THE PIRACY OF THE YELLOWSTONE 



Ever since the Grand Canyon of the Yellowstone was intro- 

 duced to the general public, it has enjoyed a well-deserved fame 

 for its grandeur and for the unrivaled beauty of its coloring. 

 To the physiographer it has stood as a type preeminent of a 

 very young river valley in the trench stage of development. 

 All who have seen it have been profoundly impressed by it, and 

 by many it is considered the most satisfying object of beauty in 

 the region. It is now possible to introduce this already famous 

 canyon in a new light, as the scene of one of the greatest acts of 

 piracy on record. 



The Yellowstone Lake, with an altitude of 7741 feet A. T., 

 lies in a depression in the southeastern part of the great rhyolite 

 plateau of the Yellowstone National Park. On the east of the 

 lake the land rises rapidly to the high crests of the Absaroka 

 range. On the north and west, and for the most part on the 

 south, the land rises to the general level of the plateau, eight 

 hundred to a thousand feet above the lake. North and south 

 of the lake, and fringing the west shore, are considerable areas 

 of flat land, not far above the present lake level and plainly 

 lacustrine in origin. 



The long southeast arm of the lake is seen to be the lower 

 end of a magnificent mountain valley, here submerged. Beyond 

 the lake the valley extends over thirty miles to the southeast, 

 past the limits of the Park, up into the heart of the Absarokas. 

 The upper Yellowstone River occupies this broad vale, at present 

 wandering on a gradient which compels it to constant deposi- 

 tion, the flat bottom of aggraded material averaging over a mile 

 in width for twenty miles southeast of the lake. This valley is 

 manifestly very old, and it has its counterpart in the Lamar Val- 

 ley in the northeastern part of the Park. It has been shown 1 



1 Arnold Hague : The Age of the Igneous Rocks of the Yellowstone National 

 Park, Am. Jour. Sci., 1896, I, p. 454. 



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