JOURNAL 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. VII JULY 19, 1917 No. 13 



GEOPHYSICS. — Thermal gradient of Kilauea Lava Lake. T. A. 

 Jaggar, Jr., Hawaiian Volcano Observatory. 



Experimental temperature measurement with Seger cones in 

 steel pipes thrust into the lava and flaming cones in 1917, when 

 the lava pool of Halemaumau became accessible, yielded results 

 of increasing accuracy as the method was improved and the 

 sources of error or failure were discovered and eliminated. 



The temperature of the fountains and grottoes, where gas 

 effervescence induces ebullient doming, flaming, and spraying 

 of incandescent melt, is now well known. 1 Excessive oxida- 

 tion of the combustible constituents S, CO, and H on contact 

 with air makes the confined and continuously flaring grottoes 

 hotter than the central fountains. The temperatures vary, 

 but 1130°C. for the fountains and 1180° for the open grottoes 

 (fig. 1, circles) are recorded measurements approaching the 

 maximum. Measurements in the past have been made with 

 Fery 2 and Holborn-Kurlbaum optical pyrometers and with the 

 platinum-rhodium element, and have shown that the surface 

 temperatures of the Kilauea magma range from 940° to 1185°. 

 Temperature measurement below the surface, or in the gas-filled 

 chambers and orifices of flaming blowing-cones on the benches, 

 has not been attempted before this year. 



1 Report Hawn. Volcano Observatory, Boston, January-March, 1912, p. 51, 

 Bui. Geol. Soc. Amer., 24: 601. 1913. Am. Journ. Sci., 36: 151. 1913, 



2 Proc. Am, Acad, Arts and Sci., 47: No. 3. 1911. 



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