Topography of Zealandia, outlined in pink. The linear ridges running north-northeast (Colville to the west and Kermadec to the east, separated by the Havre Trough and Lau Basin) and southwest (the Resolution Ridge System) away from New Zealand are not considered part of Zealandia, nor are Australia (left), Vanuatu, or Fiji (top centre).[1]
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 the next-largest microcontinent, Madagascar,[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 commented that if it were not for the ocean level, it would have been recognised as such long ago.[17]
^Gurnis, M., Hall, C.E., and Lavier, L.L., 2004, Evolving force balance during incipient subduction: Geochemistry, Geophysics, Geosystems, v. 5, Q07001, https://doi.org/10.01029/02003GC000681
^ abcdCite error: The named reference mortimer was invoked but never defined (see the help page).
^"Searching for the lost continent of Zealandia". The Dominion Post. 29 September 2007. Retrieved 9 October 2007. 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.
^Campbell, Hamish; Gerard Hutching (2007). In Search of Ancient New Zealand. North Shore, New Zealand: Penguin Books. pp. 166–167. ISBN978-0-14-302088-2.
^Wood, Ray; Stagpoole, Vaughan; Wright, Ian; Davy, Bryan; Barnes, Phil (2003). New Zealand's Continental Shelf and UNCLOS Article 76(PDF). Institute of Geological and Nuclear Sciences Limited. Institute of Geological and Nuclear Sciences series 56. Wellington, New Zealand: National Institute of Water and Atmospheric Research. p. 16. NIWA technical report 123. Archived from the original(PDF) on 21 February 2007. Retrieved 22 February 2007. 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.
^Sumner, Thomas (13 March 2017). "Is Zealandia a continent?". Science News for Students. Society for Science and the Public. Retrieved 22 December 2021.