6o6 THE POPULAR SCIENCE MONTHLY 



atoll is built upon a submarine volcanic mountain upheaved from the 

 ocean's floor; but in either case the relation between coral reefs and 

 volcanic peaks is one that possesses a real importance for the zo- 

 ologist. 



The two volcanoes of Savaii and Kilauea occur in island groups that 

 are in every way typical of the so-called " high " islands of the Pacific 

 Ocean. The Samoan Islands, including Savaii, lie almost on a 

 straight line running nearly east and west. Upon examination they 

 prove to be of various ages, for the westernmost, Savaii, bears the active 

 volcano and displays other indications that it is more recent in origin 

 than its neighbor, Upolu; this island, in its turn, is younger than 

 the more rugged Tutuila and Manua to the east. The Hawaiian Is- 

 lands, containing Kilauea, also range with some regularity along a line, 

 which in this case runs west-northwest and east-southeast; but one 

 very interesting difference consists in the fact that the newest island, 

 Hawaii, lies at the eastern end .of the group, while the relative geolog- 

 ical ages of the other islands correspond with their serial geographical 

 order westward to Kauai, the oldest and most sharply sculptured mem- 

 ber of the group. In all other essential respects, the Samoan and 

 Hawaiian Islands are closely similar. Our interest centers about the 

 peculiar features of their two active volcanoes, and the ways in which 

 these agree and differ. 



The new volcano on the island of Savaii is assuredly the more im- 

 pressive of the two. Its total mass is great, but this feature is not so 

 striking as its remarkably rapid development in the short period of 

 five years ; this development and the continual flow of fiery lava from its 

 vast crater entitle it to supreme place in the array of volcanoes now in 

 activity. It lies about eleven miles back from the coast nearly opposite 

 the middle of the north shore of Savaii, which is roughly rhomboidal 

 in outline and forty miles long. Approaching this part of the island 

 by day, the most striking features of the panorama are the two vast 

 clouds of steam that rise from the places where molten lava pours in 

 cascades into the ocean (Fig. 1). Upon the glistening black slopes 

 beyond, jets of vapor mark the vents in the roofs of the tunnels through 

 which the fluid lava runs upon its seaward journey from the crater; 

 and from the crater itself, two thousand feet above sea level, rises a 

 similar fountain of thin steam that quickly merges with the dense 

 clouds above. 



When one looks upon the enormous mass of this new mountain, it 

 seems impossible that five years could be sufficient for its formation, yet 

 this is actually the case. The first crater appeared in August, 1905, 

 upon the floor of a beautiful green valley. As cinders and lava were 

 cast forth, they gradually built up a larger dome and spread out to form 

 the first strata of the great volcanic field. The flow followed the valley 



