88 FOYE. 



BEARING OF THE RESULTS OF THE EXPEDITION ON 

 THE CORAL REEF PROBLEM. 



The several theories to account for barrier reefs and atolls are sum- 

 marized, following Davis (1914) in part, by the outline given below. 



I. Theories which do not involve a positive shift of the sea-level. 



A. Atolls built on submerged craters. 



B. Atolls formed by upward growth on still-standing banks. 



1. The banks are graded to the proper level for coral 



growth by the waste from plankton. (^Murray, 1880) 



2. The banks are formed by rapid wave action level- 



ing the scoriatous waste of submarine volcanoes. 

 (Wharton, 1897) 



C. Barrier reefs and atolls formed by progressive outward 

 growth of a fringing reef and the solution of an inner 

 lagoon by ocean water. (Murray, 1880) 



D. Veneering reefs on sea-cut platforms. 



1. Platforms are cut about high, volcanic islands which 



are later reduced to sea-level by subaerial erosion. 

 (Tyerman and Bennet, 1832) 



2. Platforms are cut about elevated masses of corallifer- 



ous limestone. (A. Agassiz, 1899) 

 II. Theories involving a positive shift of the ocean level. 



A. Atolls and barrier reefs built on subsiding islands. 

 (Darwin, 1842) 



B. Atolls and barrier reefs built on platforms cut by Pleisto- 

 cene wave-action and later submerged by the return of 

 Glacial waters to the ocean. (Daly, 1915) 



Murray's theory involving solution by ocean water has been dis- 

 carded by most geologists, because of its quantitative inadequacy. 

 Many writers believe that the banks are antecedent to the veneering 

 reefs since they have greater extent than the reefs (Vaughan, 1914, 

 p. 32), but do not attempt to explain the origin of the bank. In the 

 next few pages the facts gathered in Fiji will be discussed in the light 

 of the above theories. 



While the earliest facts known concerning the two large islands of 

 Viti Levu and Vanua Levu show that they were continental land 

 masses, they were later submerged and covered by volcanic debris. 

 Vanua Levu is composed in large part of submarine volcanic rocks. 



