5i8 WHITMAN CROSS 



miles, farther, are, in part at least, known to be remnants of former 

 volcanic piles now reduced by erosion in some cases to mere reefs. 

 So far as I have found statements concerning this long train of islets, 

 they are basaltic, excepting the coral-reef rock. The inference drawn 

 by many geologists who have considered the matter is that all these 

 islands are the products of a long cycle of volcanic eruptions producing 

 similar lavas. It appears to me plausible to assume that the earliest 

 eruptions occurred at or near the western limit of this zone, and that, 

 in a general way at least, the centers of activity have developed suc- 

 cessively farther and farther to the east or southeast, until now the 

 only active loci of eruption are those of Maun a Loa and Kilauea on 

 the island of Hawaii. 



A somewhat different view was taken by J. D. Dana, who has 

 said: 



There is reason for believing that the fires along the Hawaiian line broke out 

 all together at some time in the long past, but only Hawaii has kept on piling 

 up lava streams from that remote time of outbreak until now, and hence has come 

 the altitude of these loftiest volcanic mountains of the Pacific.^ 



Dana recognized, however, that Kauai and Oahu, the most north- 

 westerly of the larger islands, exhibit great erosion. It is also a fact 

 that both these islands are dotted by cinder cones, some of them with 

 craters of model-like form, situated in such independent relation to 

 the topographic forms produced by the great erosion that their later 

 age is unquestionable. 



Whatever the point of first eruption may have been, this volcanic 

 cycle began in a remote geologic epoch, not now determinable, but 

 there are grounds for believing that it may well have been in the 

 early part of the Tertiary period. The chief evidence bearing on 

 this point consists in the destruction of the older centers by enormous 

 and long-continued erosion, the existence of the later tuff cones men- 

 tioned, and the fact that the raised reef of beach deposits abutting 

 against the Diamond Head crater, on the island of Oahu, contain 

 fossils considered by Dr. W. H. Dall to be of late Pliocene or early 

 Pleistocene age. The crater of Diamond Head, however, is but one 

 of many small centers of tuff eruption, belonging to the comparatively 

 recent and feeble epoch of volcanic activity. Oahu may be, more- 

 over, one of the younger islands of the long Hawaiian chain. 



I Characteristics of Volcanoes, pp. 357, 358. 



