BY H. I. JENSEN. 643 



formed in the first place by a gigantic fissure eruption, and that 

 on the closing of the fissure and diminution of volcanic energy 

 lava continued to be exuded at a number of points along the 

 original fissure. 



Some of the craters contain beautiful crater lakes like Lanutoo 

 in Upolo, and Mt. Pule in Savaii. Lanutoo crater lake, which 

 I visited, has no outlet, and yet the water in it always keeps the 

 same level. This peculiarity seems to be due to the fact that the 

 walls of the crater are composed of alternating lava streams and 

 porous tuff beds. The lake is supplied by a copious rainfall, and 

 is drained through the porous tuffs of its wall. Other craters 

 have no lakes. These usually consist essentially of porous rock 

 (e.g. Tofoa in Upolo). 



The height of the range which forms the backbone of Upolo 

 exceeds 2000 feet, and many of the peaks on it surpass 3000 feet 

 in altitude. From the craters, long ridges representing lava 

 flows descend to the sea. Their slope is generally speaking 

 gentle, usually ranging between 5 and 10 degrees. Although 

 the craters of Upolo show no activity, the lava is in many places 

 so fresh that it is probable that several of the craters have been 

 active within the last thousand years. The rock is everywhere 

 the same, consisting of more or less vesicular basalt, usually 

 olivine-bearing and varying in crystallinity from hemicrystalline 

 to glassy. 



Savaii is a somewhat dome-shaped island. It is studded with 

 craters, the largest and most important of which lie on the back- 

 bone of the island. The highest peaks are probably not much 

 short of 6000 feet high, and 4500 feet is the average height of 

 the middle of the main range, which, however, diminishes in 

 altitude to the east and west. Arched lava streams are seen in 

 all parts. They run from the central mountains to the sea. 

 Only the craters in the interior have given rise to much lava. 

 Other cones with craters exist; but they are of a comparatively 

 small size, and they are situated on cross fissures which radiate 

 from the interior of the island. The lava is very uniform in 

 composition, but varies considerably in texture and appearance. 



