Page:The New International Encyclopædia 1st ed. v. 20.djvu/851

* YELLOWSTONE NATIONAL PARK. 719 YELLOWSTONE NATIONAL PARK. that the waters of the park are scut lo both oceans. South of the Divide the upper course of the Snake lUvc^r receives some of its head- streams from Slioslione, Lewis, and Heart Lakes. North of tile Divide all the streams are tributary to the -Missouri. The most im|)ortant is the Yellowstone (q.v.), which traverses the park from the southeastern corner to the middle of the northern boundary, and e.Kpands into Yel- lowstone Lake, one of the central features of the re<;ion. The Madison River, one of the headstreams of the Missouri, rises on the cen- tral phitcau. while the eastern mountains give rise to the Shoshone, an aliluent of the I!i<,' Horn. The original yeoloyical structure of the park is almost completely hidden by a great Tertiary lava How, the easternmost extension of the Snake River basalt jilains, which are connected to the westward with the. vast Oregon lava fields. The underlying sedimentary rocks are chielly Cre- taceous, probably with some upturned Paleozoic strata and Archaean rocks, but the present pla- teaus and mountains, with the exception of the Gallatin range, are composed of lava, and though there have been no recent outpourings of molten rock, the whole region is still actively volcanic. See Hot .S'/JCiw/.s and Geysers below. Owing to the higli elevation, the climate is rigorous, but not excessively cold compared with the lower surrounding regions. The sum- mer is short and characterized by great diui'nal extremes of temperature, frosts occurring at night even in midsummer. TlLe mean tempera- ture for July is 62°, and the average maximum 78°, the mercury rising occasionally as high as 90°. The growing season does not begin until May, and vegetation reaches its greatest luxuri- ance near the end of July. At the end of August there is an abrupt change from summer to winter, and snow begins to lie on the grouiul l)v the mid- dle of September. In January the mean tempera- ture is about 20°, and the average minimum about 12°, with an occasional fall to 30° below zero. The average annual rainfall on the plateau is about 20 inches, sufficient to support the for- ests and mountain vegetation. Nearly nine-tenths of the area of the park is under forest. Dense forests cover the moun- tains up to an altitude of 9400 to 9700 feet, but on some of the basin floors there are scat- tered open, park-like spaces covered with grass or incrustations from the hot springs. The forests are almost wholly coniferous, although birches, w'illows, and poidars (Popiilits treinu- loides) are not uncommon. The most common tree, and the only one monopolizing extensive forest areas, is the black pine {Pimis Mur- rai/diia), and the second in distribution is the balsam {Abies subalpina), chiefly confined to the higher and moister regions. Engelmann's spruce and the Douglas fir are also common. Irat the trees do not nearly reach the size attained in western Oregon and Vasliington, and the for- ests can scarcely be called grand, though they add in some places a remarkable charm to the scenery. The herbaceous vegetation is chielly that of a mountain flora, though the sage brush occurs on some of the plateaus, and the alpine species above the timber line include nearly all of those common to the Rocky Mountains. The regions immediately surrounding the hot springs have a peculiar flora, partly resembling the xero- phytes of the desert, partly allied to plants found on the seashore. Owing to the protection afforded them, the wild aniinal.s in the park are increasing in num- ber. Elk or wapiti abound, and can be seen in large bauds of several hunilred or even thou- sand. Moose, deer, antelojies, and mountain sheep can also be seen in winter, though in sum- mer they generally retreat to the less frequented mountain regions. L'ntil 1902 there were about 25 head of butTalo (bison) roaming wild in the park, but in that year 22, as many as could be found, were corralled, and 18 others were brought from distant parts of the country. It is the in- tention to improve the breed by this infusion of new blood, and, when the new herd becomes suf- ficiently accustomed to the sight of human be- ings, again to let them loose in the park. Mountain lions (pumas) were seen in the park in 1899, and bears, especially the black and the brown bear, are increasing in numbers. Reavers have also increased, and their dams and houses can be seen on the streams throughout the park. Rirds are scarce, almost the only game birds being a few blue and ruffled grouse. Trout of several varieties are so plentiful in nearly all the streams that with the existing regulations and the hatching and planting of- many thou- sand eggs annually, it will be impossible for the tourists to deplete them. There is probably no region on earth of equal area which excels the Yellowstone Park in the variety of its natural scenery. For the exhi- bition of the beautiful as well as of the grand and merely curious and interesting effects of volcanic forces the region has been uuapproached since the destruction by a volcanic eruption of the 'hite Terrace in New Zealand. Besides the two chief natural features described under sepa- rate subheads below there are a number of minor objects of interest, such as cliffs of obsidian or volcanic glass along the shores of Beaver Lake, the petrified forests found on some of the pla- teaus, and the curious freaks of erosion seen in the mushroom-shaped stone pillars in the 'Hoo- doo Region' and in the natural bridge spanning one of the creeks flowing into Yellowstone Lake. Yellowstone Lake akd Canon. The Yellow- stone River enters the park at its southeastern corner in a marshy valley, and soon flows into the southeastern arm of Yellowstone Lake. The lake lies at an altitude of 7741 feet above sea level, being the largest lake at that altitude in North America, and one of the most beautiful mountain lakes in the world. It-is 20 miles long and 10 miles wide, but of a shape so irregular that it has a shore line of over 100 miles, having sev- eral finger-like arms extending west and south- ward. Its shores are densely forested, and on the east towers a group of numerous lofty peaks in- cluding the highest within the park. Ancient beaches indicate that the lake was formerly much larger and deeper than now, and that instead of discharging into the Yellowstone River and the Atlantic Ocean, it formerly sent its waters to the Pacific Ocean. After leaving the lake at the northern end the river is broad and tranquil for several miles. Then it becomes narrow, rapid, and broken by huge rocks, and, after turning to the northeast, it falls over a precipice 110 feet high, and is narrowed to a width of 100 feet. A half mile below this cataract, which is known as