JOURNAL 



OK THK 



WASHINGTON ACADEMY OF SCIKNCES 



Vol. VII MAY 4, 1917 No. 9 



GEOPHYSICS. — Live aa lava at Kilauea. T. A. Jaggar, Jr., 

 Hawaiian Volcano Observatory. (Communicated by Arthur 

 L. Day.) 



In a paper yet unpublished 1 the writer maintains, from meas- 

 urement and experiment, that the Kilauea lava column is two- 

 fold, a main semisolid incandescent body or "bench magma," 

 filling the Halemaumau pit shaft from side to side for an un- 

 known depth, and a minor shallow liquid lava body or "lake 

 magma," which circulates through several small vertical shafts 

 10 to 30 metres in diameter. These act as conduits and sink- 

 holes below a saucer 8 to 15 metres deep in the bench magma 

 column, this being the well known "lava lake." The lake 

 magma exhibits a convectional circulation, more rapid than 

 that of the bench magma. It builds the bench magma by over- 

 flow and bottom accretion during rising, and uncovers its bottom 

 partially by more rapid subsidence during sinking. The border 

 benches and islands are of crusted protuberant bench magma 

 and are incandescent and mobile within. In the bench magma, 

 under overflooding a,nd its opposite (unloading by the sinking 

 away of the lake), a slow circulation is discernible, which re- 

 sembles isostatic adjustment in its mechanism. 



Under an adjustment of this kind, after subsidence prior to 

 the equinoctial low level of March, 1917, when the lake bottom 

 had been unloaded by a sinking of the lake magma, some 12 



1 Sent to the American Journal of Science. 



241 



