Auckland volcanic field

The Auckland volcanic field is an area of monogenetic volcanoes covered by much of the metropolitan area of Auckland, New Zealand's largest city, located in the North Island. The approximately 53 volcanoes[1] in the field have produced a diverse array of maars (explosion craters), tuff rings, scoria cones, and lava flows. No volcano has erupted twice, but eruptions lasted for various periods ranging from a few weeks to several years.[2] The field is fuelled entirely by basaltic magma, unlike the explosive subduction-driven volcanism in the central North Island, such as at Mount Ruapehu and Lake Taupo.[3] The field is currently dormant, but could become active again.[4]

Auckland Volcanic Field
Map of the Auckland Volcanic Field from 1859
Map of the field drawn by Hochstetter in 1859 and published in English in 1864
Highest point
Elevation260 m (850 ft)
Coordinates36°52′37″S 174°45′50″E / 36.877°S 174.764°E / -36.877; 174.764Coordinates: 36°52′37″S 174°45′50″E / 36.877°S 174.764°E / -36.877; 174.764
Geology
Age of rockPleistocene and Holocene
Mountain typeVolcanic Field
Type of rockBasalt
Last eruptionc. 1400 CE

FeaturesEdit

The field ranges from Lake Pupuke and Rangitoto Island in the north to Matukutururu (Wiri Mountain) in the south, and from Mount Albert in the west to Pigeon Mountain in the east.

The first vent erupted at Onepoto 248,000 ± 28,000 years ago.[5] The most recent eruption (about 600 years ago[6] and within historical memory of the local Māori iwi) was of Rangitoto, an island shield volcano just east of the city, erupting 2.3 cubic kilometres of lava. The last volcano to erupt was much bigger than all others, with Rangitoto making up almost 60 per cent of the field's entire volume of erupted material. The field's volcanoes are relatively small, with most less than 150 metres (490 ft) in height.

Lake Pupuke, on the North Shore near Takapuna, is a volcanic explosion crater. A few similar craters such as Orakei Basin are open to the sea.

The field has produced voluminous lava flows that cover much of the Auckland isthmus. One of the longest runs from Mt Saint John northward, almost crossing the Waitematā Harbour to form Meola Reef.[7] More than 50 lava tubes and other lava caves have been discovered, including the 290-metre (950 ft)-long Wiri Lava Cave.[8] The second-longest individual cave in the Auckland field, some 270 metres (890 ft) in total length, is the Cave of a Thousand Press-ups to the east of Maungakiekie/One Tree Hill.[9] Two impressive depressions caused by lava cave collapses are the Puka Street Grotto and the nearby Hochstetter Pond, also known as Grotto Street Pond, in Onehunga.[10][11]

For most of the 200,000 years that the field has been erupting, the planet has been in glacial periods (ice ages) where sea levels were much lower due to water being locked up as ice, and the Waitemata and Manukau Harbours were dry land. All the volcanoes probably erupted on land except for Rangitoto, which erupted during the current interglacial (warmer) period.[12]

Human contextEdit

 
Terraces carved by Māori into the slopes of One Tree Hill

UsageEdit

Many of the volcanic cones were occupied by substantial Māori before European settlement, and many terraces and other archeological remnants are still visible. Many of the cones have been levelled or strongly altered—in small part due to the historical Māori use, but mostly through relatively recent quarrying of construction materials (especially scoria). However several of the remaining volcanoes are now preserved as landmarks and parks.[6] The cones are also protected by a 1915 law, the Reserves and Other Lands Disposal and Public Bodies Empowering Act 1915, which was passed due to early concern that the distinctive landscape was being eroded, especially by quarrying. While often ignored until the late 20th century, it has amongst other things minimised severe changes to Mount Roskill proposed by Transit New Zealand for the Southwestern Motorway.[13]

In March 2007, New Zealand submitted the volcanic field, with several specifically named features, as a World Heritage Site candidate based on its unique combination of natural and cultural features.[6] At that time, only 2 per cent of more than 800 World Heritage Sites worldwide were in this "mixed" category.

DangersEdit

Since the field is not extinct, new volcanic events may occur at any time, though the usual period between events is, on average, somewhere between hundreds to thousands of years. However, the effects of such an event—especially a full-scale eruption—would be substantial, ranging from pyroclastic surges to earthquakes,[14] lava bombs, ash falls, and the venting volcanic gas, as well as lava flows. These effects might continue for several months, potentially causing substantial destruction and disruption, ranging from the burial of substantial tracts of residential or commercial property, to the mid-to-long-term closures of major parts of the country's infrastructure such as the Port of Auckland, the State Highway network, or the Auckland Airport.[4] It is possible that several volcanoes could erupt simultaneously. There is strong evidence that eight erupted within a span of 3000 years or so, between 31,000 and 28,000 years ago.

Various operative structures, plans and systems have been set up to prepare responses to volcanic activity within the urban areas, mainly coordinated in the 'Auckland Volcanic Field Contingency Plan' of the Auckland Regional Council, which provides a framework for interaction of civil defence and emergency services during an eruption. Auckland also has a seismic monitoring network comprising six seismometers—including one 250 metres (820 ft) deep at Riverhead—and three repeaters within the region that will detect the small tremors likely to precede any volcanic activity.[15] This is likely to give between a few hours and several days' warning of an impending eruption, and its approximate location.[14]

Auckland War Memorial Museum, itself built on the crater rim of Pukekawa, has an exhibition on the field, including the "Puia Street multi-sensory visitor experience", which simulates a grandstand view of an eruption in Auckland.[16]

In 2013, scientists said new studies showed 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 550 years ago.[17] Civil Defence officials said the discovery did not make living in Auckland any more dangerous, but did change their view of how an evacuation might proceed.[18]

List of volcanoesEdit

The volcanoes within the field are:[2][19][20]

Volcanoes Age Height Location (Coordinates) Refs Images
Albert Park Volcano ~145,000 years old Unclear 36°51′03″S 174°46′03″E / 36.8507°S 174.7675°E / -36.8507; 174.7675 [21]
Ash Hill 30,500 years old 30 metres (98 ft) 37°00′10″S 174°52′03″E / 37.002754°S 174.867545°E / -37.002754; 174.867545
Boggust Park Crater 130,000+ years old 5 metres (16 ft) 36°57′19″S 174°48′49″E / 36.955413°S 174.813552°E / -36.955413; 174.813552 [1]
Cemetery Crater Unknown 33 metres (108 ft) 36°59′23″S 174°50′28″E / 36.989828°S 174.841082°E / -36.989828; 174.841082 [1]
Crater Hill 30,500 years old 36°59′12″S 174°49′38″E / 36.986546°S 174.827135°E / -36.986546; 174.827135
Grafton Volcano 100,000 years old 36°51′30″S 174°45′49″E / 36.858440°S 174.763624°E / -36.858440; 174.763624
Hampton Park Unknown 35 metres (115 ft) 36°57′03″S 174°53′44″E / 36.950925°S 174.89544°E / -36.950925; 174.89544
Kohuora 30,500 years old 36°58′43″S 174°50′34″E / 36.97873°S 174.842691°E / -36.97873; 174.842691
Mangere Lagoon 50,000 years old 36°57′25″S 174°46′39″E / 36.95702°S 174.77763°E / -36.95702; 174.77763
Matanginui/Green Mount 20,000 years old 78 metres (256 ft) 36°56′24″S 174°53′54″E / 36.939911°S 174.898267°E / -36.939911; 174.898267
Matukutureia/McLaughlins Mountain 50,000 years old 73 metres (240 ft) 37°00′49″S 174°50′46″E / 37.013511°S 174.845974°E / -37.013511; 174.845974
Maungakiekie/One Tree Hill 60,000 years old 182 metres (597 ft) 36°54′0″S 174°46′59″E / 36.90000°S 174.78306°E / -36.90000; 174.78306
 
One Tree Hill and its obelisk
Maungarahiri/Little Rangitoto 24,500 years old 75 metres (246 ft) 36°52′31″S 174°48′35″E / 36.875407°S 174.809636°E / -36.875407; 174.809636
Maungarei/Mount Wellington 10,000 years old 135 metres (443 ft) 36°53′35″S 174°50′47.6″E / 36.89306°S 174.846556°E / -36.89306; 174.846556
Maungataketake/Elletts Mountain 90,000 years old 76 metres (249 ft) 36°59′41″S 174°44′51″E / 36.994635°S 174.747548°E / -36.994635; 174.747548
Maungauika/North Head 90,000 years old 50 metres (160 ft) 36°49′40″S 174°48′43″E / 36.827751°S 174.81205°E / -36.827751; 174.81205
Maungawhau/Mount Eden 28,000 years old 196 metres (643 ft) 36°52′37″S 174°45′50″E / 36.877°S 174.764°E / -36.877; 174.764
 
Crater of Maungawhau / Mount Eden
Motukorea/Browns Island 24,400 years old 68 metres (223 ft) 36°49′50″S 174°53′41″E / 36.8306°S 174.8948°E / -36.8306; 174.8948
Mount Robertson/Sturges Park 24,000 years old 78 metres (256 ft) 36°56′55″S 174°50′30″E / 36.948477°S 174.841726°E / -36.948477; 174.841726
Ōhinerau / Mount Hobson 34,000 years old 143 metres (469 ft) 36°52′40″S 174°47′10″E / 36.877814°S 174.786156°E / -36.877814; 174.786156
Ohuiarangi/Pigeon Mountain 24,500 years old 55 metres (180 ft) 36°53′20″S 174°54′11″E / 36.888846°S 174.903116°E / -36.888846; 174.903116
Orakei Basin 120,000 years old Sea level 36°52′02″S 174°48′47″E / 36.867124°S 174.81308°E / -36.867124; 174.81308
Otahuhu/Mount Richmond 30,000 years old 50 metres (160 ft) 36°55′57″S 174°50′22″E / 36.932562°S 174.839451°E / -36.932562; 174.839451
Ōtuataua 15,000 years old 64 metres (210 ft) 36°59′10″S 174°45′15″E / 36.98611°S 174.75417°E / -36.98611; 174.75417
Ōwairaka / Mount Albert 120,000 years old 135 metres (443 ft) 36°53′03″S 174°42′56″E / 36.8841°S 174.7156°E / -36.8841; 174.7156
Puhinui Craters 50,000 years old 22 metres (72 ft) 37°00′53″S 174°49′59″E / 37.01465°S 174.83296°E / -37.01465; 174.83296 [1]
Pukaki Lagoon 65,000 years old Sea Level 36°58′59″S 174°48′37″E / 36.982998°S 174.810226°E / -36.982998; 174.810226
Pukeiti 15,000 years old 30 metres (98 ft) 36°59′02″S 174°45′26″E / 36.983756°S 174.757183°E / -36.983756; 174.757183
Pukekawa/Auckland Domain 100,000 years old 36°51′33″S 174°46′33″E / 36.859158°S 174.775808°E / -36.859158; 174.775808
Puketāpapa / Mount Roskill 105,000 years old 110 metres (360 ft) 36°55′S 174°44′E / 36.917°S 174.733°E / -36.917; 174.733
Pukewairiki 130,000+ years old 30 metres (98 ft) 36°56′39″S 174°51′57″E / 36.944078°S 174.865887°E / -36.944078; 174.865887
Pupuke 190,000 years old −57 metres (−187 ft) 36°46′48″S 174°45′58″E / 36.780115°S 174.766184°E / -36.780115; 174.766184
Rangitoto Island 620-600 years old 260 metres (850 ft) 36°47′12″S 174°51′36″E / 36.786742°S 174.860115°E / -36.786742; 174.860115
 
Rangitoto Island on the horizon
Rarotonga / Mount Smart 20,000 years old 87 metres (285 ft) (quarried) 36°55′6″S 174°48′45″E / 36.91833°S 174.81250°E / -36.91833; 174.81250
Styaks Swamp 20,000 years old 36°56′10″S 174°54′01″E / 36.936138°S 174.900155°E / -36.936138; 174.900155
Takaroro / Mount Cambria 40,000 years old 30 metres (98 ft) (quarried) 36°49′28″S 174°48′07″E / 36.824444°S 174.801933°E / -36.824444; 174.801933
Takarunga / Mount Victoria 35,000 yrs old 87 metres (285 ft) 36°49′36″S 174°47′56″E / 36.8266°S 174.7990°E / -36.8266; 174.7990
Taurere / Taylors Hill 30,000 years old 56 metres (184 ft) 36°51′51″S 174°52′12″E / 36.864223°S 174.869943°E / -36.864223; 174.869943
Te Apunga-o-Tainui / McLennan Hills 41,000 years old 45 metres (148 ft) (quarried) 36°55′45″S 174°50′47″E / 36.929208°S 174.846468°E / -36.929208; 174.846468
Te Hopua-a-Rangi / Gloucester Park 20,000+ years old Sea level (reclaimed) 36°55′46″S 174°47′05″E / 36.9295°S 174.784734°E / -36.9295; 174.784734
Te Kopua Kai-a-Hiku / Panmure Basin 25,000 years old Sea level 36°54′18″S 174°50′58″E / 36.90495°S 174.849343°E / -36.90495; 174.849343
Te Kopua-o-Matakamokamo / Tank Farm 180,000 years old 36°48′07″S 174°45′12″E / 36.8020°S 174.7533°E / -36.8020; 174.7533
Onepoto 185,000 years old 36°48′29″S 174°45′03″E / 36.80818°S 174.75085°E / -36.80818; 174.75085
Te Kōpuke / Mount Saint John 75,000 years old 126 metres (413 ft) 36°53′00″S 174°46′49″E / 36.883431°S 174.780196°E / -36.883431; 174.780196
Te Motu-a-Hiaroa/Puketutu 30,000 years old 65 metres (213 ft) 36°57′55″S 174°44′50″E / 36.965186°S 174.747248°E / -36.965186; 174.747248
Te Pane-o-Mataaho/Māngere Mountain 50,000 years old 106 metres (348 ft) 36°56′59″S 174°46′59″E / 36.9496°S 174.7831°E / -36.9496; 174.7831 [22]
Te Pou Hawaiki 28,000 years old Quarried 36°52′57″S 174°46′00″E / 36.88247°S 174.766726°E / -36.88247; 174.766726
Te Puke ō Tara / Otara Hill Unknown 89 metres (292 ft) (quarried) 36°56′50″S 174°53′54″E / 36.947105°S 174.898363°E / -36.947105; 174.898363
Te Tātua-a-Riukiuta / Three Kings 28,500 years old 133 metres (436 ft) 36°54′11″S 174°45′17″E / 36.902926°S 174.754651°E / -36.902926; 174.754651
Te Tauoma / Purchas Hill 10,000 years old 50 metres (160 ft) (quarried) 36°53′14″S 174°50′51″E / 36.887138°S 174.847476°E / -36.887138; 174.847476
Waitomokia / Mt Gabriel 20,300 years old 20 metres (66 ft) (quarried) 36°58′37″S 174°46′13″E / 36.976981°S 174.770336°E / -36.976981; 174.770336
Whakamuhu/Saint Heliers/Glover Park – see Achilles Point 160,000 years old Sea level 36°50′36″S 174°51′50″E / 36.843390°S 174.863800°E / -36.843390; 174.863800
Wiri Mountain / Matukutūruru 30,000 years old 80 metres (260 ft) (quarried) 37°00′26″S 174°51′30″E / 37.007334°S 174.858441°E / -37.007334; 174.858441

See alsoEdit

ReferencesEdit

  1. ^ a b c d Hayward, Bruce W.; Kenny, Jill A.; Grenfell, Hugh R. (2011). "More volcanoes recognised in Auckland Volcanic Field" (PDF). Geoscience Society of New Zealand Newsletter (5): 11–16. Retrieved 19 April 2013.[permanent dead link]
  2. ^ a b Hayward, Bruce W.; Murdoch, Graeme; Maitland, Gordon (2011). Volcanoes of Auckland: The Essential Guide. Auckland University Press. ISBN 978-1-86940-479-6.
  3. ^ Ian E.M. Smith and Sharon R. Allen. Auckland volcanic field geology. Volcanic Hazards Working Group, Civil Defence Scientific Advisory Committee. Retrieved 30 March 2013. Also published in print as Volcanic hazards at the Auckland volcanic field. 1993.
  4. ^ a b Beca Carter Hollings & Ferner (2002). Contingency Plan for the Auckland Volcanic Field, Auckland Regional Council Technical Publication 165. Accessed 12 May 2008.
  5. ^ M.O. McWilliams research, 2002, associated with Shane P, Sandiford A (2003) Paleovegetation of marine isotope stages 4 and 3 in northern New Zealand and the age of the widespread Rotoehu Tephra. Quaternary Research 59:420–429
  6. ^ a b c Auckland Volcanic Fields submission (from the UNESCO World Heritage Centre, 30 March 2007. Accessed 4 May 2007)
  7. ^ Hayward, Murdoch, Maitland (2011). pp. 134–135.
  8. ^ David Lomas (Winter 2006). "Cave new world". Heritage New Zealand. Accessed 4 May 2007.
  9. ^ Kermode, Les (March 1994). "New Zealand lava caves worth preserving for their geologic and geomorphic features" (PDF). Geoscience Reports of Shizuoka University. 20: 15–24. Archived from the original (PDF) on 3 August 2016. Retrieved 6 December 2011.
  10. ^ Hayward, Murdoch, Maitland (2011). pp. 17–18.
  11. ^ "Geology". The Onehunga Grotto. Retrieved 25 April 2013.
  12. ^ Hayward, Murdoch, Maitland (2011). pp. 2–3.
  13. ^ "The volcanic hills are being destroyed..." – City of Fire, insert magazine in The New Zealand Herald, 15 February 2008
  14. ^ a b "When the earth starts to shake". City of Fire, insert magazine in The New Zealand Herald, 15 February 2008.
  15. ^ New recorder boosts earthquake, volcano warnings, The New Zealand Herald, NZPA, 11 May 2008. Accessed 12 May 2008.
  16. ^ "Volcanoes". Auckland War Memorial Museum. Retrieved 28 September 2017.
  17. ^ "Rangitoto more active than thought – study". 3 News NZ. 11 April 2013.
  18. ^ "Officials downplay volcano danger". 3 News NZ. 12 April 2013.
  19. ^ Lindsay, J.M.; Leonard, G.S.; Smid, E.R.; Hayward, B.W. (December 2011). "Age of the Auckland Volcanic Field: a review of existing data". New Zealand Journal of Geology and Geophysics. 54 (4): 379–401. doi:10.1080/00288306.2011.595805.
  20. ^ Hayward, B.W. (2019). Volcanoes of Auckland. A Field Guide. Auckland University Press. p. 334. ISBN 978-1-86940-901-2.
  21. ^ Searle, E. J. (May 1962). "The volcanoes of Auckland city". New Zealand Journal of Geology and Geophysics. 5 (2): 193–227. doi:10.1080/00288306.1962.10423108.
  22. ^ Mountain, Māngere. "Mangere Mountain History Formation | Mangere Mountain". Māngere Mountain. Retrieved 28 April 2019.

Further readingEdit

External linksEdit