430 W. T. BRIGHAM ON THE VOLCANIC PHENOMENA 



Periodicity of Eruptions on Hawaii. 



Our knowledge of the Hawaiian volcanoes covers too short a period of their history to 

 determine with any certainty the laws which regulate the discharges. The following table 

 contains all the eruptions that have occurred since the discovery of the Islands : — 



Mauna Loa. Mauna Hualalai. 



1801. 



1832. 

 1843. 



1849 ? Subterranean. 



1858 ? Subterranean. 



ri851.-| 

 Ll852.J 



1855. 



1859. 

 1866. 1866. 



It will be seen that while Kilauea fills up and breaks out in about eight years, Mauna Loa 

 has poured out lava streams at intervals of eleven, eight, three, four, and seven years. The 

 action of Kilauea indicates a constant and regular supply of lava, which accumulates to 

 about the same height and then flows off. In Mauna L5a the action is nearly as regular, if 

 we consider the different elevations from which the discharge takes place. At Kilauea it is 

 always about three thousand feet above the sea, as the reservoir of lava subsides to this 

 level, but on Mauna Loa the discharges have been at thirteen thousand feet or a little below 

 the bottom of the summit crater, nine years after at the same elevation, which afterwards 

 changed to ten thousand feet, thus draining the mountain three thousand feet lower than 

 the last, and requiring three years to fill up to twelve thousand feet, the height of the next 

 outbreak, which continued to flow eighteen months ; four years after at the height of eleven 

 thousand five hundred feet, and finally after seven years of repose, at the height of twelve 

 thousand five hundred feet. 



Usually the eruptions from the several vents have been quite independent, and only twice, 

 in 1832 and 1866, have they been simultaneous. The intervals of neither mountain seem 

 to be increasing, and we learn from native tradition that since the island was peopled by the 

 Hawaiians, some two thousand years since, eruptions have taken place with about the pres- 

 ent frequency at Kilauea. 



Volume of Lava ejected. 



27.000,000,000 cubic feet. 



Exploring Expedition . . 15,400,000,000 " 



These are estimated 1 . 17,000.000,000 " " 



roughly, as the flows [ • . 18,000,000,000 " 



have never been sur- j . 38,096,000,000 " " 



veyed or measured. ! . . 28,560,000,000 " " 



The other eruptions were either subterraneous, or no sufficient data exist for an estimate. 

 The volume of a discharge of Kilauea is probably pretty constant. 



