Chapter 16 - Geology and Hydrogeology of the Cook Islands

This chapter describes the geology and hydrology of Cook Islands that are a part of Polynesia. The Cook Islands are located in the central South Pacific between the Society Islands to the east and the Tonga and Samoa Islands to the west. The Islands consist of 15 islands divided into a northern group of six islands and a southern group of nine islands. The population of the Cook Islands has been steadily declining because of dual citizenship with New Zealand and the consequent migration of many to that country. The two groups have distinct climates and oceanographic settings, tectonic origins, geomorphologies, hydrologic resources, and geologic histories. The southern group of islands form two linear volcanic chains; crustal loading and flexure associated with Quaternary volcanism on Rarotonga uplifted the makatea islands. In contrast, most islands of the northern group are located on the tectonically stable Manihiki Plateau, which was formed from an outpouring of lava at a triple junction during the Early Cretaceous.