Ōkataina Caldera
Ōkataina Caldera | |
---|---|
Ōkataina Volcanic Centre, Okataina Caldera, Okataina Volcanic Centre | |
Highest point | |
Coordinates | 38°10′S 176°30′E / 38.167°S 176.500°E |
Dimensions | |
Length | 28 km (17 mi)[1] |
Width | 15 km (9.3 mi)[1] |
Geography | |
Country | Ma)[2] |
Mountain type | Caldera |
Volcanic region | Taupō Volcanic Zone |
Last eruption | 1886 Tarawera, 1973 Hydrothermal in Waimangu Volcanic Rift Valley |
Climbing | |
Access | State Highway 5 (New Zealand) |
Ōkataina Caldera (Ōkataina Volcanic Centre, also spelled Okataina) is a volcanic caldera and its associated volcanoes located in Taupō Volcanic Zone of New Zealand's North Island. It has several actual or postulated sub calderas. The Ōkataina Caldera is just east of the smaller separate Rotorua Caldera and southwest of the much smaller Rotomā Embayment which is usually regarded as an associated volcano. It shows high rates of explosive rhyolitic volcanism although its last eruption was basaltic. 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 defined by gravitational and magnetic features.[3]: 14 .[a] Since 2010 other terms such as the Haroharo vent alignment, Utu Caldera, Matahina Caldera, Rotoiti Caldera and a postulated Kawerau Caldera are often used,[2] rather than a Haroharo Caldera classification.[3]: 2
Geography
The caldera covers an area of about 450 square kilometres (170 sq mi), stretching from
Geology
The overwhelming volcanic deposits are
Eruptions
The caldera has seen six eruptions in the past 10,000 years, most recently the
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.[7] 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.[7] 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.[9]
Eruption mechanism
The underlying
Any basaltic magmas that do reach the surface will have traversed this complicated crustal region and may erupt as a dyke. This is believed to have happened with the 1886 Mount Tarawera eruption.[2]
History
It is likely that the volcanic history of the area began some 625,000 years ago.[12] The caldera was formed by at least five huge eruptions between 400,000 and 50,000 years ago.
The oldest eruptive sub caldera is called the Utu caldera and is located in the south central portion. The basement of this sub caldera is 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.[13] This collapse was associated with eruption of the Matahina Ignimbrite which covers over 2,000 km2 (770 sq mi) of the central North Island.[1] The second major phase Matahina sub caldera is to the south east and its basement is also about 5 km (3.1 mi) below present ground level.[2] The original shape of the Matahina caldera has been modified (and buried/destroyed) by various events including at least eight smaller eruptions between 70,000 and 24,000 years ago. For example the dacite Puripuri basin/embayment is a subsidence related feature. This subsidence is related to the lateral movement of the underlying magma towards the eastern caldera margins.[2]
The paired eruptions approximately 50,000 years ago[14] of Rotoiti and at Earthquake Flat at far northern and southern ends of the caldera respectively had eruptive volumes of 120 cubic kilometres (29 cu mi) and 10 cubic kilometres (2.4 cu mi).[1] The resulting Rotoiti sub 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 it is unknown where the eruptions were centered. One of these events can be assigned to the Kawerau ignimbrite eruption of 33,000 years ago, with its location within the central part of the Matahina Caldera at level of the Puhipuhi Basin.[1] An area of low gravity on gravimetric studies is consistent with the fourth phase Kawerau Caldera being here and its basement being about 2 km (1.2 mi) below present ground level.[2]
Although the latest caldera models include the Haroharo vent alignment they do not allow for the separate existence of a
More recently 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.
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 at about 5500
In summary the more significant eruptions have been:[13][12][1]
Year before present | Calendar date | Eruptive name | Vent / Vent alignment / Caldera | Volume erupted | Notes |
---|---|---|---|---|---|
138 cal.yr | 10 June 1886 CE | Tarawera | Tarawera | 1 km3 (0.24 cu mi) DRE | Basaltic eruption[13][12][1][17] |
710 ± 12 cal.yr | 1314 ± 12 CE | Kaharoa tephra | Tarawera | 5 km3 (1.2 cu mi) DRE | [13][18][17] This eruption was immediately preceded by a rupture on the Edgecumbe fault.[19] |
3710 ± 10 cal.yr | 1760 ± 10 BCE | Rotokawau | Rotokawau | - | Basaltic eruption[20]: 21 [21][22] |
5526 ± 145 cal.yr | 3576 ± 145 BCE | Whakatane | Haroharo | 13 km3 (3.1 cu mi) DRE | [13][17] |
7940 ± 257 cal.yr | 5990 ± 257 BCE | Mamaku | Haroharo | 17 km3 (4.1 cu mi) DRE | [13][23][17] |
9423 ± 120 cal.yr | 7473 ± 120 BCE | Rotoma | Haroharo | 8 km3 (1.9 cu mi) DRE | [13][17] |
14,009 ± 155 cal.yr | 12059 ± 155 BCE | Waiohau tephra | Tarawera | 10 km3 (2.4 cu mi) DRE | [13][17] |
15,635 ± 412 cal.yr | 13685 ±412 BCE | Rotorua tephra | Haroharo | 4 km3 (0.96 cu mi) DRE | [13][17] |
17,496 ± 462 cal.yr | 15546 ± 462 BCE | Rerewhakaaitu tephra | Tarawera | 5 km3 (1.2 cu mi) DRE | [13][24][17] |
23,525–370+230 cal.yr | 21575 BCE | Okareka | Tarawera | 8 km3 (1.9 cu mi) DRE | [13][17] [b] |
25,171 ± 964 cal.yr | 23221 BCE | Te Rere | Kawerau Caldera (Haroharo ) |
13 km3 (3.1 cu mi) DRE | [13]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[17] |
31,500 cal.yr | 29550 BCE | Unit L | Unknown | 8.1 km3 (1.9 cu mi) Tephra | [25][26] |
32,500 cal.yr | 30550 BCE | Omataroa | Unknown | 16.2 km3 (3.9 cu mi) Tephra | [25][26] |
32,800 cal.yr | 30850 BCE | Awakeri | Unknown | 0.77 km3 (0.18 cu mi) Tephra | [25][26] |
33,000 cal.yr | 31050 BCE | Mangaone | Unknown | 19.1 km3 (4.6 cu mi) Tephra | [25][26] |
34,500 cal.yr | 32550 BCE | Unit H | Unknown | 0.1 km3 (0.024 cu mi) Tephra | [25][26] |
35,000 cal.yr | 33050 BCE | Unit G | Unknown | 2.5 km3 (0.60 cu mi) Tephra | [25][26] |
36,100 cal.yr | 34150 BCE | Hauparu | Unknown | 15.2 km3 (3.6 cu mi) Tephra | [25][26] |
36,700 cal.yr | 34750 BCE | Te Mahoe | Unknown | 0.9 km3 (0.22 cu mi) Tephra | [25][26] |
36,800 cal.yr | 34850 BCE | Maketu | Unknown | 11 km3 (2.6 cu mi) Tephra | [25][26] |
38,000 approx. cal.yr | 36050 BCE | Unit C (Pupuwharau then Pongakawa) | Unknown | 0.7 km3 (0.17 cu mi) Tephra | [25][26] |
39,000 approx. cal.yr | 37050 BCE | Ngamotu | Unknown | 4.6 km3 (1.1 cu mi) Tephra | [25][26] |
40,000 approx. cal.yr | 38050 BCE | Unit A | Unknown | 0.44 km3 (0.11 cu mi) Tephra | [25] |
49,000 approx. cal.yr | 47050 BCE | Earthquake Flat | Earthquake Flat | [c][25] | |
about 50,000 cal.yr | 48050 BCE | Rotoiti/Rotoehu tephra | Rotoiti Caldera (Haroharo)' | 130 km3 (31 cu mi) DRE | Basalt was emplaced on the floor of the rhyolitic reservoir.[25] [d][27]: 188–90 [26][28] |
50,000 + cal.yr | 48050 BCE | Matahi Scoria | Suspected to be Rotoiti Caldera | Basaltic immediately pre-Rotoiti[16][25] | |
about 51,000 | 49050 BCE | Puhipuhi Dacite | Puhipuhi Embayment | 48,000+[1] ie is definitely before Rotoiti but age depends on actual Rotoiti age. | |
96,000 approx. cal.yr | 94050 BCE | Moerangi | Moerangi Dome | [25] | |
188,000 approx. cal.yr | 186050 BCE | Tutaeheke/Hap-Kapenga | Tutaeheke Dome | [25] | |
240,000 + cal.yr | 238050 BCE | Pokopoko pyroclastics | Unknown | [25] | |
240,000 + cal.yr | 238050 BCE | Onuku pyroclastics | Unknown | [25] | |
280,000 cal.yr | 278000 BCE | Matahina | Matahina Caldera |
150 km3 (36 cu mi) DRE | Recharging basalt found on top igmibrite layer.[25] [13] The latest age (not literature peer reviewed) is claimed at 322,000 ± 7,000 [29] which appears to be a reversion to the initial uncorrected timing. Also previously timed 230,000.[1] - large as caldera collapse |
280,000 + cal.yr | 280000 BCE | Matawhaura | Matawhaura Dome | [25] | |
280,000 + cal.yr | 280000 BCE | Murupara pyroclastics | Unknown | [25] | |
280,000 + cal.yr | 280000 BCE | Wairua | Wairua Dome | [25] | |
280,000 + cal.yr | 280000 BCE | Maunawhakamana | Maunawhakamana Dome | [25] | |
280,000 + cal.yr | 280000 BCE | Whakapoungakau | Whakapoungakau Dome | Lost volume with Matahini eruption[25] | |
557,000 cal.yr | 555000 BCE | Utu | Utu Caldera |
[16] | |
625,000 cal.yr | 623000 BCE | Ōkataina | Ōkataina | [12] |
Tectonics
Faults are not defined under this very active caldera. The active
Notes
- ^ Possibly started from
with the author presuming that certain ignimbrites came from this source. The term Haroharo Caldera was increasingly used in academic papers in the 1970's and 1980's but changed as the detailed geology became better understood. The difficulty was that by then the term Haroharo Caldera was established. The term is still used, and currently is defined by gravity and magnetic differences.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 - ^ Sources based on Darragh et al. 2006 give timings about 2000 years earlier for the Okareka eruption.[23]
- ^ This eruption is assigned by some to the Kapenga Caldera. See discussion in that article
- ^ 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), while one recent peer reviewed work gave 61,000 ± 1400 cal.yr (Villamor et al 2022). Other, mainly recent chronology studies have a younger date of 45,200 ± 1650 cal.yr. (Danišík et al 2020 and 2012), 45,100 ± 3300 years ago (Peti et al 2020), 47,400 ± 1500 years ago (Gilgour et al 2008), and before these 65,000 years ago (Spinks 2005). A recent review of 27 determinations gave the consensus range as between about 45 and about 55 cal ka (Hopkins et al. 2021). For more on this age issue see notes to Puhipuhi Embayment.
References
- ^ a b c d e f g h i j k Spinks, Karl D. (2005). Rift Architecture and Caldera Volcanism in the Taupo Volcanic Zone, New Zealand (Thesis).
- ^ S2CID 253783414.
- ^ ISSN 0377-0273.
- ^ Te Ara - Encyclopedia of New Zealand, 1 May 2015. Retrieved 11 June 2022.
- ^ S2CID 251914262.
- ISSN 0377-0273.
- ^ a b c d e "Okataina Volcanic Centre Geology," GNS science. Retrieved 11 June 2022.
- S2CID 251526385.
- S2CID 254807245.
- ISSN 2296-6463.
- ^ S2CID 248111450.
- ^ a b c d Cole, J.W., Deer ing, 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.
- ^ S2CID 246258923.
- S2CID 128976717.
- ^ S2CID 129365367.
- ^ S2CID 131562598.
- ^ a b c d e f g h i j k 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.
- hdl:10289/176.
- .: 83
- ^ Elms, Hannah Corinne (2022). Geochemistry, Magmatic Processes and Timescales of Recent Rhyolitic Eruptives of the Ōkataina Volcanic Centre, Taupō Volcanic Zone, Aotearoa/New Zealand: PhD thesis (Thesis). Te Herenga Waka—Victoria University of Wellington. pp. 1–316.
- ^ Beanland, S.; Houghton, B. (1991). "Rotokawau tephra: basaltic maars in Okataina volcanic centre, Taupo Volcanic Zone". Records N.Z. Geological Survey (43): 37–43.
- ISBN 978-0-478-19778-5. Retrieved 16 March 2024.: 49, 100
- ^ S2CID 59137127.
- .
- ^ S2CID 236237501.
- ^ S2CID 224864954.
- hdl:10289/14349.
- .
- ^ 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).