Zealandia is a mostly submerged continent in the southwestern Pacific Ocean, with about 95% of its nearly 5 million square kilometers sitting beneath the waves. Only New Zealand and New Caledonia poke above the surface. It’s roughly the size of the Indian subcontinent and covers about 6% of Earth’s total land surface, making it larger than Australia by area percentage.
Why Geologists Call It a Continent
For decades, the landmass beneath New Zealand was treated as a collection of continental fragments rather than a single, unified continent. That changed in 2017, when a team of geologists published a landmark paper in GSA Today (the journal of the Geological Society of America) titled “Zealandia: Earth’s Hidden Continent,” arguing it met all four criteria that define a continent.
Those criteria are: elevation higher than the surrounding oceanic crust, a wide variety of rock types including igneous, metamorphic, and sedimentary rocks, a crust that is thicker and structurally distinct from ocean floor, and well-defined boundaries around an area large enough to qualify as a continent rather than a fragment. Zealandia checks every box. Its crust is continental in composition, generally 10 to 30 kilometers thick compared to the 7 kilometers typical of oceanic crust. And its boundaries are clearly distinguishable from the thin oceanic crust that surrounds it.
The name itself dates back to 1995, when geophysicist Bruce Luyendyk at the University of California, Santa Barbara, proposed a model for how the ancient supercontinent Gondwana broke apart. He collectively named the submerged landmass that includes New Zealand “Zealandia.” In te reo Māori, the continent is known as Te Riu-a-Māui.
How Zealandia Ended Up Underwater
Zealandia was once part of Gondwana, the massive southern supercontinent that also included what is now Australia, Antarctica, South America, Africa, and India. Starting around 85 to 130 million years ago, tectonic forces began pulling Zealandia away from Gondwana and Antarctica. As it separated, the crust stretched and thinned, much like pulling taffy. That thinning caused the landmass to sink gradually beneath the ocean surface.
The process took tens of millions of years. By roughly 23 million years ago, Zealandia was almost entirely submerged. What remains above water, New Zealand’s North and South Islands, New Caledonia, and a handful of smaller islands, represents only about 5% of the total continent. The rest lies beneath relatively shallow seas, with large plateaus and ridges visible in seabed mapping.
Ancient Life Preserved in Rock
Before Zealandia sank, it hosted a rich diversity of land animals. Fossils embedded in the basement rocks that Zealandia carried with it during its separation from Gondwana capture evidence of ancient vertebrate life, including amphibians, crocodilians, birds, lizards, and mammals. These fossils date back to the late Mesozoic era, when dinosaurs still roamed other continents.
As the landmass became increasingly isolated and submerged, the animals that survived on its remaining above-water portions evolved in remarkable ways. Flying species that dispersed to the shrinking islands eventually produced descendants famous for being flightless or nearly so. The kākāpō, the world’s heaviest parrot, lost the ability to fly entirely. The lesser short-tailed bat became increasingly ground-dwelling. Moa, the giant flightless birds hunted to extinction by early Polynesian settlers, left behind trackways preserved in Central Otago rock, with some of the oldest known moa footprints discovered in riverbed formations.
Fossils from Zealandia also include remarkably well-preserved freshwater ecosystems from around 23 million years ago: ancient lake beds in Otago containing diatoms, insects, fish, and plant material that offer a window into what life looked like on the continent just before it nearly disappeared beneath the sea.
What Lies Beneath the Seafloor
Zealandia’s status as a continent has practical consequences beyond geology textbooks. Under the United Nations Convention on the Law of the Sea (UNCLOS), a coastal nation can claim sovereign rights over the seabed and its resources along the “natural prolongation” of its land territory. This can extend well beyond the standard 200 nautical miles from the coast, up to 350 nautical miles or 100 nautical miles past the 2,500-meter depth line, whichever is greater.
New Zealand has used detailed marine surveys to map the extent of its continental shelf and submitted a formal claim under UNCLOS. The UN commission recognized the quality of New Zealand’s science and its interpretation of the relevant legal provisions. The claim area is roughly equivalent in size to Western Australia. Within these boundaries, New Zealand holds sovereign rights over non-living resources like oil, gas, and minerals in the seabed, as well as sedentary living organisms such as sponges and molluscs. A separate treaty with Australia establishes the boundary between the two countries’ claims in the Tasman Sea, giving both nations legal certainty over offshore resources including fisheries and petroleum.
How Zealandia Compares to Other Continents
At 4.9 million square kilometers, Zealandia is the smallest continent if it receives full recognition, roughly two-thirds the size of Australia. But “smallest” is relative. It is still vastly larger than Madagascar or any other landmass typically classified as a continental fragment. Its total area accounts for about 6% of Earth’s land surface, compared to Australia’s 5%.
What makes Zealandia unique is how much of it is hidden. Every other continent has the majority of its area above sea level. Zealandia is the opposite: a continent defined more by what you can’t see than what you can. Recent mapping efforts have rendered the submerged portions in unprecedented detail, revealing the full shape of its plateaus, ridges, valleys, and plains beneath the Pacific. These maps make the continental boundaries unmistakable, even though most people will never set foot on more than a sliver of Zealandia’s surface.