194 



EARTH FEATURES AND THEIR MEANING 



soap, as was accidentally discovered by a Chinaman who was uti- 

 lizing the geyser water in the Yellowstone Park for laundry opera- 

 tions. After this discovery it became a common custom to 

 " soap " the Yellowstone geysers in order to make them play; 

 but this method was prohibited under heavy penalty after the dis- 

 astrous eruption of the Excelsior Geyser. 



The deposition of siliceous sinter by plant growth. Geysers 

 are known only from areas of siliceous volcanic lava, and this may 



perhaps have its cause in the easier 

 solution of the geyser tube from 

 such materials. The silica dis- 

 solved in the heated waters is 

 again deposited at the surface to 

 form siliceous sinter or geyserite. 

 This material forms terraces sur- 

 rounding the geysers or is built up 

 into mounds which are often quite 

 symmetrical, such as those of the 

 Bee Hive and Lone Star geysers 

 of the Yellowstone Park (Fig. 204). 

 The greater part of this sepa- 

 ration of silica from the heated 

 geyser waters is due to the action 

 of plants or algae that are able 



to grow in the boiling waters and which produce the beautiful 

 colors in the linings to the hot springs. The wonderful variety 

 of the tints displayed is accounted for by the fact that the algae 

 take on different colors at different temperatures. The silica 

 is deposited from the water in the gelatinous hydrated form, which, 

 however, dries in the sun to a white sand. The growth within the 

 pools goes on in a manner similar to that of a coral reef, the algae 

 dying below and there becoming encased in the rock lining while 

 still continuing to grow upon the surface. Whereas sinter of this 

 nature, when deposited by evaporation alone, can produce a maxi- 

 mum thickness of layer of a twentieth of an inch each year, the 

 growth from alga deposition within limited areas may be as much 

 as eight inches during the same period. 



FIG. 204. Cone of siliceous sinter 

 built up about the mouth of the 

 Lone Star Geyser in the Yellow- 

 stone National Park. 



