(i.) The Yellowstone Park.—The geysers and hot springs of the Yellowstone Park, like those in Iceland and New Zealand, are special manifestations of volcanic action, generally in its secondary or moribund stage. The geysers of the Yellowstone occur on a grand scale; the eruptions are frequent, and the water is projected into the air to a height of over 200 feet. Most of these are intermittent, like the remarkable one known as Old Faithful, the Castle Geyser, and the Giantess Geyser described by Dr. Hayden, which ejects the water to a height of 250 feet. The geyser-waters hold large quantities of silica and sulphur in solution, owing to their high temperature under great pressure, and these minerals are precipitated upon the cooling of the waters in the air, and form circular basins, often gorgeously tinted with red and yellow colours.[11]
[1] J. W. Powell, Exploration of the Cañons of the Colorado, pp. 114, 196. Major Powell describes a fault or fissure through which floods of lava have been forced up from beneath and have been poured over the surface. Many cinder-cones are planted along the line of this fissure.
[2] Capt. C. E. Dutton. Sixth Ann. Rep. U.S. Geol. Survey, 1884-85.
[3] Dutton, loc. cit., chap. iv. p. 165.
[4] Amer. Jour. Science, vol. 3., ser. (1871). A beautiful map of this mountain is given in the Fifth Annual Report, U.S. Geol. Survey, 1883-84. Plate 44.
[5] Daubeny, loc. cit., p. 474.
[6] Gilbert, Monograph U.S. Geol. Survey, vol. i. (1890).
[7] Powell, Exploration of the Colorado River, p. 177, etc. (1875). Hayden, Rep. U.S. Geol. Survey of the Colorado, etc. (1871-80).
[8] Richthofen, Natural System of Volcanic Rocks, Mem. California Acad. Sciences, vol. i. (1868).
[9] Geikie, Geological Sketches at Home and Abroad, p. 271 (1882).