McDonald Islands (volcano) McDonald Islands (volcano) The McDonald Islands () are the peaks of a volcano in the southern Indian Ocean in the vicinity of Heard Island (). The islands are Australian external territory. Prior to 1992, the volcano had not erupted in the previous 75,000 years. The McDonald Islands volcano comprises three islands: McDonald Island, Flat Island (which later merged with McDonald Island) and Meyer Rock. The islands are mostly composed of phonolitic low-silica pumice, dikes and lava domes, and sit atop a submarine plateau, the Kerguelen plateau. They are located about 75 km from Heard Island. McDonald Island is the largest
Nova Iguaçu Volcano underlain by pyroclastic rock. This rock originated from rock fragments created by a volcanic explosion. The valley is made up of trachyte, another igneous rock with massive texture. The pyroclastic rock was the main justification of the Nova Iguaçu Volcano hypothesis. The existence of a volcano at Nova Iguaçu was proposed by geologists Viktor Carvalho Klein and André Calixto Vieira in the 1980s. Klein and Vieira based their discovery on the presence of pyroclastic rocks (including volcanic bombs) and the existence of a volcanic crater. They believed the pyroclastic rock to be pyroclastic flow deposits, constituting an “extraordinary well-preserved complete