太平洋プレート
Nauru is positioned in the Nauru Basin of the Pacific Ocean, on a part of the Pacific Plate that formed at a mid oceanic ridge at 132 Ma. From mid Eocene (35 Ma) to Oligocene times a submarine volcano built up over a hotspot, and formed a seamount composed of basalt. The seamount rises over 4300 m above the ocean floor. This hotspot developed simultaneously with a major Pacific Plate reorganisation.