Geology of Rikutsar

Rikutsar is famous for its enormous volcanoes, 4 of which are still visible on the surface. The archipelago formed approximately 11 mya when a mantle plume caused a small flood basalt eruption, creating a tectonic rift northwest of Australia. In the center of the hotspot, a now-submerged volcano began to breach the surface of the young Indian Ocean. The hotspot formed another now-submerged volcano 5 mya and the Swoorlac volcano (responsible for the formation of that island) 1.2 mya.
== Sareanár ==
Of the 4 visible volcanoes, the youngest is Sareanár. It is a shield volcano around 2,000 meters high which formed around 16,000 years ago. Sareanár formed over the Rikutsar hotspot and, despite its flat and spread-out nature, it is by far the most prominent elevation feature of the island. It is the only active volcano on Rikutsar, though multiple older volcanoes dot the archipelago.
At the discovery of Rikutsar in 430 AD, Sareanár was dormant and is thought to have been for centuries beforehand. Activity began again in 506 AD, with small tremors and lava fountains from mountainside fissures. This culminated in a small effusive eruption from the summit caldera and various flank vents on 16 July 510. Other minor eruptions occurred on 1 October 879, 19 February 1320, and 6 May 2011.
== Uźárac ==
The Uźárac caldera lies to the northwest of Sareanár and is an older, dormant stratovolcano. It is thought that the caldera formed approximately 20kya. The only active volcanism seen today at Uźárac are various hot springs and a single geyser, known as Chusore or ”The Gusher.” The current caldera floor lies at an elevation of around 800 meters, and the caldera walls rise a further 300 meters.
== Cazengár ==
The caldera of the Cazengár volcano is the largest caldera on land in the world at 1650.5 km2. It developed to the west of the remnants of older volcanoes 280 kya. Cazengár is responsible for the rocky beaches, crags, and outcrops of Lanul, being remnants of old lava flows. Approximately 67 kya, Cazengár's final eruptions occurred, leaving its lava chamber largely empty. Shortly afterward the volcano collapsed inward and formed a 47 km-long, 35 km-wide caldera. Much of the volcano's long eastern flank fell into the ocean during the collapse. The debris from the landslide accumulated enough to form the island of Pretoac. Afterwards a resurgent dome formed in the center of the caldera, called Oighupre, upon which Cazengár was later built. The formation of the dome marks the last known volcanic activity at Cazengár.
Category:Rikutsar