Easter Island lies atop the Rano Kau Ridge, and consists of three shield volcanoes with parallel geologic histories. Poike and Rano Kau exist on the east and south slopes of Terevaka, respectively. Rano Kau developed between 0.78 and 0.46 Ma from tholeiitic to alkalic basalts. This volcano possesses a clearly defined summit caldera. Benmoreitic lavas extruded about the rim from 0.35 to 0.34 Ma. Finally, between 0.24 and 0.11 Ma, a fissure developed along a NE-SW trend, forming monogenetic vents and rhyolitic intrusions. These include the cryptodome islets of Motu Nui and Motu Iti, the islet of Motu Kao Kao, the sheet intrusion of Te Kari Kari, the perlitic obsidian Te Manavai dome and the Maunga Orito dome.