198 Jaggar — Yolcanologic Investigations at Kilauea. 



It lias been stated above that some fountains do not burst 

 through the surface, but merely heave it in a sudden abortive 

 effort without breaking the crust or emitting gas. These in- 

 dicate that explosion takes place below the surface with such 

 balance of reactions that the gas product replaces the re-agent 

 gases. There is no evident ballooning over them, the crust is 

 simply heaved suddenly and sinks back and the gas produced 

 is disseminated below\ 



There is no evidence from artilicial stirring of the surface 

 that a condition of general tension exists immediately under 

 the surface crusts. Stirring with an iron pipe does not generate 



Fig. 18. 



Fig. 18. Mar. 10, 1916, 6 p. m. Night view upper surface lava column 

 Halemaumau from S., rising and overflowing lake, strong activity, depres- 

 sion 450 ft. (137 m.). Dimensions and conditions extraordinarily like 

 those of six months before (Pi. la, upper view), though a marked subsidence of 

 lava column had intervened. Western conduit pond on left crusted over and 

 dark, middle region moderate luminosity and fountaining, maximum oxida- 

 tion shown on the right by flaming, sinkhole fountaining, breaking up of 

 crusts, and fuming. The luminous line on the extreme right is a cascade 

 rivulet pouring down from the lake among tumbled crags. Photo Jaggar. 



a fountain. A fall of rock tumble into the lake carries down 

 great quantities of air in vesicles, and fountaining immediately 

 results. A log of wood thrown into the lake end on remains 

 below the crust, carbonizes, produces jets of red flame and in- 

 duces fountaining. In both of these last cases reaction between 

 the hot gas of the magma and an oxidizing agent is responsible 

 for fountaining. 



Mechanism of Different Types of Fountains. 



With great quantities of air-tilled crust ceaselessly founder- 

 ing in a gas-charged melt cooler than their fusing point, the 



