Mount Tongariro is a compound volcano in the Taupo Volcanic Zone of the North Island of New Zealand. It is located 20 kilometres (12 mi) to the southwest of Lake Taupo, and is the northernmost of the three active volcanoes that dominate the landscape of the central North Island.
At 11:50 pm (NZST, UTC+12) on 6 August 2012, Mt Tongariro had what was initially believed to be a hydrothermal eruption after a month of increased activity. The eruption occurred at the Te Māri Craters, which had been dormant since 1897.
The eruption occurred in a new vent below the Upper Te Māri crater, and sent blocks as big as 1 metre (3 ft 3 in) in size up to 2 kilometres (1.2 mi) from the vent.
An ash cloud 6.1 kilometres (3.8 mi) high deposited ash into the surrounding area, especially to the east of the volcano. The ash cloud travelled 250 kilometres (160 mi) in four hours. NIWA reported the ash cloud contained about 10,000 cubic metres (350,000 cu ft) of ash, and that the ash cloud was 25 kilometres (16 mi) long and 15 kilometres (9.3 mi) wide 39 minutes after the eruption. Ash and the smell of sulphur was reported in Napier and Hastings.The smell of sulphur was also reported in Wellington, Nelson and Blenheim.