56 



NATURE 



[March 21, 1918 



lithic or aa lava, a " foam-stone," which is expelled 

 in a Mauna Loa flow, cools from within outward by 

 expanding gas suddenly released from solution, and 

 the lava disintegrates into rough units. Lava drawn 



Fig. 2. — Thermal gradient of Kilauea lava lake, temperatures measured with Seger cones, 1917, by 

 T. A. Jaggar. Triangles, circles, crosses, and dots each different series of measurements. 

 A = actual uncorrected readings in large steel pipe. B = corrected gradient of lower lake. 

 C=gradient to crusted lake surface when solidified. — From Journ. Wash. Acad. Sci., July 19, 1^17. 



up from deep within the Kilauea lake tended, on 

 sudden cooling, to effloresce in aphrolithic fashion. An 

 island which ra,pid!y rose from the lake bottom proved 

 to be typical aa or aphrolithic lava. The most satis- 



and spines instead of lava flows. The liquid or dermo- 

 lithic lavas now become products of surface fusion 

 induced by escape of gases from solution in a very 

 stiff intratelluric magma as solvent. A volcano like 

 Kilauea, which among volcanoes 

 exhibits maximum temperatures, 

 probably owes the liquidity of its 

 surface lava to the nature of its 

 gas reactions. 



Cyclical and Sympathetic Lava 



Movements. 

 A complete eruption of Mauna 

 Loa, the summit crater of which 

 is twenty-two miles from the 

 Kilauea sink and about 10,000 ft. 

 higher, consists of a preliminary 

 summit outburst, followed, after 

 months or a few years, by a flank 

 discharge with lava flow. Re- 

 cently the intervals between 

 identical phases of complete erup- 

 tions have averaged something 

 above nine years. Kilauea has 

 shown no hydrostatic response 

 to Mauna Loa lava, hence it 

 was supposed they were un- 

 connected. It will be clear, 

 however, that if a main lava 

 column depends for liquefaction 

 on surface release of gas from a 

 stiff silicate magma solution, 

 hydrostatics plays only a super- 

 ficial rdle, while varying viscosity, differential expan- 

 sion, and tidal stress control relative heights of lava 

 in adjacent and connected conduits of different sizes. 

 During the complete eruptive period of Mauna Loa, 





iia^4s''«^4"" 





U»!l Mas 



MA^LOA 



?,h'. 



Fig. 3. — Diagram showing fluctuatii 

 ments from li 



1 of level of lava in Halemaumau, in relation to seismic and volcanic activities of Mauna Loa, 1914-16. Measure 

 weekly surveys by T. A. Jaggar shown. — Reprinted from Amer. Journ. Sci., April, 1917. 



factory feature of the discovery th^t the Hav^-aiian lava 

 column is probably stiff within the mountain is the 

 correlation now possible with such volcanoes as Pel^e, 

 Bogoslof, or Tarumai, which exhibited hard domes 

 NO. 2525, VOL. lOl] 



1914-16 (Fig. 3), five seismic spasms in that volcano, 

 two of them accompanied by eruption, were responded 

 to in the active lava pit of Kilauea by a series of pro- 

 nounced risings of increasing duration, followed by 



