THE BREAKDOWN OF 1891 AS DESCRIBED BY S. E. EILTIOF In the issue of Nature for September 4, 1902, Dr. S. E. Bishop presents his views of the changes in Kilauea in 1892-4: The recent destructive eruption in Martinique has revived interest in the question of the causes of volcanic action. Only lately have I become sensible of the peculiar value of some observations of my own as evidence of the primary force which impels the ascent of lava from its interior habitat, as distin guished from the explosive violence caused by steam generated by the encounter of the ascending lava with ocean and other surface waters.
I have long believed the primary force to reside in the ex pansion of the gases originally occluded in the magma, ever since its first condensation from the nebula. Whenever re leased from solidifying pressure by disturbances of the super incumbent crust, the intensely hot magma bursts into a viscid foam and pushes upwards. In a quiet volcano like our Kilauea, meeting no water to generate explosive steam, the lava wells up continuously and steadily in a comparatively gentle foun tain, which displays effervescence only on the surface.
In support of this opinion I beg to offer positive evidence contained in certain facts observed by myself in Kilauea dur ing April 8-14, 1892, and on August 28, 1894. The volcano had been in very steady and uniform action for nearly two years before the earlier date, and so continued until a short time after the latter date, or nearly five years in all of a quiet, con tinuous and rather copious welling up of lava, wholly unat tended by any explosive action.
On the earlier date I carefully observed the then existing lava-lake during six successive days. This lake occupied the center of the inner crater, called Hale-a-mau-mau, or Fern hut. The main crater called Kilauea is nine miles in circum ference, averaging four hundred feet in depth, and rather un evenly floored with recent lava. Southwest of the center is the inner pit of Hale-a-mau-mau. This pit was at that time nearly circular and 2,400 feet in diameter, with vertical sides averag ing one hundred and fifty feet down to the talus. Before the
welling up of lava began in 189o, the pit had been about 700 feet deep. In two years the lava had risen four hundred feet, and stood within three hundred feet of the rim and main floor.
A lake of liquid lava, covered by a thin, spongy film, occu pied the center of the pit. This lake was nearly circular, averaging 85o feet in diameter. It was bordered by a low dyke, which partially restrained its frequent overflows. Out side the dyke, freshly congealed lava sloped away to the talus. By day the crust-film was grey to the eye, but by night a deep red. It was traversed by numerous fissures of white fire. During the whole time three fountains of lava were welling up with somewhat regular intermittence, and three smaller ones at irregular intervals. There was no explosive action what ever.
The largest fountain was about one hundred and twenty feet southeast of the center of the lake. It played with great regu larity about three times in a minute, rising in a round billow twenty-five feet high and fifty feet in diameter, bursting at the top and falling back to level, its discharge moving in a broad stream towards the center of the lake. The fling of spray from its summit rose to forty or fifty feet above the level.
West of this central fountain were two others of very dif ferent character, being more spasmodic in activity, but never long quiet. Occasionally they would unite their forces for half an hour at a time, forming a stationary line of one hun dred and thirty feet of spraying billow much like a surf-comber with flying spray. This stationary surf-wave was fifteen feet high, incessantly flinging its spray ten feet higher along its whole length. In the night, the effect of these fountains was extremely brilliant and was attended by loud metallic crashing.
The other three fountains were smaller, near the borders of the lake, and often quiet for hours together.