Ōkataina Caldera

Ōkataina Caldera (Ōkataina Volcanic Centre, also spelled Okataina) is a massive, recently active volcanic caldera and its associated volcanoes located in Taupō Volcanic Zone of New Zealand's North Island. It is just east of the smaller Rotorua Caldera and southwest of the much smaller Rotomā Embayment which is usually regarded as an associated volcano. It is best known for its high rates of explosive rhyolitic volcanism although its last eruption was basaltic. Confusingly the postulated Haroharo Caldera contained within it, has sometimes been described in almost interchangeable terms with the Ōkataina Caldera or volcanic complex or centre and by other authors as a separate complex. Since 2010 other terms such as the Haroharo vent alignment, Utu Caldera, Matahina Caldera, Rotoiti Caldera and a postulated Kawerau Caldera have replaced this classification.[2]

Ōkataina Caldera
Ōkataina Volcanic Centre, Okataina Caldera, Okataina Volcanic Centre
Okataina Volcanic Centre relationships to other nearby volcanic and tectonic structures
Highest point
Coordinates38°10′S 176°30′E
Dimensions
Length28 km (17 mi)[1]
Width15 km (9.3 mi)[1]
Geography
Ōkataina Caldera is located in New Zealand
Ōkataina Caldera
Ōkataina Caldera
Ōkataina Caldera is located in North Island
Ōkataina Caldera
Ōkataina Caldera
Ōkataina Caldera (North Island)
CountryNew Zealand
RegionBay of Plenty
Geology
Age of rock
Mountain typeCaldera
Volcanic regionTaupō Volcanic Zone
Last eruption1886 Tarawera, 1973 Hydrothermal in Waimangu Volcanic Rift Valley
Climbing
AccessState Highway 5 (New Zealand)
The 1886 eruption of Mount Tarawera, as depicted in this contemporary painting by Charles Blomfield, is the most recent major eruption from the Ōkataina Caldera.

Geography

The caldera covers an area of about 450 square kilometres (170 sq mi), stretching from Lake Rotoehu in the north to Lake Rotomahana in the south.[3] The north east boundary bisects Lake Rotoiti and the north east includes all of Lake Rotomā. The south west corner is defined by the domes of the Ōkareka Embayment and the Waimangu Volcanic Rift Valley while the south east aspect is dominated by Mount Tarawera and the volcanic badlands of the Puhipuhi Basin. The caldera also contains several lakes, including part or all of Lake Ōkareka, Lake Ōkataina, Lake Rotoehu, Lake Rotomā, Lake Rotoiti, Lake Rotomahana, Lake Tarawera and Lake Tikitapu.[3]

Geology

The overwhelming volcanic deposits are rhyolite, with some basalt and one area of dacite. The caldera is now thought to contain the Utu Caldera, the major event Matahina Caldera, the Rotoiti Caldera, and the Kawerau Caldera with three associated geologically collapse structure embayments.[2] These are Rotomā Embayment, historically regarded as a caldera, the Ōkareka Embayment as another, now in-filled caldera and the Puhipuhi Embayment. The oldest parts of the caldera basement are now over 5 km (3.1 mi) deep and the younger Rotoiti and Kawerau calderas are still 2.5 km (1.6 mi) deep and largely infilled by eruptives.[2]

Eruptions

The caldera has seen six eruptions in the past 10,000 years, most recently the 1886 Mount Tarawera eruption in the caldera's southeastern corner. The caldera contains two major lava dome complexes, the Haroharo vent alignment in the north and Tarawera vent alignment in the south. Other volcanoes connected with the caldera include Putauaki (Mount Edgecumbe) [4] and the maar crater of Lake Rotokawau which is most likely to have formed from a basaltic dike extrusion associated with the common magma mush body.[5]

Threat

While most currently active New Zealand volcanoes produce small eruptions relatively frequently, Ōkataina's volcanoes tend to erupt very violently after intervals of centuries. As such, they pose significant potential threats to the Bay of Plenty Region but are also the most significant volcanic risk in New Zealand.[4] During the last 20,000 years, pyroclastic and lava eruptions have occurred of several types; low-silicate basalt eruptions, high-silicate rhyolite eruptions, and the rarer intermediate andesite and dacite eruptions. The most common magma type at Ōkataina is rhyolite.[4] The warning time before eruptions is currently suspected to be potentially hours as volcanic unrest signals are very non specific, historic composition analysis is consistent with this speed from magma reservoir to surface and this was all the warning given by the only rhyolitic eruption of the modern era.[6]

How and Why

The reason for the various types relate to the underlying arc volcanism, which is driven initially by large inputs of basaltic melt (from in this case the subducted Pacific Plate). These basaltic melts often never reach the surface due to a relatively high density of the magma compared to the surrounding Australian Plate crust. An example of dyke intrusion that never reached the surface, was manifest as an earthquake swarm during a recent period of volcanic unrest.[7] Usually, these intrusions cool in the crust and either solidify to gabbroic plutons or are associated with the generation of more evolved magmas with higher silicate content that separate and ascend to then erupt as rhyolite, dacite, or andesite, possibly primed by a basaltic melt predecessor. These evolved intrusions can also cool without erupting to form a felsic pluton. In the case of the Ōkataina Caldera the sub-surface architecture is known to be made up of discrete rhyolitic melt-mush pockets that erupt compositionally distinct magmas within single eruptions. The mush pockets are not usually andesitic but in a region towards the east of the Caldera, in the Puhipuhi Embayment, have been dacitic.[7] Little is known of the evolution of the primary basaltic magmas that generate these more evolved rhyolitic magmas and they may not be the same basaltic melts that sometimes cause the final eruption for all that is known. Heat and volatiles are assumed to be transferred between basalts and rhyolites. Basaltic-rhyolitic magma interaction definitely happens (the evidence is in the science of compositional analysis done world wide), and will be a factor in the many different eruption styles that have occurred. Sometimes basalt appears to lead the eruption, at other times it has been postulated that tectonic earthquakes are the final enabler of an eruption.[2][8]

Any basaltic magmas that do reach the surface will have traversed this complicated crustal region and often erupt as a dyke. This must have happened with the 1886 Mount Tarawera eruption which was basaltic and so the initiating magma melt source during its rise to the surface did not transverse a region with more evolved magma melt.[2] In the context that there is evidence for a magma reservoir under the caldera, the absence of a more evolved magma from the 1886 eruptives might have been because it was too soon after the last eruption for such evolution to have occurred, the basaltic melt angled in missing a pre existing more evolved melt or that the evolved melt was solid when transversed.[2] The common very explosive nature of any secondary rhyolite eruptions after this basaltic melt priming is related to rhyolite's viscosity, further complicated by its accumulation time as it is less able to find its way to the surface compared to say the more fluid andesite.[2]

History

It is likely that the volcanic history of the area began some 625,000 years ago.[9] The caldera was formed by at least five huge eruptions between 400,000 and 50,000 years ago, causing the collapse of the ground. The oldest as characterised by gravity and magnetic studies of these sub caldera has been called the Utu caldera in the center south and has now a basement about 5 km (3.1 mi) below present ground level.[2] The most significant collapse event with an eruptive volume of 150 cubic kilometres (36 cu mi) was 280,000 years ago[10] and associated with eruption of the Matahina Ignimbrite which covers over 2,000 km2 (770 sq mi).[1] This second major phase Matahina caldera is to the south east and has similarly abasement about 5 km (3.1 mi) below present ground level.[2] The shape of the Matahina caldera was then modified (and buried/destroyed) by eight smaller eruptions and other processes which occurred between 70,000 and 24,000 years ago. For example the dacite Puripuri basin/embayment is a subsidence related feature related to lateral magma migration towards the eastern caldera margins of mainly the Matahina caldera.[2] The paired approxiamately 50,000 years ago[11] Rotoiti eruption and Earthquake Flat eruption at far ends of the caldera had eruptive volumes of 120 cubic kilometres (29 cu mi) and 10 cubic kilometres (2.4 cu mi) respectively.[1] The Rotoiti caldera is to the north of the Utu caldera.[2] Between this eruption and 21,000 years ago over 81 km3 (19 cu mi) of Mangaone silicic plinian tephras or pyroclastic flow deposits occurred but eruptive centres can not be assigned. However one of these events can be assigned to the Kawerau Ignimbrite eruption of 33,000 years ago as a location within the central part of the Matahina Caldera at level of the Puhipuhi Basin. [1] Gravimetric studies are consistent with the Kawerau Caldera being here as a fourth phase of the true caldera eruptions and with basement about 2 km (1.2 mi) below present ground level.[2] Although the latest caldera models include the Haroharo vent alignment they do not include the existence of a Haroharo caldera.[2] Volcanoes within the caldera are known to have erupted eleven times in the last 21,000 years, with all but two of those eruptions being rhyolite.[12][4] The Rotoma eruptions are those of an embayment and the lateral magma erupted is associated with subsidence back to the eastern Rotoiti caldera margin. The Ōkareka Embayment to the west is also associated with caldera rim subsidence, this time the western shared rims of the Utu, Matahina and Rotoiti calderas.[2] Two of these eruptions, both at Tarawera, occurred within the last 2000 years (in 1886 and c. 1314AD). The most explosive of the eruptions in the last 21,000 years is likely to have been on the Haroharo vent alignment in about 5500 BCE, which ejected some 17 cubic kilometres of magma.[4] During the same period Ōkataina volcanos have contributed a total magma eruptive volume of about 80 km3 (19 cu mi) in all its eruptions.[12][13] In summary the more significant eruptions have been:[10][9][1]

Significant Eruptions Ōkataina Caldera (bold if caldera forming, dates corrected for multiple source uncertainity)[14]
Year before presentCalender dateEruptive nameVent / Vent aligment / CalderaVolume eruptedNotes
137 cal.yr10 June 1886 CETaraweraTarawera1 km3 (0.24 cu mi) DREBasaltic eruption[10][9][1][14]
709 ± 12 cal.yr1314 ± 12 CEKaharoa tephraTarawera5 km3 (1.2 cu mi) DRE[10][15][14]
5526 ± 145 cal.yr3576 ± 145 BCEWhakataneHaroharo13 km3 (3.1 cu mi) DRE[10][14]
7940 ± 257 cal.yr5990 ± 257 BCEMamakuHaroharo17 km3 (4.1 cu mi) DRE[10][16][14]
9423 ± 120 cal.yr7473 ± 120 BCERotomaHaroharo8 km3 (1.9 cu mi) DRE[10][14]
14,009 ± 155 cal.yr12059 ± 155 BCEWaiohau tephraTarawera10 km3 (2.4 cu mi) DRE[10][14]
15,635 ± 412 cal.yr13685 ±412 BCERotorua tephraHaroharo4 km3 (0.96 cu mi) DRE[10][14]
17,496 ± 462 cal.yr15546 ± 462 BCERerewhakaaitu tephraTarawera5 km3 (1.2 cu mi) DRE[10][17][14]
23,525–370+230 cal.yr21575 BCEOkarekaTarawera8 km3 (1.9 cu mi) DRE[10][16][14]
25,171 ± 964 cal.yr23221 BCETe RereKawerau Caldera (Haroharo)13 km3 (3.1 cu mi) DRE[10]33,000 years ago Kawerau (previously called Kaingaroa and miss-assigned to be 200,000 years older)[1] now corrected to 25,171 years ago[14]
31,500 cal.yr29550 BCEUnit LUnknown8.1 km3 (1.9 cu mi) Tephra[18][19]
32,500 cal.yr30550 BCEOmataroaUnknown16.2 km3 (3.9 cu mi) Tephra[18][19]
32,800 cal.yr30850 BCEAwakeriUnknown0.77 km3 (0.18 cu mi) Tephra[18][19]
33,000 cal.yr31050 BCEMangaoneUnknown19.1 km3 (4.6 cu mi) Tephra[18][19]
34,500 cal.yr32550 BCEUnit HUnknown0.1 km3 (0.024 cu mi) Tephra[18][19]
35,000 cal.yr33050 BCEUnit GUnknown2.5 km3 (0.60 cu mi) Tephra[18][19]
36,100 cal.yr34150 BCEHauparuUnknown15.2 km3 (3.6 cu mi) Tephra[18][19]
36,700 cal.yr34750 BCETe MahoeUnknown0.9 km3 (0.22 cu mi) Tephra[18][19]
36,800 cal.yr34850 BCEMaketuUnknown11 km3 (2.6 cu mi) Tephra[18][19]
38,000 approx. cal.yr36050 BCEUnit C (Pupuwharau then Pongakawa)Unknown0.7 km3 (0.17 cu mi) Tephra[18][19]
39,000 approx. cal.yr37050 BCENgamotuUnknown4.6 km3 (1.1 cu mi) Tephra[18][19]
40,000 approx. cal.yr38050 BCEUnit AUnknown0.44 km3 (0.11 cu mi) Tephra[18]
49,000 approx. cal.yr47050 BCEEarthquake FlatEarthquake Flat[18]
about 50,000 cal.yr48050 BCE Rotoiti/Rotoehu tephraRotoiti Caldera (Haroharo)'130 km3 (31 cu mi) DREBasalt was emplaced on the floor of the rhyolitic reservoir.[18] [Notes 1][19]
50,000 + cal.yr48050 BCEMatahi ScoriaSuspected to be Rotoiti CalderaBasaltic immediately pre-Rotoiti[13][18]
about 51,00049050 BCEPuhipuhi DacitePuhipuhi Embayment48,000+[1] ie is definitely before Rotoiti but age depends on actual Rotoiti age.
96,000 approx. cal.yr94050 BCEMoerangiMoerangi Dome[18]
188,000 approx. cal.yr186050 BCETutaeheke/Hap-KapengaTutaeheke Dome[18]
240,000 + cal.yr238050 BCEPokopoko pyroclasticsUnknown[18]
240,000 + cal.yr238050 BCEOnuku pyroclasticsUnknown[18]
280,000 cal.yr278000 BCEMatahinaMatahina Caldera150 km3 (36 cu mi) DRERecharging basalt found on top igmibrite layer.[18] [10] The latest age (not literature peer reviewed) is claimed at 322,000 ± 7,000 [20] which appears to be a reversion to the initial uncorrected timing. Also previously timed 230,000.[1] - large as caldera collapse
280,000 + cal.yr280000 BCEMatawhauraMatawhaura Dome[18]
280,000 + cal.yr280000 BCEMurupara pyroclasticsUnknown[18]
280,000 + cal.yr280000 BCEWairuaWairua Dome[18]
280,000 + cal.yr280000 BCEMaunawhakamanaMaunawhakamana Dome[18]
280,000 + cal.yr280000 BCEWhakapoungakauWhakapoungakau DomeLost volume with Matahini eruption[18]
557,000 cal.yr555000 BCEUtuUtu Caldera[13]
625,000 cal.yr623000 BCEŌkatainaŌkataina[9]


Tectonics

Faults are not defined under this very active caldera but the existence of at least one paired eruption at the far north and south extremes of the caldera about 50,000 years ago at Earthquake Flat and at Rotoiti suggest potential volcanicotectonic interaction. The active Paeroa Fault terminates at the caldera edge and the active Ngapouri-Rotomahana Fault is just to the south. The two recently active main vent alignments in the Ōkataina Caldera being the Horahora and Tarawera vents are parallel with these identifiable faults outside the caldera, however the faults are not on the exact vent line.[1] In the last 9,500 years four of the seven major ruptures of the Manawahe Fault have been associated in time with an volcanic eruption of the Okataina volcanic centre. This fault is just to the east of Lake Rotoma at the boundary between the tectonic Whakatane and the magmatic Ōkataina segments of the Taupō Rift. These are the Whakatane eruption of about 5500 years ago, the Mamaku eruption of about 8000 years ago and at least two fault ruptures in before or during the Rotoma eruption of 9500 years ago.[10] Similarly the Ngapouri-Rotomahana Fault and Paeroa Fault have multiple ruptures associated in time with volcanism including immediately prior to the Mamaku and Rotoma rhyolite eruptions in the case of the Paeroa Fault and of the Ngapouri-Rotomahana Fault immediately prior to the Kaharoa eruption.[8] At least 30% of major Taupō Volcanic Zone eruptions have now been associated with significant local fault ruptures within 30 km (19 mi) of the eruption.[10]

Notes
  1. Ages assigned to the Rotoiti/Rotoehu eruptives currently appear to vary depending upon methodology by about 15,000 years in the literature. This is problematic as many ages of volcanics in the Northern North Island would be more definite if a single agreed value existed. The issue of previous inaccurate age assignment started with a new figure for Rotoehu Ash of 64,000 ± 1650 cal.yr.(Wilson et al 1992) which was initially widely accepted. The youngest age assigned is 44,300 years ago (Shane et al 2003). The problems with some older techniques were possibly not resolved with new techniques that could explain the discrepancy and that resulted in 47,400 ± 1500 years ago (Flude et al 2016), as one recent peer reviewed work gave 61,000 ± 1400 cal.yr (Villamor et al 2022). Other chronology studies have a younger date of 45,200 ± 1650 cal.yr. (Danišík et al 2020 and 2012), 47,400 ± 1500 years ago (Gilgour et al 2008), and before these 65,000 years ago (Spinks 2005). For more on this age issue see notes to Puhipuhi Embayment.

References
  1. Spinks, Karl D. (2005). Rift Architecture and Caldera Volcanism in the Taupo Volcanic Zone, New Zealand (Thesis).
  2. 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.
  3. McKinnon, M., "Okataina caldera and its neighbours," Te Ara - Encyclopedia of New Zealand, 1 May 2015. Retrieved 11 June 2022.
  4. "Okataina Volcanic Centre Geology," GNS science. Retrieved 11 June 2022.
  5. Bertrand, E.A.; Kannberg, P.; Caldwell, T.G.; Heise, W.; Constable, S.; Scott, B.; Bannister, S.; Kilgour, G.; Bennie, S.L.; Hart, R.; Palmer, N. (2022). "Inferring the magmatic roots of volcano-geothermal systems in the Rotorua Caldera and Okataina Volcanic Centre from magnetotelluric models". Journal of Volcanology and Geothermal Research. 431 (107645): 107645. doi:10.1016/j.jvolgeores.2022.107645. ISSN 0377-0273. S2CID 251526385.
  6. Rooyakkers, S.M.; Faure, K.; Chambefort, I.; Barker, S.J.; Elms, H.C.; Wilson, C.J.; Charlier, B.L. (2023). "Tracking Magma‐Crust‐Fluid Interactions at High Temporal Resolution: Oxygen Isotopes in Young Silicic Magmas of the Taupō Volcanic Zone". Geochemistry, Geophysics, Geosystems. 24 (1). doi:10.1029/2022GC010694.
  7. Benson, Thomas W.; Illsley-Kemp, Finnigan; Elms, Hannah C.; Hamling, Ian J.; Savage, Martha K.; Wilson, Colin J. N.; Mestel, Eleanor R. H.; Barker, Simon J. (2021). "Earthquake Analysis Suggests Dyke Intrusion in 2019 Near Tarawera Volcano, New Zealand". Frontiers in Earth Science. 8. doi:10.3389/feart.2020.606992. ISSN 2296-6463.
  8. Berryman, Kelvin; Villamor, Pilar; Nairn, Ian; Begg, John; Alloway, Brent V.; Rowland, Julie; Lee, Julie; Capote, Ramon (2022). "Volcano-tectonic interactions at the southern margin of the Okataina Volcanic Centre, Taupō Volcanic Zone, New Zealand". Journal of Volcanology and Geothermal Research. 427 (107552). doi:10.1016/j.jvolgeores.2022.107552. ISSN 0377-0273.
  9. Cole, J.W., Deering, C.D., et al (2014) "Okataina Volcanic Centre, Taupo Volcanic Zone, New Zealand: A review of volcanism and synchronous pluton development in an active, dominantly silicic caldera system", Earth-science reviews, 128, 1–17. Abstract retrieved 11 June 2022.
  10. Villamor, Pilar; Litchfield, Nicola J.; Gómez-Ortiz, David; Martin-González, Fidel; Alloway, Brent V.; Berryman, Kelvin R.; Clark, Kate J.; Ries, William F.; Howell, Andrew; Ansell, India A. (2022). "Fault ruptures triggered by large rhyolitic eruptions at the boundary between tectonic and magmatic rift segments: The Manawahe Fault, Taupō Rift, New Zealand". Journal of Volcanology and Geothermal Research. 427. doi:10.1016/j.jvolgeores.2022.107478. ISSN 0377-0273.
  11. Gilgour, G.N.; Smith, R.T. (2008). "Stratigraphy, dynamics, and eruption impacts of the dual magma Rotorua eruptive episode, Okataina Volcanic Centre, New Zealand" (PDF). New Zealand Journal of Geology & Geophysics. 51 (4): 367–378. doi:10.1080/00288300809509871. S2CID 128976717.
  12. 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. S2CID 129365367.
  13. 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.
  14. Lowe, David; Ilanko, Tehnuka. "Pre-conference tephra data workshop – Hands-on session II: tephra excursion, Okareka Loop Road (29 January 2023)". Retrieved 2023-03-21.
  15. Froggatt, P. C.; Lowe, D. J. (1990). "A review of late Quaternary silicic and some other tephra formations from New Zealand: Their stratigraphy, nomenclature, distribution, volume, and age". New Zealand Journal of Geology and Geophysics. 33 (1): 89–109. doi:10.1080/00288306.1990.10427576.
  16. Darragh, Miles; Cole, Jim; Nairn, Ian; Shane, Phil (2006). "Pyroclastic stratigraphy and eruption dynamics of the 21.9 ka Okareka and 17.6 ka Rerewhakaaitu eruption episodes from Tarawera Volcano, Okataina Volcanic Centre, New Zealand". New Zealand Journal of Geology and Geophysics. 49 (3): 309–328. doi:10.1080/00288306.2006.9515170. S2CID 59137127.
  17. Shane, Phil; Martin, S.B.; Smith, Victoria C.; Beggs, K.R. (2007). "Multiple rhyolite magmas and basalt injection in the 17.7 ka Rerewhakaaitu eruption episode from Tarawera volcanic complex, New Zealand". Journal of Volcanology and Geothermal Research. 164 (1–2): 1–26. doi:10.1016/j.jvolgeores.2007.04.003.
  18. Bouvet de Maisonneuve, C.; Forni, F.; Bachmann, O. (2021). "Magma reservoir evolution during the build up to and recovery from caldera-forming eruptions – A generalizable model?". Earth-Science Reviews. 218. doi:10.1016/j.earscirev.2021.103684. ISSN 0012-8252.
  19. Danišík, Martin; Lowe, David J.; Schmitt, Axel K.; Friedrichs, Bjarne; Hogg, Alan G.; Evans, Noreen J. (2020). "Sub-millennial eruptive recurrence in the silicic Mangaone Subgroup tephra sequence, New Zealand, from Bayesian modelling of zircon double-dating and radiocarbon ages" (PDF). Quaternary Science Reviews. 246. doi:10.1016/j.quascirev.2020.106517. ISSN 0277-3791.
  20. Kidd, Maia Josephine (2021). Landscape Evolution in Ignimbrite Terrain: a study of the Mamaku Plateau, Taupō Volcanic Zone, New Zealand - Masters thesis, University of Canterbury (PDF) (Thesis).
This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.