54 FOYE. 



Though no embayments are indicated in the outUne of the island, 

 local, pocket-like, marine plains, formed in the process of coastal 

 simplification, occur about the shore of the island and extend an eighth 

 of a mile inland. These plains are often formed of bedded coral and 

 shell rubble occurring 5 to 8 feet above the present sea level and 

 dipping 10° to 12° seaward. 



No definite evidence of the basaltic period of volcanic activity was 

 found in the island. 



General Remarks on the Exploring Group. 



From the study of the several islands lying about the border of the 

 lagoon of the Exploring group, it has been determined: — 



1) That at the first discernible stage of the history, a series of 

 tuffaceous rocks was intruded and covered by andesite, the volcanic 

 terrane being of unknown form and extent; 



2) That, during the erosion of this mass to late maturity, inter- 

 mittent eruption of andesite took place; 



3) That this eroded land was fringed with reefs; 



4) That a period of subsidence followed, leading to the deposition 

 of at least 400 feet of coralliferous limestone unconformably on the 

 volcanic rocks; 



5) That the composite mass was then uplifted, so that the lime- 

 stones are now found 400 feet above sea level ; 



6) That the elevated limestones and andesitic hills were deeply 

 eroded ; 



7) That later basaltic eruptions buried the limestones and ande- 

 sites with ash, agglomerates, and flows; and 



8) That there has been a long period of erosion during which much 

 of the ash and agglomerate of the basaltic period, and much of the 

 limestones, have been swept away. 



The existing isolated islands doubtless did not represent the entire 

 land area previous to the great subsidence. It is probable that a 

 series of rhyolitic and andesitic hills once covered an area at least as 

 large as that enclosed by the present lagoon. It was this surface 

 which was submerged and over which was laid down an unknown 

 amount of Innestone. Most of the islands studied show that their 

 tops were entirely covered by the limestone and it is inferred that at 

 that time a bank of coralliferous limestone marked this portion of the 

 Pacific Ocean. It cannot be stated whether the bank had the form 



