A model for the development of types of atolls and volcanic islands on the Pacific lithospheric plate

Abstract

A literature review on atoll origins and volcanic island development on the Pacific lithospheric plate is combined with bathymetric data on the Hawaiian, Marshall, Caroline, Tuamotu and Society island chains to produce a model which helps explain the development of all major Pacific plate island types. This model incorporates the concept that as new lithosphere is formed along the East Pacific Rise older crust moves north-west towards Asia, cools and causes ocean deepening. Some distance from the East Pacific Rise relatively fixed melting anomalies produce volcanic island chains. In warmer waters these islands develop fringing reefs which continue to grow to wave level as the islands are carried on the cooling plate into deeper water. Raised volcanic island forms can develop on arches produced by the isostatic subsidence of new magmatic outpourings close by. As volcanic islands with fringing reefs move into deeper water almost-atolls and finally true atolls develop. Partly raised and raised forms result if atolls rise over minor upwarps on the crust produced by, 1) asthenospheric bumps, 2) arch flexuring resulting from isostatic subsidence of nearby magmatic outpourings, 3) compression within the lithosphere alongside Pacific plate subduction zones. The model also helps explain certain types of drowned atolls and guyots.