284 J. D. Dana — History of the Changes in Kilauea. 



lifts of the floor, large enough to act somewhat equably against 

 the floor. Thirdly, since the floor kept its even surface as it 

 fell at the great eruption of 1840, it must have followed down, 

 as already urged, the subsiding lavas (page 213). The flotation 

 method, or that by direct thrust, seems therefore to be the right 

 one. It is the obvious explanation of the lifting of the debris 

 cones of Halema'uma'u. 



Kilauea affords, as has been indicated, facts illustrating the 

 details connected with the lifting movement. 



3. Fault planes of the up-and-down movements about the pit. 

 — (1) The down-plunge of 1823, 1832, and 1S40 left, for the 

 most part, vertical walls bounding the " lower pit " so made. 

 There is evidence that these were fault-walls, that is, planes of 

 fracture with a vertical displacement along them equal to their 

 height, or about 400 feet in 1840 and 600 or 800 feet in 1823. 

 In the reverse movement, that is, the rise after the down-plunge 

 of 1840, the old floor was carried up along the same fault-planes. 

 The rate of rise, as shown on page 16, was 70 to 130 feet a 

 year, which is to be divided between (a) overflows (5), vesicula- 

 tion if this had any effect, and (c) ascensive force apart from 

 vesiculation. 



Further: these vertical fault -planes of 1840, and others 

 subordinate to them along the border regions, appear to have 

 determined the chief places of eruption, that is, of lava-lakes, 

 cones, ovens and opened fissures in Kilauea during the next 

 thirty years. They were plainly the occasion of the wonderful 

 girt of fires, four miles long and half a mile wide, which was 

 three times repeated after the year 1846 before the eruption of 

 1868 (in 1855, 1863, and 1866), while the interior plateau 

 suffered relatively little change from erupting forces, and in 

 some parts was growing ohelo bushes and ferns. 



The position of the " canal" in Kilauea in 1846 described by 

 Mr. Lyman and also by Mr. Coan, as extending around the 

 crater, bounded by the outline of the old black ledge and the 

 Lyman ridge of lava-blocks, and which became gradually 

 filled by inflowing lavas and debris, has here its explanation. 

 The circumferential fault-planes of the pit of 1840 coincided 

 with the face of the lower wall or precipice. The debris 

 which fell from the wall necessarily fell to the floor beyond the 

 plane and there began the making of the talus. Through the 

 fall of the face of the wall, the wall, and thereby the limit of 

 the black ledges, retreated, ahd as the elevation of the floor 

 went on, an interval was left between the talus and the limit 

 of the black ledge, and along this interval lay the "canal/"' 

 The annexed figure will serve to illustrate the point, notwith- 

 standing the assumptions made in it. Let W be the wall of 

 the lower pit, 400 feet high, and the course of the fault- plane ; 



