Haroharo Caldera

The Haroharo Caldera (Haroharo volcanic complex) is a 26 by 16 km (16.2 by 9.9 mi) postulated volcanic feature in Taupō Volcanic Zone of the North Island, New Zealand within the larger and older Ōkataina Caldera. Since 2010 further studies have tended to use the terms Haroharo vent alignment, Utu Caldera, Matahina Caldera, Rotoiti Caldera and a postulated Kawerau Caldera to the features assigned to it.[1] However the name is used in the peer reviewed literature to summarise and group these features based on gravitational and magnetic features.[2]: 14 

Main article: Ōkataina Caldera

Geography

In the north the Haroharo Caldera has been mapped as extending from the eastern half of Lake Rotoiti to the western border of Lake Rotoma. Its southern extent was defined by the Tarawera volcano. A recent analysis is consistent with the south western structural boundary of the older single event caldera's being in the eastern portions of Lake Tarawera.[2] Both the Okareka Embayment and the Tarawera Volcanic Complex are adjacent, so many, especially older maps, had these features overlapping the Haroharo Caldera or Okataina caldera as part of the Haroharo volcanic complex or Ōkataina volcanic centre.[3]

Geology
Okataina Volcanic Centre relationships to other nearby volcanic and tectonic structures
Okataina Volcanic Centre (approximate thick white border) relationships to other nearby volcanic and tectonic structures. The Haroharo Caldera was contained within and extends from its north to south

The Haroharo Caldera was within the older and larger Ōkataina Caldera and its boundaries in geological terms are related mainly to the Matahina and Rotoiti sub-calderas which were formed in single eruption sequences.[1] These boundaries relate to events that happened before about 45,000 years ago.[2]: 2  It is therefore not regarded now as a caldera in its own right formed by one single event and there have been many attempts to rationalise the literature from a descriptor used since at least 1962.[lower-alpha 1] There have been multiple significant eruptions from the Haroharo vent line, that is parallel and to the north of the Mount Tarawera vent line and also within the Ōkataina Caldera. There has been a large amount of dome infilling that refer to the Haroharo name, but the term Ōkataina complex volcano is felt by many to be a better name than the Haroharo volcano to understand the processes that have happened in this portion of the Taupō Volcanic Zone.[4]

Within the Haroharo vent line there was a VEI-5 volcanic eruption about 6060 BCE producing about 17 km3 (4.1 cu mi) of eruptive material and one about 2000 years later that produced 13 km3 (3.1 cu mi) of material.[5] With its linear parallel young vent alignment to those of the similarly young in geological terms, Tarawera volcano, and related magma sources, this means it is now usually regarded as a subsidiary volcanic part of the Ōkataina Caldera which in the last 21,000 years has contributed a total magma eruptive volume greater than about 80 km3 (19 cu mi).[6][7]


Notes
  1. The following is recorded in the geology literature:
    HaroHaro pile ... are rhyolite lavas of the Okataina Volcanic Centre, extruded on the floor of Haroharo Caldera
    — J. Healy, Geology of the Rotoroa District 1962, p54-55
    with the author presuming that certain ignimbrites came from this source.

References
  1. Hughes, Ery C.; Law, Sally; Kilgour, Geoff; Blundy, Jon D.; Mader, Heidy M. (2023). "Storage, evolution, and mixing in basaltic eruptions from around the Okataina Volcanic Centre, Taupō Volcanic Zone, Aotearoa New Zealand". Journal of Volcanology and Geothermal Research. 434 (107715). doi:10.1016/j.jvolgeores.2022.107715. ISSN 0377-0273.
  2. Caratori Tontini, F; de Ronde, CEJ; Black, J; Stucker, VK; Walker, SL (2023). "The geology and geophysics of Lake Tarawera, New Zealand: Implications for sublacustrine geothermal activity". Journal of Volcanology and Geothermal Research. 433. doi:10.1016/j.jvolgeores.2022.107731. ISSN 0377-0273.
  3. Newhall, Christopher G.; Dzurisin, Daniel (1988). "Historical unrest at large calderas of the world". USGS Bulletin. 1855: 1108. Citing Scott, B.J. (1986). Gregory, J.G.; Watters, W.A. (eds.). "Volcanic hazards assessment in New Zealand: Monitoring at Okataina Volcanic Centre". New Zealand Geol. Surv. Rec. 10: 49–54.
  4. Spinks, Karl D. (2005). "Rift Architecture and Caldera Volcanism in the Taupo Volcanic Zone, New Zealand".
  5. Hodgson, K. A.; Nairn, I. A. (August 2004). "The Sedimentation and Drainage History of Haroharo Caldera and The Tarawera River System, Taupo Volcanic Zone, New Zealand" (PDF). Operations Publication 2004/03. Environment Bay of Plenty: 7. ISSN 1176-5550. Archived from the original (PDF) on 2010-05-22.
  6. Smith, Victoria; Shane, Phil; Nairn, I.A.; Williams, Catherine (2006-07-01). "Geochemistry and magmatic properties of eruption episodes from Haroharo linear vent zone, Okataina Volcanic Centre, New Zealand during the last 10 kyr". Bulletin of Volcanology. 69 (1): 57–88. doi:10.1007/s00445-006-0056-7.
  7. Cole, J. W.; Spinks, K. D. (2009). "Caldera volcanism and rift structure in the Taupo Volcanic Zone, New Zealand". Special Publications. London: Geological Society. 327 (1): 9–29. Bibcode:2009GSLSP.327....9C. doi:10.1144/SP327.2. S2CID 131562598.
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