104 A. HAGUE THERMAL WATERS IN YELLOWSTONE PARK 



is taken that superheated waters issuing from igneous rocks are primitive 

 in their origin — that is to say, they are derived from great depths in the 

 earth^s crust and are brought to the surface for the first time by volcanic 

 forces. 



The Yellowstone National Park affords one of the most remarkable, 

 and probably one of the most instructive, areas of thermal springs and 

 geysers to be found in the world. The varied phenomena of boiling 

 springs and aqueous vapors there stand unsurpassed. Several years ago, 

 after a study of the region under the auspices of the United States Geo- 

 logical Survey, I published in official documents, and later in Johnson's 

 Universal Cyclopaedia, an article entitled "Thermal Springs," in which I 

 stated the conclusion that the waters of these hot springs and geysers 

 were essentially meteoric waters that had penetrated downwards a suffi- 

 cient distance to attain an increased temperature, only to be forced again 

 to the surface by ascending currents. 



I propose on this occasion to present briefly some of the geological evi- 

 dence on which these conclusions are founded. They are based on the 

 nature and structure of the rocks through which the heated waters reach 

 the surface, the mineral constituents contained in the waters, the compo- 

 sition of the associated gases, and the characters of the varied sediments 

 and incrustations deposited around the springs and pools. 



Eocene Igneous Eocks 



To understand correctly the relations of the thermal waters found in 

 the park to existing geological conditions, a brief history of the salient 

 features of its igneous rocks and their sequence seems necessary. The 

 country included within the Yellowstone Park, the Absaroka Eange, and 

 the Wind Eiver Plateau consists essentially of masses of igneous rocks 

 covering an area of over 5,000 square miles in the center of a conti- 

 nent whose three great rivers, the Mississippi, the Colorado, and the 

 Columbia, here find their source. Within this region, through that vast 

 period of time from the close of the Archean to the dawn of the Tertiary, 

 all evidences of eruptive energy are wanting. Coincident with the ear- 

 liest indications of the post-Laramie erogenic movement came a period 

 of intrusion which began in late Cretaceous time and continued with 

 only slight periods of rest till near the end of the Pliocene. Whatever 

 the primary causes were that produced this erogenic movement, the en- 

 largement of the continental area, and the final withdrawal of the sea, 

 they brought about mountain uplifts, crustal displacements, and volcanic 

 activities of the first magnitude. The close of the Cretaceous in this 

 pait of the northern Cordillera was marked by the most profound strati- 



