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Rangitoto Island

Coordinates: 36°47′12″S 174°51′36″E / 36.786742°S 174.860115°E / -36.786742; 174.860115
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This article is about the island in the Hauraki Gulf. For the islands in the Marlborough Sounds, see Rangitoto Islands. For the rural community in New Zealand's North Island, see Rangitoto, Waikato. For the mountain and range, see Rangitoto Range.

Rangitoto Island
Ngā Rangi-i-totongia-a Tama-te-kapua (Māori)
Oblique aerial of Rangitoto Volcano from the south
Rangitoto Island is located in New Zealand
Rangitoto Island
Rangitoto Island
Geography
LocationAuckland
Coordinates36°47′12″S 174°51′36″E / 36.786742°S 174.860115°E / -36.786742; 174.860115
Highest point260 m (850 ft)
Administration
New Zealand
Additional information
Age Meghalayan[1]
↓

Rangitoto Island is a volcanic island in the Hauraki Gulf near Auckland, New Zealand. The 5.5 km (3.4 mi) wide island is a symmetrical shield volcano cone capped by central scoria cones, reaching a height of 260 m (850 ft).[2][3] Rangitoto is the youngest and largest of the approximately 50 volcanoes of the Auckland volcanic field, having erupted in two phases about 1450 CE and 1500 CE [4][5] and covering an area of 2,311 ha (5,710 acres).[3][6] It is separated from the mainland of Auckland's North Shore by the Rangitoto Channel. Since World War II, it has been linked by a causeway to the much older, non-volcanic Motutapu Island.[7]

Rangitoto is Māori for 'Bloody Sky',[8] with the name coming from the full phrase Ngā Rangi-i-totongia-a Tama-te-kapua ("The days of the bleeding of Tama-te-kapua"). Tama-te-kapua was the captain of the Arawa waka (canoe) and was badly wounded on the island, after having lost a battle with the Tainui iwi (tribe) at Islington Bay.[6][9][10]

Geology

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The thin land bridge link between Rangitoto Island (left) and Motutapu Island is visible here from the air
The opening to a lava tube at Rangitoto, partially obstructed by tree growth

Rangitoto formed during two phases of eruptions that may have lasted only 5–10 years, about 600 years ago. The first part of the eruption sequence, dated by radiocarbon methods at about 627 years ago (= 553 ± 7 yrs BP)[11] was initially wet and produced surges of volcanic ash that mantled neighbouring Motutapu Island from alkaline olivine basalt eruptives sourced from the north cone area. The later part of the eruption dated at about 578 years ago (= 504 ± 5 yrs BP) was dry and built most of Rangitoto, erupting all the sub-alkaline basaltic lava flows of the shield and the southern scoria cone at the apex that mostly buried the north cone.[11][4] The 2.3 km3 (0.55 cu mi) of material that erupted from the volcano was nearly as much as the combined mass produced by all the previous eruptions in the Auckland volcanic field, which were spread over nearly 200,000 years.

Eruptive history

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In 2013, scientists from Auckland University reported that Rangitoto had been much more active in the past than previously thought, suggesting it had been active on and off for around 1000 years before the final eruptions around 600 years ago. This was based on recognition of a number of horizons of tiny volcanic glass shards, seemingly erupted from Rangitoto, in sediment cores from Lake Pupuke.[12] To test this hypothesis, a 150 m (490 ft) deep hole was drilled through the western flank of Rangitoto in February 2014. No supporting evidence for these hypothesised small eruptions up to 1000 yrs before the main eruption of Rangitoto was found. The University scientists did, however, core a thin basalt lava flow within marine sediment dated at 6000 years old, and hypothesised that this was an even earlier eruption from Rangitoto.[13][14] Civil Defence officials said the discovery did not make living in Auckland any more dangerous, but did change their view of how an eruption might proceed.[15] These headline-grabbing results were controversial and not accepted by all geologists.[16][17] In 2018 many of the original group of Auckland University geologists reported on their latest research and reinterpretation of the evidence and concluded that Rangitoto only erupted once, about 600 yrs ago, possibly in two phases.[18] The thin lava flow within 6000 yr-old sediment in the Rangitoto drillcore has exactly the same chemistry as the lowest/oldest flows of the cored shield volcano above and has recently been shown to also have the same U-Th-Ra signature and both must have been erupted and solidified at virtually the same time.[1] The thin "flow" is therefore likely to be basalt lava that was intruded into the sediment as the shield volcano was starting to be formed. This is similar to the situation seen on the coast at Queen Victoria Rock, near the Rangitoto Lighthouse, where lava flows have ploughed into the soft seafloor sediment and intruded into it, bringing at least one sediment slab up to high tide level.[19] Thus no evidence has been found so far to support the hypotheses of earlier eruptions of Rangitoto between 620 and 8000 yrs ago. It is possible that Rangitoto buried a smaller and much older and unrelated volcano,[14] a view possibly supported, but certainly not proven, by recent microfossil research from the marine sediments obtained from beneath Rangitoto in the stratigraphic drillhole.[20]

Structure

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View from inside one of the caves

The southern cone of Rangitoto Volcano with its own crater likely buries a more northern explosion crater and tuff ring formed during the early wet phase of eruption in the middle of the Waitemata Harbour.[4] The external form of Rangitoto consists of a circular, gently sloping shield composed of numerous overlapping lava flows. The centre of the volcano is capped by the remains of much steeper scoria cones made of loose scoria that was erupted by dry-style fire-fountaining from several vents. Gravitational studies show a relationship with the Islington Bay Fault which strikes between Rangitoto and Mototapu islands but which is distinctly offset by about 3.5 km (2.2 mi) from the Rangitoto vents to the east of the fault and that there is a density beneath the southern cones.[4] This along with magnetic studies has been interpreted to show a solidified intra-cone feeder dyke as the most likely explanation for the mass under the southern cone system and some buried mass to the north of the northern cone whose character can not be fully modelled but is likely to be a feeder dyke.[4] At depth of more than 6 km (3.7 mi) the magma may have initially tracked the Islington Bay Fault in this modelling.[4] Withdrawal of magma back down the throat of the volcano at the end of the eruptions has resulted in slight subsidence of the scoria cones. This has created a moat-like ring around the central scoria cones, which the main track to Rangitoto's summit passes through on the way to the summit and gives a distinctive shape to the island.[6][9] In some parts of the island, fields of clinker-like black basalt lava are exposed where vegetation has yet to colonise the surface of the youngest lava flows. About 200 metres from the top of the mountain on the eastern side visitors can walk through sections of two lava tubes — cave-like tubes left behind after the passage of liquid lava. The more accessible of the caves are signposted.[9] Lava tubes are formed when low-viscosity molten lava known as pahoehoe flows and cools on the outside due to contact with the ground and air, to form a hard crust allowing the still-liquid molten lava to continue to flow through inside. In several places the lava tube roof has collapsed thus providing several different entrances to the one elongate tube. A torch is needed to explore the caves. The longest known cave is about 120 m long.[21]

Biology

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Pterostylis growing on Rangitoto

Because there are virtually no streams on the island, plants rely on rainfall for moisture. It has the largest forest of pohutukawa trees in the world,[6] as well as many northern rātā trees. In total, more than 200 species of trees and flowers thrive on the island, including several species of orchid, as well as more than 40 types of ferns.[9] The vegetation pattern was influenced by the more recent eruptions creating lava flow crevices where pōhutukawa trees (Metrosideros ssp.) grow.[22]

Lava field with path and encroaching vegetation

The island is considered especially significant because all stages from raw lava fields to scrub establishment and sparse forests are visible. As lava fields contain no soil of the typical kind, windblown matter and slow breaking-down processes of the native flora are still in the process of transforming the island into a more habitable area for most plants (an example of primary succession), which is one of the reasons why the local forests are relatively young and do not yet support a large bird population. However, the Kākā, a New Zealand-endemic parrot, is thought to have lived on the island in pre-European times.[9]

Goats were present on Rangitoto in large numbers in the mid 19th century and survived until the 1880s.[23] Fallow deer were introduced to Motutapu in 1862 and spread to Rangitoto, but disappeared by the 1980s. The brush-tailed rock-wallaby was introduced to Motutapu in 1873, and was common on Rangitoto by 1912, and the brushtail possum was introduced in 1931 and again in 1946. Both were eradicated in a campaign from 1990 to 1996 using 1080 and cyanide poison and dogs. The eradication campaign did not have a significant effect on bird species diversity and abundance, due to the presence of other predators.[24]

Stoats, rabbits, mice, rats, cats and hedgehogs remained a problem on the island,[23][25] but the Department of Conservation (DOC) aimed to eradicate them beginning with the poisoning of black rats, brown rats and mice and in August 2011, both Rangitoto and neighbouring Motutapu Islands were officially declared pest-free with both islands now also boasting populations of newly translocated North Island saddlebacks.[26]

As the area is a DOC-administered reserve (in partnership with the tangata whenua Ngāi Tai and Ngāti Paoa),[8] visitors may not take dogs or other animals onto the islands.[27]

The main vent of Rangitoto Island, now totally forested

History

[edit]

Māori association

[edit]
Bracken fern, Pteridium esculentum, Rangitoto Island

The volcano erupted within the historical memory of the local Māori iwi (tribes).[9][10] Human footprints have been found between layers of Rangitoto volcanic ash on the adjoining Motutapu Island.[10] Ngāi Tai was the iwi living on Motutapu, and considers both islands their ancestral home. Ngāti Paoa also has links with Rangitoto.[28]

The name Rangitoto literally means "red sky", and is linked to a traditional story of a fight between Tama-te-kapua, captain of the Arawa canoe, and Hoturoa, captain of the Tainui canoe. The name Ngā Rangi-i-totongia-a Tama-te-kapua ("The days of the bleeding of Tama-te-kapua") refers to how Tama-te-kapua was injured in the fight.[29] The peaks of the island were known by the names Ngā Pona Toru o Peretū ("The Three Knuckles of Peretū") or Ngā Tuaitara o Taikehu ("The Dorsal Fins of Taikehu").[29] Ngā Pona Toru o Peretū, often shortened to Peretū is the traditional Ngāi Tai ki Tāmaki name for the three peaks of the island, and was a name given by Taikehu, a captain of the Tainui canoe.[30]

Rangitoto is associated with many traditional stories and myths. One involves Tiriwa (the namesake of the traditil name for the Waitākere Ranges, Te Wao Nui o Tiriwa), a chief of the supernatural Tūrehu people, who uplifted Rangitoto from Karekare on the west coast, as a show of his strength.[31] Others involve a 'tupua' couple, children of the Fire Gods. After quarreling and cursing Mahuika, the fire-goddess, they lost their home on the mainland because it was destroyed by Mataoho, god of earthquakes and eruptions, on Mahuika's behalf. Lake Pupuke on the North Shore was created in the destruction, while Rangitoto rose from the sea. The mists surrounding Rangitoto at certain times are called the tears of the tupua for their former home.[9]

Since European colonisation

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The island was purchased for £15 by the Crown in 1854, very early in New Zealand's colonisation by Europeans, and for many years served as a source of basalt for the local construction industry.[32] It was set aside as a recreation reserve in 1890, and became a favourite spot for daytrippers.[32] Some development occurred nonetheless. In 1892, salt works were created on 5 acres (20,000 m2) near Mackenzies Bay. The wharf and summit road were opened in 1897, with another road linking the summit to Islington Bay by 1900.[33] For over 30 years (from 1898 to 1930), scoria was quarried from near the shoreline on the west side of Islington Bay[34] as building material for Auckland.[35]

View of Rangitoto Island from Cheltenham Beach, Devonport, c. 1908

From 1925 to 1936, prison labour built roads on the island and a track to the summit.[6] Islington Bay was formed in the southeast area of the island. Formerly known as Drunks Bay, it was used as a drying out area for inebriated crews before they ventured out of the gulf.[36] The bay is used by Auckland boat-owners as a refuge, as it is quite sheltered from the prevailing southwest winds.

Military installations were built during World War II to support the Auckland harbour defences and to house U.S. troops or store mines. The most visited remains of these installations is the old observation post on the summit. The northern shore of the island was used as a wrecking ground for unwanted ships, and the remains of several wrecks are still visible at low tide.[37][38] At least 13 ships were wrecked from 1887,[39] the last being the former Wellington[40] and, later, Waiheke ferry, Duchess,[41] in June 1947.[42] (built 1897[43] - iron deck framing remained in 2014). Other ships include Ngapuhi (1900 - her stern remained in 2014), Jubilee (1857), Arapawa (1908), Rothesay Bay (1877), Gladbrook (ex Countess of Anglesea 1877), Elinor Vernon (1876), Polly (ex Skovland 1891), Columbia (1899 - part of the keel and frame remained in 2014), Dartford (1877) and Rarawa (1903 - the bow, framing, iron plating and stern with two propeller shaft housings were visible above the low water mark in 2014).[44]

Baches (small holiday houses) were built around the island's edge in the 1920s and 1930s. The legality of their existence was doubtful from the start and the building of further baches was banned in 1937. Most have since been removed because of the ban and because the island has become a scenic reserve. However, 30 of the 140 baches remain as of 2010,[32] and some are being preserved to show how the island used to be, once boasting a permanent community of several hundred people, including many children. The buildings included some more permanent structures like a seawater pool built of quarried stones by convict labour, located close to the current ferry quay.[45]

Viewed from Mount Victoria. The island is close to the Auckland shore.

Access and tourism

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Regular ferry services and island tours by tractor-trailer are provided by Fullers from Auckland city centre.[46] A boardwalk with around 300 steps allows visitors to reach the summit and enjoy a view of the wooded crater. The distance to the summit is 2.4 km (1.5 mi), a one–hour walk by the most direct route.[47]

An alternative to walking, a land train, coordinated with the ferry sailings, takes visitors to a short way below the summit.[27] Sea kayak trips from the mainland to the island are also available.[48]

There are no campsites on the island, though there is camping at Home Bay on the adjacent Motutapu Island.[49]

See also

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References

[edit]
  1. ^ a b McGee L. 2020. U-Th-Ra analyses of samples from the 2016 drill core of the Rangitoto lava field: Devora report. GNS Science Report 2020/03, 8 p. |url=https://shop.gns.cri.nz/sr_2020-03-pdf/
  2. ^ "Auckland Volcanic Field: Photo Gallery". Global Volcanism Program. Smithsonian Institution. Retrieved 21 June 2008.
  3. ^ a b "Auckland Field". Global Volcanism Program. Smithsonian Institution. Retrieved 29 April 2009.
  4. ^ a b c d e f Luthfian, Alutsyah; Eccles, Jennifer D.; Miller, Craig A. (2023). "Gravity and magnetic models at Rangitoto Volcano, Auckland Volcanic Field, New Zealand: Implications for basement control on magma ascent". Journal of Volcanology and Geothermal Research. 439 (107824). doi:10.1016/j.jvolgeores.2023.107824. hdl:2292/65385. ISSN 0377-0273.
  5. ^ Devora (2020). Rangitoto: Odd one out. The story of Auckland's largest volcano. Devora Fact Sheet 03."DEVORA Fact Sheet 3 - Rangitoto: Odd One Out". Retrieved 3 March 2023.
  6. ^ a b c d e Hauraki Gulf Islands – Rangitoto Island Archived 25 December 2010 at the Wayback Machine, Auckland City Council. Updated September 2008. Retrieved 29 April 2009.
  7. ^ Ottaway, Jacqueline Crompton (30 April 2004). "Rangitoto – Auckland's Fragile Icon". NZine. Retrieved 26 April 2010.
  8. ^ a b What happened to local Maori? Archived 5 October 2003 at the Wayback Machine (from the Rangitoto page on the GNS Science website)
  9. ^ a b c d e f g Rangitoto Archived 20 May 2008 at the Wayback Machine (from the Auckland Regional Council website)
  10. ^ a b c Rangitoto (abridged article from New Zealand National Geographic)
  11. ^ a b Needham, A.J., Lindsay, J.M., Smith, I.E.M., Augustinus, P., Shane, P.A.L., 2011. Sequential eruption of alkaline and sub-alkaline magmas from a small monogenetic volcano in the Auckland Volcanic Field, New Zealand. Journal of Volcanology and Geothermal Research 201, 126-142. doi=10.1016/j.jvolgeores.2010.07.017
  12. ^ Shane, P.; Gehrels, M.; Zawalna-Geer, A.; Augustinus, P.A.; Lindsay, J.M.; Chaillou, I. (2013). "Longevity of a small shield volcano revealed by crypto-tephra studies (Rangitoto volcano, New Zealand): Change in eruptive behavior of a basaltic field". Journal of Volcanology and Geothermal Research. 257: 174–183. doi:10.1016/j.jvolgeores.2013.03.026.
  13. ^ Shane, Phil; Linnell, Tamzin (March 2015). "Reconstructing Rangitoto volcano from a 150-m-deep drill core (project 14/U684)" (PDF). University of Auckland. Retrieved 6 October 2015.
  14. ^ a b Linnell, Tamzin; et al. (2016). "Long-lived shield volcanism within a monogenetic basaltic field: The conundrum of Rangitoto volcano, New Zealand". Geological Society of America Bulletin. 128 (7–8): 1160–1172. Bibcode:2016GSAB..128.1160L. doi:10.1130/B31392.1.
  15. ^ "Officials downplay volcano danger". 3 News NZ. 12 April 2013. Retrieved 9 April 2016.
  16. ^ Hayward, B.W.; Grenfell, H.R. 2013. Did Rangitoto erupt many times? Geoscience Society of New Zealand Newsletter 11: 5–8. url= https://www.researchgate.net/publication/258374103_Did_Rangitoto_erupt_many_times
  17. ^ Hayward, B.W. 2017. Eruption sequence of Rangitoto Volcano, Auckland. Geoscience Society of New Zealand Newsletter 23: 4–10. url=https://www.researchgate.net/publication/321062566_Eruption_sequence_of_Rangitoto_Volcano_Auckland%7C
  18. ^ Cronin S, Kanakiya S, Brenna M, Shane P, Smith I, Ukstins I, Horkley K. 2018. Rangitoto Volcano, Auckland city, a one-shot wonder or a continued volcanic threat? Paper presented at: DEVORA forum; Oct 25–26; Auckland, New Zealand. url=https://auckland.figshare.com/articles/media/DEVORA_Forum_2018_Collection/12725501
  19. ^ Grant-Mackie, J.A., Cook, S. de C., `1990. A Late Quaternary Anadara-bearing deposit disturbed by Rangitoto Lava. 17: 73–79. New Zealand Natural Sciences 17: 73-79 |url=https://sites.google.com/site/nznaturalsciences/new-zealand-natural-sciences-journal/archived-issues/volume-17-1990%7C
  20. ^ Hayward, Bruce W; Hopkins, Jenni L; Morley, Margaret; Kenny, Jill A (2022). "Microfossil evidence for a possible maar crater and tuff ring beneath Rangitoto Volcano, Auckland, New Zealand". New Zealand Journal of Geology and Geophysics: 1–17. doi:10.1080/00288306.2022.2120505. ISSN 0028-8306.
  21. ^ Crossley, P. 2014. Inside Auckland lava caves. New Zealand Speleological Bulletin vol. 11, no. 208, p. 202-206.
  22. ^ Julian, Andrea (1992). The vegetation pattern of Rangitoto (PhD thesis). University of Auckland. hdl:2292/27.
  23. ^ a b Nichol, Reg (September 1992). "The eruption history of Rangitoto: reappraisal of a small New Zealand myth". Journal of the Royal Society of New Zealand. 22 (3): 159–180 [170]. doi:10.1080/03036758.1992.10426554.
  24. ^ Spurr, Eric B.; Anderson, Sandra H. (2004). "Bird species diversity and abundance before and after eradication of possums and wallabies on Rangitoto Island, Hauraki Gulf, New Zealand". New Zealand Journal of Ecology. 28 (1): 143–149. Retrieved 30 March 2020.
  25. ^ Mike D Wilcox; et al. (2007). Natural History of Rangitoto Island. Auckland Botanical Society. pp. 23–24. ISBN 978-0-9583447-3-9.
  26. ^ Rangitoto & Motutapu restoration project, Department of Conservation.
  27. ^ a b Rangitoto Island – Unique Volcanic Island (from the Fullers ferry operator website)
  28. ^ Mike D Wilcox; et al. (2007). Natural History of Rangitoto Island. Auckland Botanical Society. p. 16. ISBN 978-0-9583447-3-9.
  29. ^ a b Cameron, Ewen; Hayward, Bruce; Murdoch, Graeme (2008). A Field Guide to Auckland: Exploring the Region's Natural and Historical Heritage (Revised ed.). Random House New Zealand. pp. 282–283. ISBN 978-1-86962-1513.
  30. ^ Māngere-Ōtāhuhu Area Plan Update (PDF) (Report). Māngere-Ōtāhuhu Local Board, Auckland Council. September 2022. Retrieved 1 May 2023.
  31. ^ Taonui, Rāwiri (10 February 2015). "Tāmaki tribes". Te Ara: The Encyclopedia of New Zealand. Ministry for Culture and Heritage. Retrieved 15 September 2016.
  32. ^ a b c "The Hauraki Gulf Marine Park, Part 2". Inset to The New Zealand Herald. 2 March 2010.
  33. ^ Gordon Ell (1980). Rangitoto. Bush Jacket Guides. Auckland: The Bush Press. ISBN 978-0-908608-04-1.
  34. ^ Wolfe, R. (2002). Auckland: a pictorial history. Auckland: Random House. p 228.
  35. ^ Glenys Robertson (2005). Exploring North Island Volcanoes. Auckland: New Holland Publishers. p. 126. ISBN 978-1-86966-078-9.
  36. ^ Gray, Matthew (23 March 2010). "Drunks Bay proves a fateful spot". Stuff. Retrieved 30 March 2020.
  37. ^ "Rangitoto Ships' Graveyard". Auckland Regional Council website. Retrieved 8 June 2008.
  38. ^ Bennett, Kurt. Rich Pickings: Abandoned Vessel Material Reuse on Rangitoto Island, New Zealand (Thesis). Flinders University website. Retrieved 6 February 2016.
  39. ^ "Shipwrecks on Rangitoto". www.rangitoto.org. Retrieved 18 July 2019.
  40. ^ "New Zealand Maritime Index". www.nzmaritimeindex.org.nz. Retrieved 18 July 2019.
  41. ^ "Waiheke residents come to town NEW ZEALAND HERALD". paperspast.natlib.govt.nz. 9 January 1932. Retrieved 18 July 2019.
  42. ^ "1931 – Duchess – Discover – STQRY". discover.stqry.com. Retrieved 18 July 2019.
  43. ^ "Screw Steamer DUCHESS built by Mackie & Thomson in 1897 for J. H. Williams. Wellington Harbour Ferries Ltd., Ferry". www.clydeships.co.uk. Retrieved 22 January 2024.
  44. ^ Bennett, Kurt (2014). "Rich Pickings". Academia.
  45. ^ Welcome to Rangitoto Island (from the Rangitoto Island Historic Conservation Trust)
  46. ^ "Rangitoto Island". Fullers Group. Retrieved 31 May 2019.
  47. ^ McCormack, Michael (January 2019). "Active and Well in Nature with a Green Prescription: Rangitoto Island, NZ" (PDF). Activity and Nutrition Aotearoa.
  48. ^ Kayak Trips to Rangitoto Archived 10 November 2012 at the Wayback Machine (Day Trips to Rangitoto Island)
  49. ^ "Home Bay, Motutapu Island Campsite". www.doc.govt.nz. Department of Conservation. Retrieved 30 March 2020.

Further reading

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Wikimedia Commons has media related to Rangitoto Island.

36°47′12″S 174°51′36″E / 36.786742°S 174.860115°E / -36.786742; 174.860115

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