350 "ALBATEOSS" TEOPICAL PACIFIC EXPEDITION. 



Andema Islands. 



Plates 183, fig. 4.; 183, fig. 1 ; 225, 230. 



Andema^ atoll is irregularly triangular in shape, with sides of about 

 seven miles in length. It is about eight miles to the west of Ponapi 

 (PI. 230). The islands composing the atoll of Andema are all low 

 (PL 182, fig. 4), flanked by coarse shingle beaches, with but few coral 

 blocks on the outer edge of the narrow reef flat. A ship passage 

 from sixteen to twenty fathoms deep opens into Andema lagoon. The 

 gap between the island of Kahalape and Pachiai has been formed by 

 the same process as have the gaps of the Marshall Islands. Coming from 

 the southeast, we see that the northern island on the east face (PI. 183, 

 fig. 1), and those on the southern face of the atoll, are flanked by low 

 shingle beaches ; the land rim is limited to the southeastern and eastern 

 faces. On the northern and western sides the reef flat is bare, with a 

 few narrow ledges, and comparatively few heads of coral are exposed at 

 high water (PI. 230). 



The islands of the land rim of Andema, like those of Pingelap, have 

 been thrown up on an undei'lying base, probably a volcanic summit 

 planed down, as were probably a number of the other low atolls of 

 the Carolines. On Panemur, the westernmost island of the group (PI. 

 230), large coral boulders form the outer edge of the reef flat, with 

 here and there a few fragments of volcanic i^ocks, showing that the 

 land rim of Andema must at one time have consisted, in part, of vol- 

 canic rocks. It is difficult to explain the formation of such islands as 

 Andema and Pingelap and similar low atolls in the Carolines as due to 

 subsidence. We can trace in Pingelap, Truk, Kusaie, and in Ponapi 

 four successive stages of disintegration, due to denudation and erosion, 

 of which Ponapi is the highest, Kusaie the next, and Truk still lower, 

 imtil we reach such submarine platforms as those of Andema and of 

 Pingelap. If we ascribe their formation to subsidence, we must admit 



1 H. O. Chart 425. 



