Volcano Fact Sheet Dunedin Volcano Description • This long extinct volcano was Dunedin harbour and peninsula are probably around 1000m high but has remnants of the now extinct Dunedin volcano. been eroded down over millions of Lava flow years. The highest point today is Mt It was a shield volcano - a broad volcano that is built up from fluid lava Cargill at 700m. Magma chamber flowing down its gently sloping sides. Features Cause Last eruptive activity • The Dunedin City area, Portobello • These volcanoes occur away from • The rocks are dated at about 10 million Peninsula and Otago Harbour are all part plate boundaries and subduction zones. years ago. of the volcano. They probably arise from hot spots in the Monitoring • The hills surrounding Dunedin (Mt mantle and produce mainly basalt magma. • None is necessary because the volcano Cargill, Flagstaff, Saddle Hill, Signal Hill Eruptive history is extinct. and Harbour Cone) are remnants of the • It began erupting around 16 million volcanic crater. years ago and had 3 main eruptive • The sea has drowned the lower slopes phases. Between phases the slopes of the of the volcano. volcano were forested and traces of these • The area between Port Chalmers and forests are preserved between lava flows Portobello was the vent of the volcano in swamp and lake deposits. and is now part of Otago Harbour. Eruptive material • Outcrops of lava and ash are visible • These are pyroclastic flows, lava flows around the city and harbour. and fall deposits made mainly from basalt magma. Type • This is an extinct shield volcano. www.gns.cri.nz.