Topic: Taupo Volcanic Zone

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Volcanic activity around Taupo.

Lake Taupo was formed by the massive Oruanui eruption, one of the largest volcanic eruptions in history. The volcanic explosivity index classified that eruption as "apocalyptic", one of only 47 eruptions identified as such. Of these, 42 occurred in the last 36 million years. Oruanui was the most recent, occurring 26,500 years ago.Lake Taupo 

The eruption created a caldera - a depression or void caused when the land caves in following an eruption, essentially a collapsed volcano - which is now filled with the water of Lake Taupo.

The Taupo Volcano roared back into life 1800 years ago, when it erupted again. Although much smaller than the Oruanui eruption, it is still considered the most violent known in the world in the last 5000 years.  The eruption plume reached 50km into the air, well into the stratosphere. All of New Zealand was covered by at least a centimetre of ash, and it's possible that ash from this eruption caused the red sunsets recorded by the Romans and Chinese at the time.

» See how the Taupo Volcano compares to other eruptions

In 2009, Geological and Nuclear Sciences (GNS) volcanologist Dr Gill Jolly said the Taupo volcano was not dormant but "slumbering". Most of the volcano's vents are now under Lake Taupo. It is likely to erupt again, though there is no indication that will be anytime soon.

The Taupo volcano is part of a group of active volcanoes that make up the Taupo Volcanic Zone, a 40km-wide and 240km-long area in the central North Island. It runs from Ruapehu northeast to White Island, off the Bay of Plenty coast, and on towards the Kermadec Islands. Offshore, it takes shape as island and undersea volcanoes. This chain forms part of what's known as the Pacific Ring of Fire, which includes most of the world's 600 active volcanoes.

Other well-known active volcanoes of the Taupo Volcanic Zone include Tongariro, Ngauruhoe and Ruapehu which have shaped the spectacular and dynamic landscape of the Tongariro National Park.

All three volcanoes are stratovolcanoes, which means they are made up of alternating layers of volcanic material that erupted from multiple vents over the last 250,000-300,000 years. Tongariro and Ruapehu are multiple volcanoes, formed from numerous overlapping vents, some young, some old, some active and others dormant. Ruapehu's currently active vent is beneath the crater lake of South Crater, while Tongariro's fumaroles (steam vents) include Ketetahi Springs, Red and Te Maari craters.

Ngauruhoe erupts

Ngauruhoe - famous from its role as Mt Doom in the Lord of the Rings trilogy of movies - is seen as a volcano in its own right, but is technically a secondary cone of Mt Tongariro.

Ngauruhoe's classic cone-shape is typical of young composite volcano. Once the most active volcano of the trio, its last major eruption was in 1975. Early newspapers from the 1800s on frequently reported Ngauruhoe unrest, usually without undue alarm, though larger eruptions did cause some concern. There have been more than 60 eruptions since written records began in 1839, including one in 1926, right.

Tongariro and Ruapehu have both erupted within the last several years, Ruapehu in 2007 and Tongariro in 2012. Ruapehu is the largest active volcano in New Zealand, as well as being the highest peak in the North Island.

The volcanoes of Taupo Volcanic zone are monitored by Geonet, a collaboration between the Earthquake Commission and GNS Science. Both Tongariro and Ruapehu are currently classified as being at Volcanic Alert 1. The alert levels range for 0 to 5 and define the current status of the volcano. Level one means there is minor volcanic unrest.

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Taupo Volcanic Zone

Sources:Williams, K. (2013). Volcanoes of the South Wind: A volcanic guide to Tongariro National Park; Wikipedia; GNS Science;