F. A. Ferret— Floating Islands of Halemaamau. 273 



Art. XXIII. — The Floating Islands of Halemaumau ; by 

 Frank A. Ferret. 



The view of the crater of Halemaumau — impressive always 

 in its suggestion of potential, if not manifested, power — 

 acquires, at times, a quality of extreme pictnresqueness from 

 the presence of an island, floating tranquilly and apparently 

 unharmed, on the seething bosom of the glowing lava lake. 

 And especially is this the case when, in the course of time and 

 by agencies herein to be described, the rugged mass of rock is 

 softened in its contours and embellished by a graceful line of 

 shore ; whilst a fitfully smoking summit lends a pleasing touch 

 of harmony with an environment so eminently, and so essen- 

 tially, volcanic. Such were the conditions — portrayed in tig. 1 

 — which prevailed during the first weeks of the writer's inves- 

 tigation of Kilauea in the summer of 1911. 



A study of the phenomenon will concern itself with the 

 origin and formation of the islands, their flotation, growth, 

 and the various vicissitudes incident to a more or less ephem- 

 eral existence amid surroundings of the most fervently destruc- 

 tive character. 



The formation of these islands may occur in various ways. 

 It not infrequently happens that, amid the swirling eddies of 

 the surface lava, a certain area — balanced between opposing 

 forces — remains, for a considerable time, at rest. There 

 results the formation of a crust which gradually thickens by 

 accretion from below and may also be built up by overflow 

 movements of the surface material or by the spatterings from 

 some neighboring fountain, until a true island is formed which 

 may move about upon the lake under the influence of a chang- 

 ing surface current. Such islands are not, as a rule, of great 

 mass and are rarely conspicuous while, being composed of 

 comparatively easily fusible materials, their existence is gener- 

 ally a very brief one. 



The formation of a central cone has, at times, been observed 

 at Halemaumau. In 1891 such a cone attained a height of 

 200 feet* and these may be floated upon a rising lava column 

 and be built up through internal ducts. Brigham believes 

 some of the floating islands of Halemaumau to be "incipient 

 central cones, "f and there can be no doubt as to this constitut- 

 ing one of the many processes by which, in this natural amphi- 

 theater where the powers of formation and destruction wage 



*Wm. T. Brigham : " The Volcanoes of Kilauea and Manna Loa," p. 176. 

 Memoirs of the Bishop Museum. Honolulu, 1909. 

 fOp. cit, p. 178. 



