Gilbert and Ellice Islands atolls and coral islands in the western Pacific Ocean that are recognised as part of the Micronesia subregion of Oceania. The Gilbert Islands are the main part of what is now Republic of Kiribati ("Kiribati" is the Gilbertese rendition of "Gilberts") The atolls and islands of the Gilbert Islands are arranged in an approximate north-to-south line. In a geographical sense, the equator serves as the dividing line between the northern Gilbert Islands and the southern Gilbert Islands. The Ellice Islands are south of the Gilbert Islands. The Ellice Islands comprises three reef islands and six true atolls spread out between
Geology of the Pacific Ocean Plate in the north, the Cocos Plate off today's Central America, and the Nazca and Phoenix Plates in the southern Pacific. Charles Darwin had proposed a theory of the slow subsidence of the ocean floor based on his studies of Pacific oceanic islands, seamounts (underwater volcanoes) and guyots (flat-topped seamounts). His observations have been verified and expanded in the development of plate tectonic theory. The tectonic plates continue to move today. The slowest ridge spreading rate is across the Gakkel Ridge in the Arctic Ocean which separates at less than 2.5 cm/yr while the fastest, across the East Pacific Rise