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Tasmantis and biogeography
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{{ otheruses4|the continent|the ship|Zealandia }}
{{ otheruses4|the continent|the ship|Zealandia }}


'''Zealandia''' ({{IPAEng|ziːˈlæːndiə}}), also known as the '''New Zealand continent''', is a nearly submerged [[continent]] that sank after breaking away from [[Australia]] 60-85 million years ago<ref name="Te Ara">{{cite web |author=Keith Lewis |coauthors= Scott D. Nodder and Lionel Carter |url=http://www.teara.govt.nz/EarthSeaAndSky/OceanStudyAndConservation/SeaFloorGeology/1/en | title=Zealandia: the New Zealand continent |work=Te Ara - the Encyclopedia of New Zealand |date=[[2007-01-11]] | accessdate=2007-02-22}}</ref> and from [[Antarctica]] between 130 and 85 million years ago. It may have been completely submerged about 23 million years ago,<ref>{{cite news |title=Searching for the lost continent of Zealandia |url=http://www.stuff.co.nz/4219871a11.html?source=RSSnationalnews_20070929 |work= |publisher=The [[Dominion Post]] |date=29 September 2007 |accessdate=2007-10-09 |quote=We cannot categorically say that there has always been land here. The geological evidence at present is too weak, so we are logically forced to consider the possibility that the whole of Zealandia may have sunk.}}</ref> and most of it (93%) remains submerged under the [[Pacific Ocean]].
'''Zealandia''' ({{IPAEng|ziːˈlæːndiə}}), also known as '''Tasmantis''' or the '''New Zealand continent''', is a nearly submerged [[continent]] that sank after breaking away from [[Australia]] 60-85 million years ago<ref name="Te Ara">{{cite web |author=Keith Lewis |coauthors= Scott D. Nodder and Lionel Carter |url=http://www.teara.govt.nz/EarthSeaAndSky/OceanStudyAndConservation/SeaFloorGeology/1/en | title=Zealandia: the New Zealand continent |work=Te Ara - the Encyclopedia of New Zealand |date=[[2007-01-11]] | accessdate=2007-02-22}}</ref> and from [[Antarctica]] between 130 and 85 million years ago. It may have been completely submerged about 23 million years ago,<ref>{{cite news |title=Searching for the lost continent of Zealandia |url=http://www.stuff.co.nz/4219871a11.html?source=RSSnationalnews_20070929 |work= |publisher=The [[Dominion Post]] |date=29 September 2007 |accessdate=2007-10-09 |quote=We cannot categorically say that there has always been land here. The geological evidence at present is too weak, so we are logically forced to consider the possibility that the whole of Zealandia may have sunk.}}</ref> and most of it (93%) remains submerged under the [[Pacific Ocean]].


Zealandia is 3,500,000 [[1 E12 m²|km²]] in area; this is larger than [[Greenland]] or [[India]], and almost half the size of Australia. It is unusually long and narrow, stretching from [[New Caledonia]] in the north to beyond [[New Zealand sub-antarctic islands|New Zealand's sub-antarctic islands]] in the south (from latitude 19° south to 56° south,<ref name="Te Ara"/> analogous to ranging from [[Haiti]] to [[Hudson Bay]] or from [[Sudan]] to [[Sweden]] in the northern hemisphere). [[New Zealand]] is the largest part of Zealandia that is above [[sea level]], followed by [[New Caledonia]].
Zealandia is 3,500,000 [[1 E12 m²|km²]] in area; this is larger than [[Greenland]] or [[India]], and almost half the size of Australia. It is unusually long and narrow, stretching from [[New Caledonia]] in the north to beyond [[New Zealand sub-antarctic islands|New Zealand's sub-antarctic islands]] in the south (from latitude 19° south to 56° south,<ref name="Te Ara"/> analogous to ranging from [[Haiti]] to [[Hudson Bay]] or from [[Sudan]] to [[Sweden]] in the northern hemisphere). [[New Zealand]] is the largest part of Zealandia that is above [[sea level]], followed by [[New Caledonia]].
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Volcanism on Zealandia has also taken place repeatedly in various parts of the continent before, during and after it [[rift]]ed away from the [[supercontinent]] [[Gondwana]]. Although Zealandia has shifted ~6000 km to the northwest and respect to the underlying [[mantle (geology)|mantle]] from the time when it rifted from Antarctica, recurring intracontinental volcanism exhibits similar magma composition to volcanoes in previously adjacent parts of Antarctica and Australia. This volcanism is widespread across Zealandia but generally of low volume apart from the huge mid to late [[Miocene]] [[shield volcano]]es developing the [[Banks Peninsula|Bank]]s and [[Otago Peninsula]]s. In addition, it took place continually in numerous limited regions all through the [[Late Cretaceous]] and the [[Cenozoic]]. However, its causes are still in dispute. During the [[Miocene]], the northern section of Zealandia ([[Lord Howe Rise]]) might have slid over a stationary [[hotspot (geology)|hotspot]], forming the [[Lord Howe seamount chain]].
Volcanism on Zealandia has also taken place repeatedly in various parts of the continent before, during and after it [[rift]]ed away from the [[supercontinent]] [[Gondwana]]. Although Zealandia has shifted ~6000 km to the northwest and respect to the underlying [[mantle (geology)|mantle]] from the time when it rifted from Antarctica, recurring intracontinental volcanism exhibits similar magma composition to volcanoes in previously adjacent parts of Antarctica and Australia. This volcanism is widespread across Zealandia but generally of low volume apart from the huge mid to late [[Miocene]] [[shield volcano]]es developing the [[Banks Peninsula|Bank]]s and [[Otago Peninsula]]s. In addition, it took place continually in numerous limited regions all through the [[Late Cretaceous]] and the [[Cenozoic]]. However, its causes are still in dispute. During the [[Miocene]], the northern section of Zealandia ([[Lord Howe Rise]]) might have slid over a stationary [[hotspot (geology)|hotspot]], forming the [[Lord Howe seamount chain]].

==Biogeography==

New Caledonia and New Zealand, which lie at the northern and eastern ends, respectively, of the ancient continent. [[Lord Howe Island]] is of fairly recent volcanic origin. These land masses are two outposts of the [[Antarctic Flora]], including [[Araucaria]]s and [[Podocarp]]s. The islands have no native land [[mammal]] fauna. <ref>Flannery, Tim (1994). ''The Future Eaters''. Grove Press, New York. Pages 42-43.</ref>



==References==
==References==

Revision as of 18:57, 19 October 2007

Topography of Zealandia. The linear ridges running NNE and SW away from New Zealand are not considered part of the continent, nor are Australia (upper left), Fiji or Vanuatu (top centre).[1]
This article is about the continent. For the ship, see Zealandia.

Zealandia (/ziːˈlæːndiə/), also known as Tasmantis or the New Zealand continent, is a nearly submerged continent that sank after breaking away from Australia 60-85 million years ago[2] and from Antarctica between 130 and 85 million years ago. It may have been completely submerged about 23 million years ago,[3] and most of it (93%) remains submerged under the Pacific Ocean.

Zealandia is 3,500,000 km² in area; this is larger than Greenland or India, and almost half the size of Australia. It is unusually long and narrow, stretching from New Caledonia in the north to beyond New Zealand's sub-antarctic islands in the south (from latitude 19° south to 56° south,[2] analogous to ranging from Haiti to Hudson Bay or from Sudan to Sweden in the northern hemisphere). New Zealand is the largest part of Zealandia that is above sea level, followed by New Caledonia.

The major submerged parts of Zealandia are the Lord Howe Rise, Challenger Plateau, Campbell Plateau, Norfolk Ridge, Hikurangi Plateau and the Chatham Rise. Smaller provinces include the Louisiade Plateau, Mellish Rise, Kenn Plateau, Chesterfield Plateau, and Dampier Ridge.[4] The seemingly separate Gilbert Seamount (northwest of Fiordland) is also part of the New Zealand continent,[5] while how strongly Bollons Seamount (south of the Chatham Islands) remains connected to Zealandia is unknown.

Zealandia supports substantial inshore fisheries and contains New Zealand's largest gas field. Some parts of Zealandia may be mined in the future.

Geology

Unlike most continents, Zealandia is largely made up of two nearly parallel ridges. The ridges develop sea floor 1,000-1,500 meters deep, with infrequent rocky islands rising above sea level. The ridges are continental rock, but are deeper than normal continents because their crust is thinner than usual (only about 20 kilometers thick), and consequently drift lower on the earth's mantle.

About 25 million years ago, the southern part of Zealandia (on the Pacific Plate) began to shift relative to the northern part (on the Indo-Australian Plate). The resulting displacement by approximately 500 kilometres (300 mi) along the Alpine Fault is evident in geological maps.[6] Compression across the plate boundary has uplifted the Southern Alps. Further north, subduction of the Pacific Plate has led to extensive volcanism, including the Coromandel and Taupo Volcanic Zones.

Volcanism on Zealandia has also taken place repeatedly in various parts of the continent before, during and after it rifted away from the supercontinent Gondwana. Although Zealandia has shifted ~6000 km to the northwest and respect to the underlying mantle from the time when it rifted from Antarctica, recurring intracontinental volcanism exhibits similar magma composition to volcanoes in previously adjacent parts of Antarctica and Australia. This volcanism is widespread across Zealandia but generally of low volume apart from the huge mid to late Miocene shield volcanoes developing the Banks and Otago Peninsulas. In addition, it took place continually in numerous limited regions all through the Late Cretaceous and the Cenozoic. However, its causes are still in dispute. During the Miocene, the northern section of Zealandia (Lord Howe Rise) might have slid over a stationary hotspot, forming the Lord Howe seamount chain.

Biogeography

New Caledonia and New Zealand, which lie at the northern and eastern ends, respectively, of the ancient continent. Lord Howe Island is of fairly recent volcanic origin. These land masses are two outposts of the Antarctic Flora, including Araucarias and Podocarps. The islands have no native land mammal fauna. [7]


References

  1. ^ "Figure 8.1: New Zealand in relation to the Indo-Australian and Pacific Plates". The State of New Zealand’s Environment 1997. 1997. Retrieved 2007-04-20.
  2. ^ a b Keith Lewis (2007-01-11). "Zealandia: the New Zealand continent". Te Ara - the Encyclopedia of New Zealand. Retrieved 2007-02-22. {{cite web}}: Check date values in: |date= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  3. ^ "Searching for the lost continent of Zealandia". The Dominion Post. 29 September 2007. Retrieved 2007-10-09. We cannot categorically say that there has always been land here. The geological evidence at present is too weak, so we are logically forced to consider the possibility that the whole of Zealandia may have sunk.
  4. ^ Mortimer, Nick (2006), "Zealandia" (PDF), Australian Earth Sciences Convention, Melbourne, Australia, p. 4, retrieved 2007-03-28{{citation}}: CS1 maint: location missing publisher (link).
  5. ^ Wood, Ray (2003). New Zealand's Continental Shelf and UNCLOS Article 76 (PDF). Institute of Geological and Nuclear Sciences series 56; NIWA technical report 123. Wellington, New Zealand: Institute of Geological and Nuclear Sciences Limited; National Institute of Water and Atmospheric Research. p. 16. Retrieved 2007-02-22. The continuous rifted basement structure, thickness of the crust, and lack of seafloor spreading anomalies are evidence of prolongation of the New Zealand land mass to Gilbert Seamount. {{cite book}}: Cite has empty unknown parameters: |origmonth= and |origdate= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  6. ^ "Figure 4. Basement rocks of New Zealand". UNCLOS Article 76: The Land mass, continental shelf, and deep ocean floor: Accretion and suturing. Retrieved 2007-04-21.
  7. ^ Flannery, Tim (1994). The Future Eaters. Grove Press, New York. Pages 42-43.

External links

Retrieved from "https://en.wikipedia.org/w/index.php?title=Zealandia&oldid=165684663"