Earth:Poor Knights Islands

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Short description: Group of islands and marine reserve off the east coast of New Zealand's North Island


Poor Knights Islands
Tawhiti Rahi (Māori)
Geography
LocationNorthland, New Zealand
Coordinates [ ⚑ ] 35°30′S 174°45′E / 35.5°S 174.75°E / -35.5; 174.75
Area2.714[1] km2 (1.048 sq mi)
Administration
New Zealand
Designated1975
Poor Knights lily (Xeronema callistemon) plants growing in situ
Flowering Poor Knights lily in cultivation
Buller's shearwater on sea surface
Large numbers of Buller's shearwaters breed on the islands
The waters off the Poor Knights are a marine reserve with subtropical species

The Poor Knights Islands (Māori: Tawhiti Rahi) are a group of islands off the east coast of the Northland Region of the North Island of New Zealand. They lie 50 kilometres (31 mi) to the northeast of Whangārei, and 22 kilometres (14 mi) offshore halfway between Bream Head and Cape Brett. Uninhabited since the 1820s, they are a nature reserve and popular underwater diving spot, with boat tours typically departing from Tutukaka. The Poor Knights Islands Marine Reserve surrounds the island.

Beaglehole (1955) comments that the origin of the island name is not clear, and speculates that the name could be related to the Poor Knights of Windsor, or that the islands were named for their resemblance to Poor Knight's Pudding, a bread-based dish topped with egg and fried, popular at the time of discovery by Europeans.

Description

The chain consists of two large islands (Tawhiti Rahi, the larger at 151.5 ha (374 acres), and Aorangi (101 ha (250 acres)) to the south),[2] and several smaller islands. Aorangaia and Archway Island lie to the southwest of Aorangi Island, and there is also a group of smaller rocky islets between the two main islands, the largest of which is Motu Kapiti Island. Others include Bird and Kaka Rock. To the south, there is a smaller island named Ngoio Rock. The Poor Knights Islands are the eroded remnants of a 4-million-year-old rhyolitic volcano that is estimated to have been 1,000 metres (3,300 ft) tall and 25 kilometres (16 mi) in diameter.[3]

Oceanography

Spring tide range for the islands is around 2 m (6.56 ft), decreasing to a neap tide of around 1 m (3.28 ft). The deep water around the island results in only moderate tidal currents. These are around the same magnitude as the prevailing shelf currents. In the general vicinity of the islands mean flows are around 0.2 m/s (0.656 ft/s) and run toward the southeast.[4]

A remarkable feature of the region is the large internal tides that occur. These are a form of internal wave driven by the local tidal flow forcing the stratification against sloping areas of the shelf face. The surface manifestation of these waves can be seen from space.[5] These waves generate brief highly localised accelerations. Internal wave amplitudes of around 100 m (109 yd) have been observed, generating flow speeds as great as 0.5 m/s (1.64 ft/s).[6]

Geology

The Poor Knights Islands were created in some of the earliest eruptions of the Coromandel Volcanic Zone, between 10 and 9.5 million years ago. The Poor Knights Islands vulcanism represents an early period for the Coromandel Volcanic Zone, as changes in tectonic forces caused the east belt of the Northland Arc (23 to 16 million years ago) to begin moving southwards, and eventually forming the modern Taupō Volcanic Zone.[7]

Environment

The islands are protected as a nature reserve and a permit is required to land or tie boats up. Permits are usually granted only for scientific research. A notable native plant of the islands is the spectacularly flowering Poor Knights lily, which has become a popular garden plant.

Feral pigs, which had roamed Aorangi since the departure of Māori in the 1820s, were exterminated in 1936.[8] The islands have been identified as an Important Bird Area, by BirdLife International because they are home to a breeding population of about 200,000 pairs of Buller's shearwaters.[9]

The islands contain rock arches and sea caves, including Rikoriko Cave, the largest cave in the world by volume, with a cavern measuring 221,494 cubic metres (7,822,000 cu ft) and an opening large enough for small tour boats to enter.[10][11] Rikoriko Cave measures 130 by 80 metres (430 by 260 ft), with a ceiling height of 35 metres (115 ft) and extends 26 metres (85 ft) deep below water.[3]

Tawhiti Rahi contains the Northern Arch, Middle Arch, and Maomao Arch, the latter being a popular diving location. Aorangaia Island's east–west rock arch resembles a long tunnel, while the aptly named Archway Island is bisected by two rock arches, with the larger Cathedral Arch about 40 metres (130 ft) tall.[12]

History

The islands were earlier inhabited by Māori of the Ngāti Wai tribe who grew crops and fished the surrounding sea. The tribe traded with other Maori.

A chief of the tribe named Tatua led his warriors on a fighting expedition to the Hauraki Gulf with Ngā Puhi chief Hongi Hika in the early 1820s. While they were away, a slave named Paha escaped the islands and travelled to Hokianga where he told Waikato, a chief of the Hikutu tribe, that the islands had been left undefended. As Waikato had been offended by Tatua some years previous when he was refused pigs he had come to trade for, so he and his warriors set out on three large canoes to attack the islands. They arrived at the islands one night in December 1823[13] and soon overpowered the islanders in the absence of their warriors. Many islanders jumped off the high cliffs to avoid being taken as slaves. Tatua's wife Oneho and daughter were captured and taken to the mainland where a distant relative recognised the wife and helped the two to escape.

Tatua returned to the islands to find a scene of destruction. Only nine or ten people were left on the islands, including his five-year-old son Wehiwehi who had been hidden in a cave during the attack. The islands were declared tapu and Tatua left with the survivors and went to Rawhiti in the Bay of Islands where he unexpectedly found his wife and daughter.[14][15][16][17]

See also

  • List of volcanoes in New Zealand
  • List of islands of New Zealand
  • List of islands
  • Desert island

References

  1. ↑ "Data Table – Protected Areas – LINZ Data Service (recorded area 271.4 ha, incl. Sugarloaf Rock and High Peak Rocks)". Land Information New Zealand. https://data.linz.govt.nz/layer/53564-protected-areas/data/90474/. 
  2. ↑ West, Carol J. (1999). Poor Knights Islands weed control programme, Conservation Advisory Science Notes No. 233, Department of Conservation, Wellington.
  3. ↑ 3.0 3.1 "The World's Largest Sea Cave". Tourism New Zealand. https://www.newzealand.com/int/article/worlds-largest-sea-cave/. 
  4. ↑ Sharples, J.; Greig, M. J. N. (1998). "Tidal currents, mean flows, and upwelling on the north-east shelf of New Zealand". N. Z. J. Mar. Freshwater Res. 32 (2): 215–231. doi:10.1080/00288330.1998.9516821. http://www.royalsociety.org.nz/Site/publish/Journals/nzjmfr/1998/20.aspx. 
  5. ↑ Sharples (2001). "Internal tide dissipation, mixing, and vertical nitrate flux at the shelf edge on NE New Zealand". J. Geophys. Res. 106 (C7): 14069–14081. doi:10.1029/2000jc000604. Bibcode: 2001JGR...10614069S. 
  6. ↑ Stevens, C.L.; Abraham, E.R.; Moore, C.M.; Boyd, P.W.; Sharples, J. (2005). "Observations of Small-Scale Processes Associated with the Internal Tide Encountering an Island". J. Phys. Oceanogr. 35 (9): 1553–1567. doi:10.1175/JPO2754.1. Bibcode: 2005JPO....35.1553S. 
  7. ↑ Hayward, Bruce W. (2017). Out of the Ocean, Into the Fire. Geoscience Society of New Zealand. pp. 134–147. ISBN 978-0-473-39596-4. 
  8. ↑ Cranwell, L.M.; Moore, L.B. (1938). "Intertidal Communities of the Poor Knights Islands, New Zealand". Transactions and Proceedings of the Royal Society of New Zealand 67. http://rsnz.natlib.govt.nz/volume/rsnz_67/rsnz_67_04_003750.html. 
  9. ↑ BirdLife International. (2012). Important Bird Areas factsheet: Poor Knights Islands. Downloaded from http://www.birdlife.org on 4 February 2012.
  10. ↑ Bunnell, D. (May 2004). "Riko Riko Cave, New Zealand-World's Largest Sea Cave ?". NSS News 62 (5): 145–147. 
  11. ↑ "Poor Knights Island Marine Reserve". Department of Conservation. p. 2. https://www.doc.govt.nz/Documents/about-doc/concessions-and-permits/conservation-revealed/poor-knights-island-marine-reserv-lowres.pdf. 
  12. ↑ Bruce W Hayward. "Geology and geomorphology of the Poor Knights Islands". Auckland Institute and Museum. pp. 34–36. http://www.thebookshelf.auckland.ac.nz/docs/Tane/Tane-33/5%20Geology%20and%20geomorphology.pdf. 
  13. ↑ Borley, Craig (27 May 2008). "'Maori Pompeii' yields treasures". The New Zealand Herald. http://www.nzherald.co.nz/human-science/news/article.cfm?c_id=314&objectid=10512676. 
  14. ↑ "Poor Knights Islands Marine Reserve ", Department of Conservation, New Zealand.
  15. ↑ The Poor Knights and The Poor Squires (The Pinnacles) Geology . Whangarei Deep Sea Anglers Club. Retrieved 31 May 2008.
  16. ↑ "Whakapapa", The Patuone Website.
  17. ↑ "Pre-European history – Dive! Tutukaka". https://diving.co.nz/poor-knights-islands/about-the-islands/pre-european-history. 

External links

  • "Geology – New Zealand's Geological History", from An Encyclopaedia of New Zealand, edited by A. H. McLintock, originally published in 1966. Te Ara – The Encyclopedia of New Zealand, updated 2006-09-26. Retrieved 2007-04-15.


[ ⚑ ] 35°30′S 174°45′E / 35.5°S 174.75°E / -35.5; 174.75



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