Zealandia

Zealandia (pronounced ), also known as (Māori) or Tasmantis (from the Tasman Sea), is an almost entirely submerged mass of continental crust in Oceania that subsided after breaking away from Gondwana 83–79 million years ago. It has been described variously as a submerged continent, continental fragment, and microcontinent. The name and concept for Zealandia was proposed by Bruce Luyendyk in 1995, and satellite imagery shows it to be almost the size of Australia. A 2021 study suggests Zealandia is over one billion years old, about twice as old as geologists previously thought it was.

By about 23 million years ago, the landmass may have been completely submerged. Today, most of the landmass (94%) remains submerged beneath the Pacific Ocean. New Zealand is the largest portion of Zealandia above sea level, followed by New Caledonia.

Mapping of Zealandia concluded in 2023. With a total area of approximately , Zealandia is substantially larger than any other features termed microcontinents and continental fragments. If classified as a microcontinent, Zealandia would be the world's largest microcontinent. Its area is six times the area of the next-largest microcontinent, Madagascar, and more than half the exposed land area of the Australian continent. Zealandia is more than twice the size of the largest intraoceanic large igneous province (LIP) in the world, the Ontong Java Plateau (approximately ), and the world's largest island, Greenland (). Zealandia is also substantially larger than the Arabian Peninsula (), the world's largest peninsula, and the Indian subcontinent (). Due to these and other geological considerations, such as crustal thickness and density, some geologists from New Zealand, New Caledonia, and Australia have concluded that Zealandia fulfills all the requirements to be considered a continent rather than a microcontinent or continental fragment. Geologist Nick Mortimer commented that if it were not for the ocean level, it would have been recognised as such long ago.

Zealandia supports substantial inshore fisheries and contains gas fields, of which the largest known is the New Zealand Maui gas field, near Taranaki. Permits for oil exploration in the Great South Basin were issued in 2007. Offshore mineral resources include ironsands, volcanic massive sulfides and ferromanganese nodule deposits.

Etymology GNS Science recognises two names for the landmass. In English, the most common name is Zealandia, a latinate name for New Zealand, itself referring to the Dutch Zeeland province; the name was coined in the mid-1990s and became established through common use. In the Māori language, the landmass is named , meaning 'the hills, valleys, and plains of Māui'.

Geology

Biogeography New Caledonia is at the northern end of the ancient continent, while New Zealand rises at the plate boundary that bisects it. These land masses constitute two outposts of the Antarctic flora, featuring 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 approximately 180 million years ago during the Jurassic period, before it split from Gondwana. The trees growing in these forests were buried by volcanic mud flows and gradually replaced by silica to produce the fossils now exposed by the sea.

As sea levels drop during glacial periods, more of Zealandia becomes a terrestrial environment rather than a marine environment. Originally, it was thought that Zealandia had no native land mammal fauna, but the discovery in 2006 of a fossil mammal jaw from the Miocene in the Otago region demonstrates otherwise.

Political divisions

The total land area (including inland water bodies) of Zealandia is . Of this, New Zealand comprises the overwhelming majority, at , or 93.49%) that includes the mainland (North Island and South Island), the nearby islands, and most outlying islands, including the Chatham Islands, the New Zealand Subantarctic Islands, the Solander Islands, and the Three Kings Islands (but not the Kermadec Islands or Macquarie Island (Australia), which are parts of the rift).

New Caledonia and the islands surrounding it comprise some or 6.48%) and the remainder is made up of various territories of Australia including the Lord Howe Island Group (New South Wales) at or 0.02%), Norfolk Island at or 0.01%), as well as the Cato, Elizabeth, and Middleton reefs (the Coral Sea Islands Territory) with .

Population the total human population of Zealandia is approximately 5.4 million people. The largest city is Auckland with about 1.7 million people; roughly one-third of the total population of the submerged continent.

– 5,112,300 (France) – 268,767 (Australia) – 1,748 Lord Howe Island Group (Australia) – 382 Cato Reef (Australia) – 0 Elizabeth Reef (Australia) – 0 Middleton Reef (Australia) – 0

Zealandia

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