A THEORY OF BULBOUS BUDDING 



65B 



the incompetence of the strata to sustain the weight of a flow. To apply 

 the term intrusive to the case of a land lava entering water, however, 

 leads to the rather grotesque conception of a surface flow again penetrat- 

 ing the earth and becoming intrusive after having traversed the surface 

 of the land, perhaps for many miles ! 



Platania^'*^ thinks the globular basalt of Acireale, with its mud-filled 

 interstices, "probably due to the injection of magma into a thick stratum 

 of submarine silt." Lawson^** considers the San Francisco pillow basalt 

 intrusive in the accompanying sediments, although Ransome^^^ had for- 

 merly interpreted it as a surface flow on Point Bonita (plate 18, figure 1) 

 and intrusive on Angel Island. Several examples of the structure in 

 Great Britain have been regarded by some authors as probably due to the 

 invasion of soft sediments in process of accumulation by an igneous 

 magma, and Eeuning^*® thinks the splendid Hessian occurrences, where 

 many of the pillows still hang together by narrow necks and in which 

 large masses of sediment are inclosed in places, may have sunk into the 

 slimy ooze of the sea-bottom. 



Platania refers to an experiment by Johnston-Lavis in which a dense 

 viscous liquid on being injected into another assumed spheroidal forms 

 with slight necks connecting them, some of which were severed, leaving 

 the globes detached. Whether this would occur in the conditions under 

 consideration would depend largely, perhaps, on relative density. A very 

 light, insubstantial ooze would probably offer too little resistance to cause 

 the separation of a lava that had not already begun the budding process. 

 On the other hand, it would not interfere with the development and the 

 extension of this process through its mass, and this would give rise to 

 pillow structure in every respect like that which forms on the land or the 

 firm sea-bed, except perhaps in the absence of flat-bottomed pillows at 

 the base of the flow. 



Acknowledgments 



' I am indebted to many members of the Society for assistance in the 

 collection of data for this study. Among these I am under special obli- 

 gations to Dr. Arthur L. Day, Director of the Geophysical Laboratory, 

 for kindly criticism and for the excellent photographs of Kilauea ; to Dr. 



"3 G. Platania : Geological notes of Acireale. The South Italian Volcanoes, ed. bj^ H. J. 

 Johnston-Lavis. Naples, 1891, pp. 37-44. 



1** A. C. Lawson : San Francisco Folio, U. S. Geol. Survey. 



1*5 F. L. Ransome : The eruptive rocks of Point Bonita. Bull. Dept. Geol.. Univ. of 

 Cal., vol. i, 1893, pp. 71-113 ; The geology of Angel Island. Ibid., vol. i, pp. 193-234. 



X46 Ernst Reuning : Diabasgesteine an der Westerwaldbahn Herborn-Dreidorf. Neues 

 Jahrb. Min., etc., B. B., vol. Sxiv, 1907, pp. 390-459. 



