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How were raised coral islands such as Nauru and Banaba formed?

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Map of the Pacific Islands region showing political boundaries, major island groups, and countries such as Papua New Guinea, Fiji, Samoa, French Polynesia, and Kiribati. The map uses color shading to indicate elevation and ocean depth, with key islands and capitals labeled throughout the central and southwestern Pacific Ocean.
Pacific Islands

Raised coral islands, such as Nauru and Banaba, are formed through the process of uplift. Unlike many other Pacific islands that develop through the gradual accumulation of reef debris (accretion), these islands were created when crustal movements raised a previously submarine reef system above sea level.1

Once elevated, these reef tops become low, plateaulike features. Because they are composed of limestone, these islands are subject to subaerial erosion and solution weathering, which sculpts the land surface into rugged, rocky terrain often characterized by cliffs and pitted surfaces. This process of weathering can create a prominent rim and a saucer-shaped interior, sometimes leaving the island with a central basin that may have once been a lagoon.12

While many Pacific islands are explained by the subsidence of volcanic foundations or plate tectonics, raised islands like Nauru and Banaba represent a distinct geological history where tectonic forces have pushed the reef structure upward.314