In 2017, geologists argued that Earth has an eighth continent; Zealandia covers 4.9 million square kilometres, with 94% lying beneath the Pacific

Most continents are easy to recognise. Their mountains, plains and coastlines rise above the oceans and appear clearly on a map. Zealandia is different. Much of this enormous geological region cannot be seen from the surface because it lies beneath the southwest Pacific Ocean. Only its highest portions, including New Zealand and New Caledonia, rise above sea level. The idea that this submerged region should be treated as a continent challenged the familiar picture of Earth's surface. Still, it was based on a geological argument rather than simply on what can be seen from land.

According to a 2017 study published in GSA Today, Zealandia covers about 4.9 million square kilometres, is 94% submerged, and consists predominantly of continental crust. The researchers argued that its large area, isolation from Australia, elevated seafloor and distinctive continental rocks and crustal structure supported treating Zealandia as a continent rather than as a collection of islands or fragments. The highest point of Zealandia is Aoraki/Mount Cook in New Zealand, at 3,724 metres above sea level.

A continent hidden beneath the ocean


Scientists had recognised for decades that the crust beneath New Zealand and neighbouring parts of the Pacific was unusual. In 1995, geophysicist Bruce Luyendyk proposed the name Zealandia for a broad geological region that included New Zealand, the Chatham Rise, the Campbell Plateau and the Lord Howe Rise. The question was whether this region could be considered a continent. Although traditional maps tend to define continents by visible landmasses, geologists also classify them based on the characteristics of their underlying crust. Continental crust generally differs from oceanic crust in its composition, thickness and structure, making these geological features central to the argument over Zealandia’s status.

The researchers found that Zealandia met several of these geological characteristics. Its crust is substantially elevated relative to the surrounding oceanic crust and contains a range of silica-rich rocks associated with continental environments. Its crust is also relatively thick and has seismic characteristics that distinguish it from the thinner oceanic crust around it. Another important feature is its coherence. Rather than being a random collection of submerged fragments, Zealandia forms a broad, continuous region of continental crust. Its boundaries can be traced following changes between the continental crust of Zealandia and the surrounding oceanic crust.

How did Zealandia end up underwater?

Zealandia's unusual position is closely linked to the breakup of Gondwana, the ancient supercontinent that once brought together much of today's Southern Hemisphere landmasses. The geological evidence indicates that Zealandia was once connected to other parts of Gondwana. During the Late Cretaceous, the continental crust in this region underwent extensive stretching and thinning as tectonic forces pulled the landmass apart. As the crust became thinner, much of Zealandia gradually subsided. This helps explain why Zealandia is unlike any other continent we know of. It was not simply a case of the land going underwater. Rather, its continental crust subsided underwater without actually moving away from the same geological area.

This also explains why the seafloor around New Zealand is not simply ordinary ocean floor. Zealandia is made of continental crust that extends well below sea level, while parts of the same crust have been uplifted to form New Zealand's mountains. A 2025 review in the New Zealand Journal of Geology and Geophysics notes that Zealandia's continent-ocean boundaries commonly lie at depths of about 2,500 to 4,000 metres below sea level, where the continental margin gives way to the surrounding oceanic crust and abyssal plains. These depths describe the largely submerged continental platform, not the elevation of its highest terrain. In New Zealand, tectonic forces have uplifted parts of this continental crust to form high mountains, including Aoraki/Mount Cook, which rises to 3,724 metres above sea level. The contrast between deep submerged margins and high mountain ranges reflects the varied topography of a large, stretched continental block rather than a break in its geological continuity. This submerged yet continuous continental crust was central to the 2017 proposal that Zealandia should be recognised as a continent.

Why the 2017 proposal mattered

The significance of Zealandia was not that scientists had added another coloured shape to a classroom map. The proposal offered a way to study how continents can stretch, break apart and eventually become largely submerged while retaining their continental identity. The researchers argued that recognising Zealandia as a continent provided a clearer framework for investigating continental rifting and the breakup of supercontinents. It also brought together geological evidence from rocks, bathymetry and crustal structure that had previously been considered across separate fragments.

There is an important distinction, however. As GSA Today notes, the proposal for Zealandia was a scientific argument for recognising it as a continent, not a formal decision by an international authority to change a universally agreed list of continents. Because there is no single globally binding definition of a continent, Zealandia’s status depends on the geological criteria being applied.

Zealandia therefore offers a rare example of a continent whose continental nature does not depend on how much of it rises above sea level. Much of its landmass lies beneath the Pacific Ocean, yet its crust retains the geological characteristics of a continent. Shaped by the stretching and breakup of Gondwana, Zealandia shows that a continent can be defined by what lies beneath the ocean as much as by what is visible above it.