THE WORK OF GROUND WATER 



6 7 



by adding new material to others. This is due to the fact that hot 

 water is a more powerful solvent than cold. 



Geysers. — Geysers are springs which intermittently erupt col- 

 umns of hot water and steam (Fig. 43). They occur in regions of 

 comparatively recent volcanic activity, where the lava is hot at a 

 relatively shallow depth. They are well developed in but three lo- 

 calities in the world, and the total area occupied by them is probably 

 less than ten square miles. The most notable geysers occur in Ice- 

 land, New Zealand, and the United States, although smaller ones are 

 to be seen in Mexico, Tibet, 

 the Azores, and the island 

 of Formosa. Some of them 

 throw water to a great height. 

 The Monarch Geyser in New 

 Zealand became active in 

 1903 and is said to have 

 thrown mud and stones to a 

 height of 1000 feet. Such a 

 height, however, is unique. 

 In the Yellowstone National 

 Park an eruption throwing 

 water 300 feet vertically is 

 rare. 



The quantity of water 

 flowing from geysers varies 

 greatly : in the smaller ones 

 it may be only a few gallons 

 an hour, while in others, as 

 in Old Faithful in the Yellowstone National Park, the discharge may 

 be as great as 750,000 gallons an hour, a quantity sufficient to supply 

 a city of 150,000 inhabitants. The water of geysers is rain water 

 which has percolated through porous lava, and under normal condi- 

 tions would be discharged as springs. Consequently, if the climate 

 of the Yellowstone National Park should become arid, the geysers 

 would disappear. This water, heated by its passage through the 

 lavas, dissolves soda and potash, becoming alkaline and thus capable 

 of dissolving silica from the silicates of the lavas. Accordingly, 

 the waters erupted by geysers contain much mineral matter in solu- 

 tion, the chief of which is silica. This silica is deposited about the 

 openings of the springs as siliceous sinter, or geyserite, forming a 



43 



Lone Star Geyser, Yellowstone 

 National Park. 



