in the Summer of 1911. 



473 



sank below its shore, as shown in fig. 2, leaving a pit which, it 

 is interesting to remember, stood within the pit walls of the 

 black ledge; this, in turn 

 Halemauman, which, itself 



thus forming a series of four pit-like depressions, one within 

 the other. But the shore — undercut and plastic in its founda- 

 tions — soon yielded to gravity as the support of the lava 

 column was withdrawn, and settled with a downward inclina- 



being encircled by the walls of 

 ies within the great Kilaaea basin, 



Fig. 2. 



Fig. 2. The lava sinking in the central pit. 

 in background. 



Debris of falling walls seen 



tion toward the edge of the lake, as depicted in iig. 3, where- 

 upon the unsupported black ledge began to give way in a 

 series of majestic downfalls, the impressiveness of which cannot 

 be adequately described. Although on a smaller scale, the 

 collapse of these previous formations was comparable to that 

 of Vesuvius after the eruption of 1906." At the west and 

 north sides the rock of the wall was under a powerful stress 

 and detachment was accompanied by a sharp report as, with a 

 crashing roar, the avalanche of broken rock descended in a 

 cloud of stony dust (fig. 4) to form the talus, which finally 

 extended to the edge of the lake, as may be seen in fig. 3. 



* Frank A. Perret : " Vesuvius : Characteristics and Phenomena of the 

 present Repose Period," this Journal, November, 1909. 



