146 DYNAMICAL GEOLOGY. 



an indefinite time. If waters,, percolating through these, 

 come up again* after taking up only heat, they form hot 

 springs. If, in addition, they take up CO.,, they form 

 carbonated springs. If lime be taken and deposited on 

 the surface, they form lime-depositing springs (p. 73). 

 If the heat be great, so that vapors are given off and con- 

 densed as clouds, they are called f umaroles. If the waters 

 contain H 2 S, and AlkS, they are called solfataras. If 

 mud is brought up and deposited about the vent, they 

 are mud-volcanoes. Finally, if the springs are periodi- 

 cally and violently eruptive, they are called geysers. The 

 only variety of these springs which need detain us here is 



GEYSERS. 



Geysers may be defined as periodically eruptive springs. 

 They seem also usually, if not always, to deposit silica. 

 They are found only in Iceland, in New Zealand, and 

 in Yellowstone Park. The so-called California geysers 

 are solfataric fumaroles. Steamboat Springs in Nevada 

 may possibly be classed with geysers, but their erup- 

 tions are feeble. The phenomena of true geysers are so 

 splendid that a somewhat full account of them is neces- 

 sary. As they were first studied in Iceland, and the cause 

 of their eruption was first understood there, we will speak 

 of these first. 



Geysers of Iceland. Iceland may be briefly described 

 as a plateau 2,000 feet high, studded with volcanic peaks, 

 with margin sloping gently to the sea. Only the marginal 

 area is to any extent inhabited. The interior is a scene 

 of desolation, where every form of volcanic phenomena 

 exists in the greatest activity volcanoes, hot springs, 

 boiling springs, fumaroles, solfataras, and geysers. Of 

 these last there are very many in various degrees of 

 activity. The most celebrated of these is the Great 

 Geyser. 



