SOME CAUSES OF VOECANIC ACTIVITY ^ 



By Arthur L. Day 



[With ;5 plates] 



Several years ago I had the privilege of presenting to the Institute 

 some conclusions respecting the sources of the energ}^ through which 

 the lava lake in the crater of the Volcano Kilauea (Hawaii) was 

 maintained in a fluid condition. The evidence then offered was 

 obtained in association with E, S. Shepherd,^ from observations 

 on the ground and in the laboratory, and may be reviewed somewhat 

 briefly as follows : 



Observations of the temperature of the lava lake, taken morning 

 and evening and often at intervening hours of the day and night 

 through a period of two months, revealed very considerable changes 

 of temperature for so large a body of liquid magma. On June 13, 

 1912, for example, the surface temperature was 1,070'^. On July 6, 

 1912, it was 1,185°. Temperatures as low as 950° have since been 

 measured in the lava lake, and in its less active pools any temperature 

 down to the point of actual solidification maj' be encountered. The 

 lake in 1912 had the form of a single pool without partitions, differ- 

 ences of level, or islands, and was approximately 800 feet long by 

 500 feet wide (pi. 1, fig. 1). The depth of course was problematical 

 and not subject to direct observation except that the lava level rose 

 jind fell by small amounts daily and observations over a period of 

 years have shown maximum differences of about 700 feet; the con- 

 taining basin must therefore have had a depth greater than this. In 

 June, 1912, when these temperature observations w-ere made, the lava 

 stood about 200 feet below the rim and therefore some 500 feet above 

 its lowest observed level during those years. The mass of lava con- 

 tained in the basin was therefore very considerable and a rise in its 

 temperature from 1,070° to 1,185°, 115° within 23 days, must in- 

 volve a very large and very rapid access of heat from some source 

 below other than new lava, for the quantity of lava contained in the 

 crater during this 23-day interval under observation w^as substan- 

 tially constant. 



"Address delivered on the occasion of tiie Centenary Celebration of the founding ol' the 

 Franklin Institute, September 17, 18, and 19, 1924. 



2 Arthur L. Day and E. S. Shepherd, Water and Volcanic Activity. Bull. Geol. Soc. Am. 

 24, 573-606, 1913. Smithsonian Annual Report 1913, pp. 275-305. 



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