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KIRK BRYAN 



figure, no attempt has been made to show the comphcated and 

 closely spaced fractures of the upper part of the crust. Only 

 persistent fissures reach the surface, the others merge into the 

 maze of minor fractures and joints. 



Volcanic springs are associated with present or past volcanism. 

 This direct association implies that they have their origin either in 

 water expelled from the underlying magma or in surface water 

 that has come into contact with highly heated rocks and has 

 acquired definite characteristics from this association. In general 

 such springs have strong and relatively constant flows and are highly 



Volcanfc springs Fault spring 



Fissure spring 



Fig. 1. — Diagram illustrating springs due to deep-seated water 



mineralized, and many are gaseous. Some of them have very high 

 temperatures and cannot be sharply divided from volcanic vents 

 emitting steam and gases — fumaroles, solfataras, and mofettes. 

 Others have relatively low temperatures, and many contain 

 carbon dioxide gas. It is generally difficult or impossible to dis- 

 tinguish the latter from springs of non- volcanic origin. The 

 peculiar phenomenon called geyser action characterizes some hot 

 volcanic springs. A typical group of volcanic springs without 

 geyser action lie on the south flank of Lassen Peak, in California 

 (Fig. 2). 



The other group of springs due to deep-seated water may be 

 termed fissure springs. In general they have a strong and constant 



