SPACING OP VOLCANOES 503 



Mamia Loa.^ Hawaii, while not the most recent island, remained active 

 after the others. Kilauea was considered to have originated in the open- 

 ing of a fissure to give exit to the lavas of Manna Loa, but Dana admitted 

 the possibility of overflows having taken place from Kilanea. 



The relative age and the origin of Kilanea and Manna Loa as suggested 

 by Dana was not accepted by Brigham, Dutton, or Green, and later Dana 

 himself reached a different conclusion. Brigham and Grreen suggested 

 a separate origin for these two volcanoes, but Green proposed an entirely 

 new hypothesis for the arrangement of the volcanic centers — that the vol- 

 canoes had arisen at regular distances on three sets of parallel lines, 

 making angles of 60° with each other and spaced 20 miles apart.^ This 

 was the first time that attention was called to the uniform spacing of the 

 volcanoes on the Hawaiian Islands and to the location of the vents at the 

 intersection of fissures as Darwin had noted in the Galapagos. Dutton, 

 before Green, had suggested that Kilauea and Mauna Loa were distinct 

 volcanoes which had grown together,* and that each had originated at the 

 intersection of two entirely different fissure lines. 



After a second visit to the Hawaiian Islands in 1887, Dana stated that 

 the volcanic centers of the group represented "two parallel ranges of 

 islands,^^^ called the Kea Eange on the north and the Loa Eange on the 

 south. Kilauea, according to this scheme, fell into the Kea Eange and 

 was, for this and other reasons, considered to be independent of Mauna 

 Loa and to probably be younger than either Mauna Loa or Mauna Kea. 



Further suggestions regarding the alignment of the vents were made 

 by Alexander and by Woodworth. The former suggested that of the two 

 intersecting fissures at which each vent were formed, one was in the 

 course of the trend of the islands and the other was transverse to this 

 trend. ^ Woodworth compared the arrangement to that of a major ftac- 

 ture system and said : 



"A double line of volcanoes like the Hawaiian does not necessarily imply 

 that there must exist two great parallel fissures in the earth's crust. A single 

 great torsion crack with the attendant fringe of border fractures in the super- 

 ficial layer of the crust, or simple fracturing in accordance with this structure 

 will account for all the phenomena of distribution of volcanoes in couplets 

 along the double line. The commonly accepted view of two parallel fissures 

 fails to account for the occurrence of the volcanoes in couplets and for the 

 interval between them." "^ 



2 U. S. Exploring Expedition, 1838-1842, Geology, pp. 282, 414-416. 



'•^ W. L. Green : Vestiges of a molten globe, vol. 2, Honolulu, 1887. 



* Hawaiian volcanoes, U. S. Geol. Survey, 4tli Ann. Rept, 1882-1883, p. 120 ; Am. 

 Jour. Sci., vol. 25, 1883, pp. 221-226. 



^ Characteristics of volcanoes. New York, 1891, p. 262. 



8 J. M. Alexander : Am. Jour. Sci., vol. 37, 1888, p. 38. 



■^ J. B. Woodworth : On the fracture system of joints, with remarks on certain great 

 fractures. Proc. Boston Soc, Nat. Hist., vol. 27, 1896, p. 182. 



