All about Volcanoes - Learn more here
New Zealand is situated on the "Ring of Fire", a geographic belt encircling the Pacific Ocean and containing about 90% of the earth’s volcanoes. Volcanoes usually have short active periods, separated by longer dormant periods. The three main types of volcanoes found in New Zealand are cone volcanoes such as Mounts Ruapehu and Taranaki; volcanic fields such as the ones found in the Auckland area; and calderas such as Lake Taupo.
Volcanoes produce a wide variety of hazards that can harm people and damage property nearby as well as hundreds of kilometres away. Hazards include widespread ashfall, very fast moving mixtures of hot gases and volcanic rock, and massive lahars.
In the Bay of Plenty Region there are four active volcanic centres (active in last 20,000 years); the Okataina Volcanic Centre, Pūtauaki (Mt Edgecumbe), Tuhua (Mayor Island) and Whakaari (White Island). These represent four very different types of hazard to the region.
The Okataina Volcanic Centre
The Okataina Volcanic Centre is a caldera volcano and produces infrequent but large volcanic eruptions. The last eruption was in 1886 and created significant impacts in the BOP region. Moderate to large eruptions usually occur every 700-3000 years and will have a significant impact. The hazard may also present as ‘caldera unrest (see Caldera section below).
Pūtauaki/Mt Edgecumbe is a young, multiple vent complex near Kawerau. The main cone forms the largest part of the complex, erupted as a series of lava flows and volcanic breccias. A lava plug and two small craters occupy the summit. Geological evidence suggests much of the cone has grown in the last 5000 years, with recent eruptions dated around 2300-3100 years ago. No activity is apparent for 1850 years.
Tūhua/Mayor Island lies offshore from the Tauranga-Whangamata area and had a moderate caldera forming eruption about 6300 years ago. Smaller but undated eruptions (500-1000 years old) have followed the caldera forming eruption. Future eruptions will significantly affect the island and may have some impact on the coastal areas.
Whakaari/White Island represents the summit of an active volcanic pile off shore from Whakatane. Typical historic eruptions have no significant impact on the North Island (BOP Region) but can have a significant effect on the island. Pre 1975 historic eruptions were very small and short lived. A sustained eruptive episode occurred between 1975 and 2000 created a new active crater complex and lake. A further eruptive episode started in 2012 and continues.