Zealandia

Zealandia (pronounced /ziːˈlændiə/), also known as Te Riu-a-Māui (Māori)^[2] or Tasmantis (from Tasman Sea),^[3][4] is an almost entirely submerged mass of continental crust in Oceania that subsided after breaking away from Gondwana 83–79 million years ago.^[5] It has been described variously as a submerged continent, continental fragment, and microcontinent.^[6] The name and concept for Zealandia was proposed by Bruce Luyendyk in 1995,^[7] and satellite imagery shows it to be almost the size of Australia.^[8] A 2021 study suggests Zealandia is over a billion years old, about twice as old as geologists previously thought.^[9][10]

By approximately 23 million years ago, the landmass may have been completely submerged.^[11][12] Today, most of the landmass (94%) remains submerged beneath the Pacific Ocean.^[13] New Zealand is the largest part of Zealandia that is above sea level, followed by New Caledonia.

Mapping of Zealandia concluded in 2023.^[14] With a total area of approximately 4,900,000 km² (1,900,000 sq mi),^[6] Zealandia is substantially larger than any 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 Madagascar, the next-largest microcontinent in the world,^[6] and more than half the 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 1,900,000 km² or 730,000 sq mi), and the world's largest island, Greenland (2,166,086 km² or 836,330 sq mi). Zealandia is also substantially larger than the Arabian Peninsula (3,237,500 km² or 1,250,000 sq mi), the world's largest peninsula, and the Indian subcontinent (4,300,000 km² or 1,700,000 sq mi). Due to these and other geological considerations, such as crustal thickness and density,^[15][16] 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.^[6] Geologist Nick Mortimer [de] commented that if it were not for the ocean level, it would have been recognised as such long ago.^[17]

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.^[18] Offshore mineral resources include ironsands, volcanic massive sulfides and ferromanganese nodule deposits.^[19]