Short description: Active volcanic zone in New Zealand
Mount NgauruhoeSatellite photo of the Lake Taupo calderaVolcano and lake/caldera locations in the Taupo Volcanic Zone. The distance between the town of Rotorua and the town of Taupo is 80 km. (White Island is not shown.)Whakaari/White Island
The Taupō Volcanic Zone (TVZ) is a volcanic area in the North Island of New Zealand that has been active for the past two million years and is still highly active. Mount Ruapehu marks its south-western end and the zone runs north-eastward through the Taupo and Rotorua areas and offshore into the Bay of Plenty. It is part of the larger Central Volcanic Region that extends further westward through the western Bay of Plenty to the eastern side of the Coromandel Peninsula and has been active for four million years.[1] The Taupo Volcanic Zone is widening east–west at the rate of about 8 mm per year. It is named after Lake Taupo, the flooded caldera of the largest volcano in the zone, the Taupo Volcano.
There are numerous volcanic vents and geothermal fields in the zone, with Mount Ruapehu, Mount Ngauruhoe and White Island erupting most frequently.[2] The zone's largest eruption since the arrival of Europeans was that of Mount Tarawera in 1886, which killed over 100 people. Early Maori would also have been affected by the much larger Kaharoa eruption from Tarawera around 1300 AD.[3]
The last major eruption from Lake Taupō, the Hatepe eruption, occurred in 232 AD. It is believed to have first emptied the lake then followed that feat with a pyroclastic flow that covered about 20,000 km2 (7,700 sq mi) of land with volcanic ash. A total of 120 km3 (29 cu mi) of material is believed to have been ejected, and over 30 km3 (7.2 cu mi) of material is estimated to have been ejected in just a few minutes. The date of this activity was previously thought to be 186 AD as the ash expulsion was thought to be sufficiently large to turn the sky red over Rome and China (as documented in Hou Han Shu), but this has since been disproven.[citation needed]
Taupo erupted an estimated 1,170 km3 (280 cu mi) of material in its Oruanui eruption 26,500 years ago. This was Earth's most recent eruption reaching VEI-8, the highest level on the Volcanic Explosivity Index.
The Rotorua caldera has been dormant longer, with its main eruption occurring about 240,000 years ago, although lava dome extrusion has occurred within the last 25,000 years.[4]
Extent and geological context
The Taupo Volcanic zone is approximately 350 kilometres (217 mi) long by 50 kilometres (31 mi) wide. Mount Ruapehu marks its southwestern end, while White Island is considered its northeastern limit.[5]
It forms a southern portion of the active Lau-Havre-Taupoback-arc basin, which lies behind the Kermadec-Tonga subduction zone.[6][7] Volcanic activity continues to the north-northeast, along the line of the Taupo Volcanic Zone, through several undersea volcanoes (known as Clark, Tangaroa, the Silents and the Rumbles), then shifts eastward to the parallel volcanic arc of the Kermadec Islands and Tonga. Although the back-arc basin continues to propagate to the southwest, with the South Wanganui Basin forming an initial back-arc basin, volcanic activity has not yet begun in this region.[8]
South of Kaikoura the plate boundary changes to a transform boundary with oblique continental collision uplifting the Southern Alps / Kā Tiritiri o te Moana in the South Island. A subduction zone reappears southwest of Fiordland, at the southwestern corner of the South Island, although here the subduction is in the opposite direction. Solander Island is an extinct volcano associated with this subduction zone, and the only one that protrudes above the sea.
Scientific study
Recent scientific work indicates that the Earth's crust below the Taupo Volcanic Zone may be as little as 16 kilometres thick. A film of magma 50 kilometres (30 mi) wide and 160 kilometres (100 mi) long lies 10 kilometres under the surface.[9][10] The geological record indicates that some of the volcanoes in the area erupt infrequently but have large, violent and destructive eruptions when they do. There is also some possible rifting in the Taupo Volcanic Zone.
In 1886, Mount Tarawera produced New Zealand's largest historic eruption
Okataina Volcanic Center: The Haroharo and Tarawera complexes impounded the lakes against the outer margins of the Okataina Caldera. The Okareka Embayment and the Tarawera Volcanic Complex are inside the Haroharo Caldera which in turn is inside the Okataina Ring Structure, from Newhall (1988),[14] but newer maps show Okataina smaller.
Lady Knox Geyser, Waiotapu geothermal areaCraters of the Moon geothermal area
Maroa Volcanic Center: The Maroa Caldera formed in the Northeast corner of the Whakamaru Caldera, the Whakamaru Caldera partially overlaps with the Taupo Caldera on the South. The Waikato River course follows roughly the northern Maroa caldera rim on one side. The town of Whakamaru and the artificial Lake Whakamaru, on the Waikato River, have the same name too.[13]
Composite satellite image of Mount RuapehuSatellite view of the Lake Rotorua Caldera. Mount Tarawera is in the lower right corner.Southwest side of Mount Tarawera, Mount Edgecumbe on the background.
Tongariro Volcanic Center: Lake Taupo, Kakaramea, Pihanga, Tongariro and Ruapehu are roughly aligned on the main fault.
Other important features of the TVZ include the Whakatane, Ngakuru and Ruapehu grabens.
Note
There is nowadays a somewhat different classification:[19][20]
North part: Whakatane Graben – Bay of Plenty
Central part:
West of the main fault zone:
Mangakino caldera complex; may be transitional between Coromandel Volcanic Zone (CVZ) and Taupo Volcanic Zone (TVZ) (1.62 – 0.91 mio. years old)
Kapenga caldera; lies between the Maroa caldera and the Rotorua caldera, it is completely buried under more recent tephra (circa 700,000 years old)
Okareka Embayment, lies inside the northern end of the Kapenga Caldera, between the Tarawera volcanic complex and the Lake Rotorua[17]
Rotorua single event caldera; Mamaku Ignimbrite (circa 240,000 years old)
Main fault zone:
Okataina caldera complex
Haroharo caldera complex
Tarawera volcanic complex
Okareka Embayment
Whakamaru caldera complex
Maroa caldera
Ohakuri single event caldera; Ohakuri Ignimbrite; lies West of the Ohakuri Dam, the Waikato River course follows roughly the southern caldera rim on one side (circa 240,000 years old).[21]
Taupo caldera complex
East of the main fault zone:
Reporoa single event caldera; Kaingaroa Ignimbrite (circa 240,000 years old)
↑Cole, J.W.; Darby, D.J.; Stern, T.A. (1995). "Taupo Volcanic Zone and Central Volcanic Region: Backarc Structures of North Island, New Zealand". in Taylor, Brian. Backarc Basins: Tectonics and Magmatism. New York: Plenum. p. 3. ISBN978-1-4615-1843-3.
↑Parson, L. M.; Wright, I. C. (1996). "The Lau-Havre-Taupo back-arc basin: A southward-propagating, multi-stage evolution from rifting to spreading". Tectonophysics263 (1–4): 1–22. doi:10.1016/S0040-1951(96)00029-7. Bibcode: 1996Tectp.263....1P.
↑Villamor, P.; Berryman, K. R. (2006). "Evolution of the southern termination of the Taupo Rift, New Zealand". New Zealand Journal of Geology and Geophysics49: 23–37. doi:10.1080/00288306.2006.9515145.
↑Cole, J.W. (1990). "Structural control and origin of volcanism in the Taupo volcanic zone, New Zealand". Bulletin of Volcanology52 (6): 445–459. doi:10.1007/BF00268925. Bibcode: 1990BVol...52..445C.
↑Krippner, Stephen J. P.; Briggs, Roger M.; Wilson, Colin J. N.; Cole, James W. (1998). "Petrography and geochemistry of lithic fragments in ignimbrites from the Mangakino Volcanic Centre: implications for the composition of the subvolcanic crust in western Taupo Volcanic Zone, New Zealand". New Zealand Journal of Geology and Geophysics41 (2): 187–199. doi:10.1080/00288306.1998.9514803.