Zealandia

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Zealandia
Location: in the south-western part of the Pacific Ocean , east to south-east of the continent of Australia
Coordinates northernmost point: 18 ° 30 'S, 158 ° 40'
E geocoordinates
Coordinates westernmost point: 23 ° 20 'S, 155 ° 10'
E geographic coordinates
Eastmost point coordinates: 42 ° 40 'S, 167 ° 45' W
geocoordinates
Coordinates southernmost point: 56 ° 10 'S, 164 ° 50'
E geographic coordinates
Surface: 4.9 million km²
North South expansion: around 4200 km
East-west extension (northern half): around 2800 km
East-west expansion (southern half): around 2350 km
Most of Zealandia is underwater. Ball's Pyramid is one of the places it rises above sea level.

Zealandia ( ziːˈlændiə ) is a largely submerged clod of highly expanded continental crust in the southwestern Pacific Ocean . The topographically highest and thus above sea level areas of this floe are the two main islands of New Zealand ( North Island and South Island ) as well as Stewart Island , the Chatham Islands , New Caledonia and a few smaller islands. In New Zealand, Zealandia is also known as New Zealand Continent .

Origin of name

The term Zealandia was first in 1995 by the American geologist Bruce P. Luyendyk from the University of California used the him as a collective term for New Zealand, the Chatham Rise ( rise .: English survey), the Campbell Plateau and the Lord Howe Rise used. He defined the term for a large region of contiguous continental crust, but not yet intended as a definition as a continent. More than 20 years have passed since then and scientific knowledge regarding the "underwater continent" has increased. In February 2017, a group of scientists (nine New Zealanders, one New Caledonian and one Australian) demanded that Zealandia be recognized as a continent in the March issue of GSA Today , a scientific journal of the Geological Society of America , and published their findings and arguments.

geography

According to the publication mentioned above, Zealandia extends over an area of ​​4.9 million square kilometers from New Caledonia with the Norfolk Ridge , the Kenn Plateau , the Lord Howe Rise and the Dampier Ridge in the north over the Challenger Plateau and New Zealand to the Campbell Plateau with the Islands Auckland Islands and Campbell Iceland in the south and the Chatham Rise to the Chatham Islands to the east. The apparently isolated Gilbert Seamount (northwest of Fiordland ) and the Bollons Seamount east of the Campbell Plateau also belonged to the continent. Of the continent outlined in this way, 94% are below sea level.

The largest subsea elevations include the Lord Howe Rise, Challenger Plateau, Campbell Plateau, Norfolk Ridge, and Chatham Rise. The two main islands of New Zealand (South Island: 3724 m, North Island: 2797 m) are among the highest elevations above water, followed by New Caledonia (1628 m) and numerous smaller islands. Between the Norfolk Ridge in the northeast and the Lord Howe Rise to the west of it extends the New Caledonia Trough , a depression that extends south to the Challenger Plateau. Another depression, the Bounty Trough , separates the Chatham Rise from the Campbell Plateau in the east.

geology

Zealandia's subsurface consists of continental crust , which has a thickness of 10 to 30 km and in Southland , in the south of the South Island of New Zealand, is thicker than 40 km. Thus, the earth's crust of Zealandias turns out to be overall thinner than that of other continents, whose crust is on average between 30 and 46 km thick, but also thicker than ordinary oceanic earth crusts, which have an average thickness of 7 km. The thinnest crust of Zealandias is 2200 km long, 200 to 300 km wide and 1500 to 3500 m deep New Caledonia Trough.

The peculiarities of Zealandia are possibly due to different tectonic processes of the past 400 million years. 125 to 400 million years ago, when today's part of Zealandia was still part of Gondwana , the Pacific plate moved towards the eastern border of Gondwana. Layers of sediment were raised and raised to form mountains. About 125 million years ago the process was reversed and the plates diverged for about 100 million years. Zealandia split off from the Australian continent , creating the Tasman Sea , and stretching the earth's crust. While the seabed of the Tasman Sea later rose, the eastern part, Zealandia, subsided and sank mostly in the ocean. Around 23 million years ago the situation changed again and the Pacific plate again migrated westwards against the Australian plate , a process that is still ongoing. Under renewed pressure, New Zealand and the folds of its mountain ranges, especially the New Zealand Alps, emerged .

However, while the Pacific Plate pushes itself under the Australian Plate on the North Island of New Zealand and north of it, the two plates on the South Island and south of it work sideways against each other, so that the part east of the Alps moves south and the western part slightly north. It is probably due to this process that an offset has arisen between the New Caledonia Trough north of the Challenger Plateau and the Bounty Trough east of New Zealand and both, which originally represented a contiguous depression in the continent, are now separated.

Volcanism occurred in Zealandia before, during and after Antarctica and Australia separated from Gondwana. Even if Zealandia is up to 6000 km away from Antarctica, the underlying magma has the same composition as that of the volcanic processes in Australia and Antarctica. Volcanic formations are widespread, but apart from the large shield volcanoes that formed the Banks Peninsula and Otago Peninsula , only small amounts of volcanic products were extracted. The main volcanic phases were in the Upper Cretaceous and the Cenozoic . The cause of the volcanism is unclear; it may be traced back to a mantle plume over which Zealandia passed and triggered hotspot volcanism. This is how the chain of submarine volcanoes of the Lord Howe Seamount Chain could have originated.

A petrified tree trunk on the banks of Curio Bay

In Curio Bay , petrified tree trunks and rootstocks preserved in a living position form a petrified forest . The trees were related to modern kauri trees and araucarias and grew in the Jura before 180 Ma, before the separation of Zealandias from Gondwana. The forest was covered by volcanic mud flows . During the diagenesis of the mud, the plant material was replaced by silica and thus petrified. Today it is back on the surface of the earth, exposed by the erosion caused by the surf .

During the last glacial periods , a larger part of Zealandias must have reached above the sea surface than is the case today. This is indicated by the discovery of a mammalian jaw in the Otago area .

Resources and raw material deposits

The seabed of Zealandias is believed to be rich in raw materials. For years, the largely unexplored “continent” has been attracting increasing attention from the point of view of raw materials. In addition to the known deposits of oil and gas, sulphide and iron manganese nodules are also suspected.

Oil and gas deposits

Oil reserves have been known in New Zealand since 1865. In that year, Taranaki began to produce oil. 1959 followed the development of the Maui Gas Field off the Taranaki coast, which from 1979 made New Zealand more independent in the gas supply. In 1993, the McKee oil field was developed around 20 km off the coast of New Plymouth . Oil and gas has been suspected in 17 other submarine basins around New Zealand since the 1970s, and most of them have been actively drilled and searched for high-yielding fields.

Iron sand

Ferrous sands on the west coast of the Waikato and Taranaki regions of the North Island have been known to exist for over 150 years . Iron has been productively extracted and used for steel production since the 1960s, and in some cases it has also been exported.

Scientific discussion about viewing it as a continent

There are four basic criteria for considering part of the world as a continent:

  1. The continental crust must stand out sufficiently high from the oceanic crust.
  2. There must be a variety of rock types. These must consist of the three basic types of igneous , sedimentary and metamorphic rock . (Igneous rock is formed through volcanism , sedimentary rock through the accumulation and diagenesis of eroded sediments, and metamorphic rock through the transformation of sedimentary rock under pressure and heat in the earth's crust .)
  3. The continental crust must be thicker than the oceanic crust and the seismic velocity must be lower.
  4. The area in question must be large enough to be recognized as a continent rather than a microcontinent . However, a certain value of the required size has so far not been adequately discussed or specified in science.

Scientists put together the following arguments, according to which Zealandia should be considered a continent:

  1. With a combined size of 4.9 million km², Zealandia would be sufficiently large.
  2. Zealandia is separate enough from the Australian continent that it is not considered a fragment or a microcontinent. At its narrowest point, Zealandia is separated from Australia by a 25 km wide and 3,600 meter deep ditch.
  3. Zealandia stands out from the sea floor of the oceanic crust at an average height of 1100 m.
  4. Numerous geological surveys of the Zealandia islands and the seabed in the past 20 years have provided sufficient evidence that the minimum geological requirements typical of a continent are present. Granite , greywacke , slate and rocks containing silicon from the Paleozoic and Mesozoic Era were found everywhere .
  5. The crust is thinner than that of the other continents, but with a thickness between 10 and 30 km consistently more massive than ordinary oceanic earth crusts, which are usually 7 km thick.
  6. Furthermore, it is irrevocable that Zealandia once belonged to the supercontinent Gondwana and later split off from the continent of Australia .

literature

Web links

Individual evidence

  1. a b c d e f g Coordinates and longitudes of Zealandia were determined by Google Earth.
  2. a b Mortimer et al. 10 co-authors: Zealandia: Earth's Hidden Continent . In: GSA Today . 2017, p. 1 .
  3. ^ Keith Lewis, Scott D. Nodder, Lionel Carter: Sea floor geology - Zealandia: the New Zealand continent. In: Te Ara - the Encyclopedia of New Zealand. Ministry for Culture & Heritage, June 22, 2006, accessed February 25, 2017 .
  4. a b c Mortimer et al. 10 co-authors: Zealandia: Earth's Hidden Continent . In: GSA Today . 2017, p. 3 .
  5. Ellen Hunt: Zealandia - pieces finally falling together for continent we didn't know we had. In: The Guardian. February 17, 2017, accessed February 27, 2017 .
  6. Mortimer et al. 10 co-authors: Zealandia: Earth's Hidden Continent . In: GSA Today . 2017, p. 1-9 .
  7. Experience knowledge anew - oceans . BLV Buchverlag, Munich 2005, ISBN 3-405-16817-1 , The Pacific Ocean, p. 32-33 .
  8. Mortimer et al. 10 co-authors: Zealandia: Earth's Hidden Continent . In: GSA Today . 2017, p. 5 .
  9. ^ The History of Zealandia. GNS Science, accessed February 25, 2017 .
  10. ^ Curio Bay / Porpoise Bay. Department of Conservation , accessed January 21, 2016 .
  11. ^ Campbell, Hutching: In Search of Ancient New Zealand . 2007, p. 183-184 .
  12. Earth's newest continent 'Zealandia' was found thanks to a giant underwater land grab. In: Business Insider Australia. Allure Media, February 24, 2017, accessed February 28, 2017 .
  13. ^ New survey published on NZ mineral deposits. In: Crown Minerals. Ministry of Economic Development, May 30, 2007, archived from the original on October 16, 2008 ; accessed on February 28, 2017 (English, original website no longer available).
  14. ^ History of petroleum. In: Crown Minerals. Ministry of Economic Development, January 19, 2017, accessed February 28, 2017 .
  15. ^ History of minerals and coal. In: Crown Minerals. Ministry of Economic Development, January 19, 2017, accessed February 28, 2017 .
  16. a b Karl Urban: Is New Zealand a continent of its own? In: Neue Zürcher Zeitung . February 22, 2017, accessed January 18, 2019 .
  17. Mortimer et al. 10 co-authors: Zealandia: Earth's Hidden Continent . In: GSA Today . 2017, p. 2-3 .
  18. Mortimer et al. 10 co-authors: Zealandia: Earth's Hidden Continent . In: GSA Today . 2017, p. 3-5 .