rise even higher than the Rockies; and, on the east side of both continents, lower old worn-down mountains - the “hills” - show up beyond extensive intervening plains, as the Appalachian system in North America and Brazil’s Atlantic highlands in the southern continent. The agents of both erosion and deposition are, in order of increasing im- portance: wind, ice, and especially liquid water. Water, whether in the form of myriad temporary freshets or more dramatic flooding, is responsible for carving Shaping the Land 15