Zealandia (continent) Totally Explained

Everything about Zealandia Continent totally explained

Zealandia, also known as Tasmantis or the New Zealand continent, is a nearly submerged continent or microcontinent that sank after breaking away from Australia 60-85 million years ago and from Antarctica between 130 and 85 million years ago. It may have been completely submerged about 23 million years ago, and most of it (93%) remains submerged beneath 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, The seemingly separate Gilbert Seamount (northwest of Fiordland) is also part of the New Zealand continent, 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, near Taranaki. Permits for oil exploration in the Great South Basin were issued in 2007. Offshore mineral resources include iron sands, volcanic massive sulfides and ferromanganese nodule deposits.

Geology

Unlike most continents, Zealandia is largely made up of two nearly parallel ridges, separated by a failed rift. The ridges rise above the sea floor to depths of 1,000-1,500 meters, with infrequent rocky islands rising above sea level. The ridges are continental rock, but are lower in elevation than normal continents because their crust is thinner than usual (only about 20 kilometers thick), and consequently they don't float as high above 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. Movement along this plate boundary has also offset the New Caledonia Basin from its previous continuation through the Bounty Trough.
   Compression across the boundary has uplifted the Southern Alps, although due to rapid erosion their height reflects only a small fraction of the uplift. 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 with respect to the underlying mantle from the time when it rifted from Antarctica, recurring intracontinental volcanism exhibits magma composition similar to that of 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 that developed 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 lies at the northern end of the ancient continent, while New Zealand rises at the plate boundary that bisects it. These land masses are two outposts of the Antarctic Flora, including Araucarias and Podocarps. At Curio Bay, logs of a fossilized forest closely related to modern Kauri and Norfolk Pine can be seen that grew on Zealandia about 180 million years ago during the Jurassic period, before it split from Gondwana. These were buried by volcanic mud flows and gradually replaced by silica to produce the fossils now exposed by the sea.
During glacial periods more of Zealandia becomes a terrestrial rather than a marine environment. Zealandia has no native land mammal fauna.

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