GEYSER 



2486 



GEYSER 



sense we cannot dedicate, we cannot consecrate, 

 we cannot hallow this ground. The brave men, 

 living and dead, who struggled here, have conse- 

 crated It far above our poor power to add or 

 detract. The world will little note, nor long re- 

 member, what we say here, but It can never forget 

 what they did here. It is for us, the living, 

 rather to be dedicated here to the unfinished work 

 which they who fought here have thus far so 

 nobly advanced. It is rather for us to be here 

 ^dedicated to the great task remaining before us, 

 that from these honored dead we take increased 

 devotion to that cause for which they gave the 

 last full measure of devotion, that we here 

 highly resolve that these dead shall not have died 

 in vain, that this nation, under God, shall have 

 a new birth of freedom, and that government of 

 the people, by the people, for the people, shall not 

 perish from the earth. 



GEYSER, gi'ser, or gi'zer. In the volcanic 

 regions of Iceland, New Zealand and Yellow- 

 stone National Park there are very striking 

 exhibitions of the earth's internal heat in the 

 wonderful natural fountains, called geysers, 



DIAGRAM OF GEYSER 



Showing the tube and one of the fissures for 

 supplying the tube. 



from which streams of boiling water and steam 

 shoot high into the air at varying intervals. 

 Geysers have often been compared to volca- 

 noes, for they act much the same, but instead 

 of molten rock, they shoot forth water con- 

 taining silica in solution. 



Origin and .Action. Geysers form along the 

 lines of drainage, that is, near rivers and 

 lakes, from the surface water which works 

 down through cracks in the rocks and lava, 



until, at some unknown depth, it comes in 

 contact with rocks sufficiently hot to boil it. 

 The rocks are much hotter than is necessary 

 to heat the water to the boiling point, and as 

 more water trickles down, the pressure of the 

 cooler water near the surface becomes very 

 great on the boiling water beneath. 



When the pressure of the steam formed at 

 the bottom becomes stronger than that from 

 above, the steam must escape, so it forces the 

 water above it up through an opening in the 

 rocks, called a tube. As soon as a little of the 

 water overflows upon the surface of the earth 

 the pressure below is relieved, and the steam 

 shoots out, taking a great amount of water 

 with it. The eruption occurs very suddenly, 

 and after it ceases much of the water which 

 falls around the geyser evaporates, leaving 

 deposits of silica or lime carbonate that often 

 take on beautiful and fascinating forms. 



Some geysers, such as the Giantess in Yel- 

 lowstone National Park, never form cones, but 

 appear as pools of wonderfully clear water, 

 except when in action. Very little water is 

 left after an eruption in those which have 

 cones, except in such cases as that of the tiny 

 Model, also in Yellowstone National Park, 

 where all the water ejected falls back into the 

 cuplike cone and returns to the depths of 

 the earth to be reheated. The eruption of 

 geysers is caused by the gradual filling of the 

 crater with water, which is forced up by the 

 steam generated in the cavity below. The 

 water prevents the escape of the steam, and 

 as it rises in the crater, the pressure of steam 

 below increases. Finally, the water reaches 

 the top of the crater, and begins to overflow. 

 With the overflow the pressure in the crater 

 lessens and the steam under high pressure ex- 

 pands with such force as to drive all the water 

 out of the crater, often throwing it over a 

 hundred feet into the air. After the water has 

 been expelled a flow of steam follows for sev- 

 eral minutes. The geyser then becomes quiet 

 and remains in this state until the crater is 

 again filled, when another eruption occurs. 



In course of time geysers cease to act and 

 become hot springs. However, this process is 

 very slow and the formation of new geysers 

 offsets the decay or drying up of old ones, so 

 that it will be thousands of years before they 

 cease to exist. The prevalent idea that gey- 

 sers erupt at regular intervals is false, al- 

 though a few geysers, such as Old Faithful 

 in Yellowstone Park, send forth their shower 

 at somewhat definite periods. 



