Geomorphology of oceanic islands

Abstract

Islands can be subdivided into three types: continental, oceanic and those of transit tonal zone. Oceanic islands are presented only by volcanoes and atolls. Erosion and wave action are main exogenous processes modeling volcanic islands. Four factors control the atolls evolution, i. e. coral colonies' growth, fluctuations of the ocean's level, wave action and debris lithification.

Youngest parts of islands are surface of the reef platform, atolls' built-up islands, back parts of beaches and bars, their age being 4000 y. B.P. up to the present. Many of low marine terraces at rising islands are of the Holocene age (2-4 thousands y. B. P.). At tectonically stable islands low terraces date back to Sangamonian or Middle Wisconsin time. High terraces were built during eustatic transgressions. The volcanic islands: came into being 3-2 mln. y. B.P., some of them belonging to the historical time. A general scheme of formation and evolution of oceanic islands is proposed.