Mayor Island / Tūhua

Mayor Island / Tūhua
Native name:
Tūhua (Māori)
Mayor Island / Tūhua as seen from Mount Maunganui
Map
Mayor Island / Tūhua surface volcanics map with the predominant rhyolitic volcanics coloured violet. The approximate submarine Tūhua volcanic field extent is shown in grey. The island to Tūhua's south coloured in orange-red is Mōtītī which has a basaltic andesite`origin.
Legend
  • Key for the volcanics that are shown with panning is:
  •   basalt (shades of brown/orange)
  •   monogenetic basalts
  •   undifferentiated basalts of the Tangihua Complex in Northland Allochthon
  •   arc basalts
  •   arc ring basalts
  •   dacite
  •   andesite (shades of red)
  •   basaltic andesite
  •   rhyolite (ignimbrite is lighter shades of violet)
  •   plutonic
  • White shading is selected caldera features.
  • Clicking on the rectangle icon enables full window and mouse-over with volcano name/wikilink and ages before present.
Mayor Island / Tūhua is located in New Zealand
Mayor Island / Tūhua
Mayor Island / Tūhua
Mayor Island / Tūhua is located in North Island
Mayor Island / Tūhua
Mayor Island / Tūhua
Geography
LocationBay of Plenty, North Island, New Zealand
Coordinates37°17′S 176°15′E / 37.283°S 176.250°E / -37.283; 176.250
Area13 km2 (5.0 sq mi)
Highest elevation355 m (1165 ft)
Administration
New Zealand
Demographics
Population4

Mayor Island / Tūhua is a dormant shield volcano located 26 km (16 mi) off the Bay of Plenty coast of New Zealand's North Island. It covers 13 km2 (5 sq mi).

Geography

The island is quite steep along its coast and rises to 355 metres (1,165 ft) above sea level. The closest major port entrance is at Tauranga, 35 km (22 mi) away to the southeast and it is 26 km (16 mi) from the Bay of Plenty coast.[1] A saddle about 75 metres (246 ft) deep separates it from the North Island, while the other side of the volcano rises from the seafloor some 400–500 metres (1,312–1,640 ft) beneath the waves.[2] Approximately 18,000 years ago during the Last Glacial Maximum when sea levels were over 100 metres (330 ft) lower than present day levels, Mayor Island / Tūhua was connected to the rest of New Zealand. Sea levels began to rise 7,000 years ago, separating Mayor Island / Tūhua from the mainland.[3] Hot springs may be found on the island's northern side, and there are two small crater lakes, Lake Aroarotamahine (Green Lake) and Lake Te Paritu (Black Lake).[4] These lie within the calderas formed in explosive eruptions.

Geology

Mayor Island is characterised as a peralkaline volcano and has exhibited a wide range of eruptive styles, including lava fountains, Strombolian explosions, extrusion of lava domes, phreatomagmatic explosions, Plinian falls and ignimbrite. It is the largest and most complex volcano located in the southwest margin of the 128 edifice Tūhua volcanic field which covers at least 510 km2 (200 sq mi) of the ocean floor.[5] This field is a polygenetic volcanic field, although up to 55 of the volcanoes are likely monogenetic, having only erupted once.[5]: 69 

Three caldera forming events have occurred named, C1 at 36 thousand years BP, C2, perhaps a gradual collapse, at about 9,200 years BP and C3 as a VEI 5 event at 7,600 ± 100 years BP.[6]

The most recent lava flows were historically dated by appearance at between 500 and 1,000 years old,[7][8] however radiocarbon dating of lake sediments is consistent with volcanic activity destroying pre-existing vegetation about a thousand years earlier than this.[9][5]: 122 

The Tūhua Caldera formed in the >1 km3 (0.24 cu mi) eruptive volume C3 event that occurred at 5650 ±100 BCE and is also a partial collapse crater.[10] It is 2.2 km (1.4 mi) by 2.5 km (1.6 mi) in size.[11] The Tuhua Tephra is quite distinctive and due to it having two dispersion patterns has been found in the Auckland area where it is up to 7 cm (2.8 in) thick, at Rotorua up to 10 cm (3.9 in) thick and Lake Waikaremoana where it is 4 cm (1.6 in) thick, making it useful as a mid-Holocene marker horizon.[11] It has also been characterised from multiple sea bed cores off the East coast from the Havre trough off the Bay of Plenty to the southern North Island off Cape Turnagain.[11] Te Paritu Tephra is assigned to a Mayor Island eruption [11] but the full recent significant eruptive sequence required sea cores as prevailing winds are off land.[12] In summary recent eruptions are:[13]

Mayor Island eruptions
Phases Tephra/eruption name(s) Date before present (ka BP) Comment
Early cone building phase 150from ~150 Consistently rhyolitic peralkaline eruptives, with two large and complex lava shields at north-east and south-west of island[5]: 21 . includes during period Orongatea pumice cone and Pre-Rotoiti lava which are presently poorly constrained in time.[5]: 27 
NE lava shield 147 [5]: 27 
- 131 Te Araata Lavas [5]: 27 
- 118 Te Araata Lavas [5]: 27 
Oturu pumice 55 [5]: 27 
M1 86.3 As far north as Auckland and marine deposits[12]
Oturu pumice 55 [5]: 27 
54.9to 55
Pre-caldera phase 54.5from 55 Up to 5 explosive episodes of Strombolian to sub-Plinian/Plinian scale and multiple small scale flank eruptions[5]: 22 
Post Rotoiti lavas 46 [5]: 27 
M2 45 Tephra[5]: 27 
- 44.0 44 ± 20 Lava flow[5]: 22 
M3 40.5 40.5 ± 5 Tephra and lava flow[12][5]: 227 
M4 (Mayor Island) 37.4 Tephra[5]: 22 
36.5to 36
Inter-caldera phase 36.1from 36 [5]: 23 
- 36 Rim lavas and Upper Taratimi tephras[5]: 27 
Paratao lava 33 [5]: 27 
Opo Bay lava and tuff ring 25.4 [5]: 27 
Ruamata lava and tuff ring 24 [5]: 27 
M5 22.2
- 17.36 Pyroclastic cone, Edifice 2 and Turanganui lavas,[5]: 27 
Te Paritu Tephra 17 [5]: 27 
14.4to 14.2
Caldera C2 phase 14.3from 14.2 [5]: 23 
M6 14.2 [12]
- 14 land tephra layer[5]: 27 
- 11.5 marine tephra layer[5]: 27 
Caldera C2 lavas 9.2 includes dome and splatter lava eruptions[5]: 27 
Upper Taumou Pa lava 9.2 [5]: 27 
Pupuke maar macrotephra 8.7 [5]: 27 
8.69 to 8.7
Caldera C3 phase M7 (Tuhua) 7.6 7.6 ± 1 VEI 5[14][6]
Post C3 volcanism 7.5 from 7.6 [6]
- 2.9 2.898 ± 82 C3 lavas[5]: 26 
- 2.4 Tarawakoura, Lake Te Paritu core[9]
- 2.2 2.223 ± 60 Tarawakoura, Lake Te Paritu core[9]

The tephra can contain a distinctive purple crystal mineral tuhualite (Na,K)Fe2Si6O15 which the island's volcano was only known source of, until 2016.[15][16]

Risks

The island would likely be sterilised in a major pyroclastic eruption as last occurred about 7,000 years ago, although a small eruption could be confined within the caldera. Tsunami activity and ash affecting the Bay of Plenty are possible with initial vent clearing and ash falls toward the major cities of the northern half of the North island being most likely in summer, with economic disruption to especially ports and airports.[17] Large ash fall over land would devastate agriculture and ecosystems for some time due to fluorosis and chlorine poisoning as happened after the 1783 eruption at Laki, in Iceland.[5]: 172–173  Usually however the ash fall will be away from land. However it has been estimated that a worse case tsunami could be 35 m (115 ft) high when it reached Bay of Plenty coastal resorts and the city of Tauranga with possibly only 30 minutes warning. Most of the infrastructure of these coastal towns is less than 15 m (49 ft) above sea level so is at risk of complete destruction.

History

Tūhua is the ancestral home of Te Urungawera, hapū of Te Whānau a Tauwhao within the iwi of Ngāi Te Rangi.[1] The island is considered special by Māori (the indigenous people of New Zealand) partly because of the presence of black obsidian, a volcanic glass created by the rapid cooling of silica-rich lava, prized as a cutting tool. The obsidian was called Tūhua by Māori, who called the island by the same name.[18][1] Over 80% of obsidian excavated from Matakawau on Great Mercury Island had been sourced from Tūhua.[19] Several pa sites are known on the island, the final of which was inhabited until 1901.

Captain James Cook called it the Mayor when he sighted it on 3 November 1769,[1] in recognition of the Lord Mayor's Day to be held in London a few days later.

The Ngāti Whakaue led a military expedition to the island in 1842, after a tribesman was killed by the Whanau a Tauwhao, a hapu of Ngāi Te Rangi[20]

Uses and recreation

The island, since 2014 has been administered by the Tūhua Trust Board,[21] and access is restricted.[4] Since 1953 it has been a wildlife refuge.[1][4] The area of the Bay of Plenty around the island is renowned for game fishing, with marlin, mako sharks, and swordfish all inhabiting the surrounding waters. Since 1990 the island itself, has no longer been the base for big game fishing.[1] Some of the waters close to the island, since 1993, are a small marine reserve.[1][22] There are several tramping tracks around the island, and it is also popular with divers. A small number of holiday houses are located in Opo Bay on the south coast of the island, along with a camp ground and a few rental cabins.[23] The 2001 census showed a population of three, after zero in 1996 and 12 in 1991 (all figures randomised for privacy on a Base-3 system).[24] There are no permanent residents presently but the island is usually occupied during the summer months.[4]

See also

References

  1. ^ a b c d e f g "Tūhua (Mayor Island) (Place)". Tauranga: Tauranga City Libraries. Archived from the original on 8 November 2025. Retrieved 31 January 2026.
  2. ^ New Zealand Hydrographic Chart Number 541: Mayor Island to Town Point (Okurei Point), Land Information New Zealand. Retrieved 29 April 2009.
  3. ^ "Estuary origins". National Institute of Water and Atmospheric Research. Retrieved 3 November 2021.
  4. ^ a b c d "Tūhua/Mayor Island Visitor Information" (PDF). 2018. Retrieved 1 February 2026.
  5. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae Kuethe, J.R. (2024). Chemical and Physical controls on Explosive-Effusive transitions at Peralkaline volcanoes. Tūhua Island, New Zealand (Doctoral dissertation) (Thesis). School of Environment, The University of Auckland. pp. 1–284. Retrieved 1 February 2026.
  6. ^ a b c Kósik, S.; Németh, K.; Rees, C. (2022). "Integrating LiDAR to unravel the volcanic architecture and eruptive history of the peralkaline Tuhua (Mayor Island) volcano, New Zealand". Geomorphology. 418. 108481. Bibcode:2022Geomo.41808481K. doi:10.1016/j.geomorph.2022.108481.
  7. ^ Houghton, B.F.; Wilson, J. N. C; Weaver, S.D.; Lanphere, M.A.; Barclay, J (1995). "Mayor Island Geology". Volcanic Hazards at Mayor Island. [Palmerston North, NZ]: Ministry of Civil Defence. Volcanic Hazards Information Series 6.: 1–23.
  8. ^ Houghton, Bruce F.; Weaver, S.D.; Wilson, J. N.; Lanphere, M.A. (1992). "Evolution of a quaternary peralkaline volcano: Mayor Island, New Zealand". Journal of Volcanology and Geothermal Research. 51 (3): 217–236. Bibcode:1992JVGR...51..217H. doi:10.1016/0377-0273(92)90124-V.
  9. ^ a b c Empson, L.; Flenley, J.; Sheppard, P. (2002). "A dated pollen record of vegetation change on Mayor Island (Tuhua) throughout the last 3000 years". Global and Planetary Change. 33 (3): 329–337. Bibcode:2002GPC....33..329E. doi:10.1016/S0921-8181(02)00086-3.
  10. ^ Lowe, D. J.; Balks, M. R. (2019). "Introduction to Tephra-Derived Soils and Farming, Waikato-Bay of Plenty, North Island, New Zealand" (PDF).
  11. ^ a b c d Manighetti, B.; Palmer, A.; Eden, D.; Elliot, M. (2003). "An occurrence of Tuhua Tephra in deep‐sea sediments from offshore eastern North Island, New Zealand". New Zealand Journal of Geology and Geophysics. 46 (4): 581–590. doi:10.1080/00288306.2003.9515031. S2CID 131253941.
  12. ^ a b c d Shane, Phil; Sikes, E.L.; Guilderson, T.P. (2006). "Tephra beds in deep-sea cores off northern New Zealand: implications for the history of Taupo Volcanic Zone, Mayor Island and White Island volcanoes". Journal of Volcanology and Geothermal Research. 154 (3–4): 276–290. doi:10.1016/j.jvolgeores.2006.03.021. ISSN 0377-0273.
  13. ^ Loame, Remedy Charlotte (2016). Using a tephrostratigraphic framework to determine the past 40,000 yrs of fault rupture and paleohydrothermal activity on the east strand of the Whirinaki Fault, Ngakuru Graben, central Taupo Volcanic Zone (PDF) (Thesis).
  14. ^ "Global Volcanism Program: Mayor Island". Washington DC: Global Volcanism Program. Retrieved 1 February 2026.
  15. ^ Nathan, Simon (2009). "Rock and mineral names – Mineral names – 1, Te Ara – the Encyclopedia of New Zealand". Retrieved 31 January 2026.
  16. ^ Baginski, B.; Macdonald, R.; White, C.; Jezak, L. (2018). "Tūhualite in a peralkaline rhyolitic ignimbrite from Pantelleria, Italy". European Journal of Mineralogy. 30 (2): 367–373. Bibcode:2018EJMin..30..367B. doi:10.1127/ejm/2018/0030-2711.
  17. ^ Buck, M.D. (1985). "An assessment of volcanic risk on and from Mayor Island, New Zealand". New Zealand Journal of Geology and Geophysics. 28 (2): 283–298. doi:10.1080/00288306.1985.10422227.
  18. ^ McKinnon, Malcolm. "Bay of Plenty region – Māori traditions, Te Ara – the Encyclopedia of New Zealand". Retrieved 31 January 2026.
  19. ^ Furey, Louise; Emmitt, Joshua; Wallace, Roderick (2017). "Matakawau Stingray Point Pa Excavation, Ahuahu Great Mercury Island 1955–56". Papahou: Records of the Auckland Museum. 52: 39–57. doi:10.32912/RAM.2018.52.3. ISSN 1174-9202. JSTOR 90016661. Wikidata Q104815050.
  20. ^ Paterson, Lachy; Wanhalla, Angela (21 August 2017). He Reo Wahine: Maori Women's Voices from the Nineteenth Century. Auckland University Press. ISBN 978-1-77558-927-3.
  21. ^ "Tuhua Island District Plan". Wellington: Department of Internal Affairs. 2021. Retrieved 31 January 2026.
  22. ^ "Tūhua (Mayor Island) Marine Reserve". Retrieved 27 August 2022.
  23. ^ "Places". Archived from the original on 1 December 2008. Retrieved 17 January 2007.
  24. ^ Census Archived 15 February 2016 at the Wayback Machine
allikas: https://en.wikipedia.org/wiki/Mayor_Island/Tuhua