- Zealandia, also called Te Riu-a-Māui in Māori, is a nearly submerged continental mass in the southwest Pacific Ocean. It covers about 4.9 million square kilometers, making it roughly two-thirds the size of Australia, yet about 94% of its area lies underwater, with only a few portions—such as New Zealand’s North and South Islands, New Caledonia, and smaller islands—rising above sea level. Because of its size, distinct geology, and crustal thickness, many geologists classify Zealandia as Earth’s eighth continent, though it remains largely hidden beneath the ocean.
- Geologically, Zealandia broke away from the supercontinent Gondwana around 80 million years ago. Unlike oceanic crust, Zealandia is made of continental crust, composed of granites, sedimentary rocks, and metamorphic formations. Its crust is much thicker than that of typical ocean basins but thinner than most continents, which explains why much of it sank below the surface after rifting from Gondwana. Zealandia is tectonically active, lying across the boundary between the Pacific Plate and the Indo-Australian Plate, which accounts for the volcanic activity, mountain building, and frequent earthquakes in New Zealand.
- Zealandia is important for understanding Earth’s geological history because it challenges traditional definitions of continents. Its existence was first hypothesized in the mid-20th century, but widespread scientific recognition came only in the 21st century, after improved seafloor mapping and geological surveys revealed its extent and composition. In 2017, a team of geologists formally proposed Zealandia as a distinct continent, arguing that it meets the four main criteria: elevated area, distinctive geology, a well-defined area, and a crust thicker than the surrounding oceanic floor.
- Beyond its geological significance, Zealandia has played a vital role in the evolution of unique ecosystems. Its isolated landmasses, particularly New Zealand, became refuges for plants and animals after separating from Gondwana. This isolation led to the development of highly distinctive biodiversity, including flightless birds like the kiwi and the extinct moa, as well as ancient reptiles like the tuatara. Zealandia’s submerged ridges and plateaus also influence ocean currents and marine habitats, making it an ecological as well as geological treasure.
