94% of it is underwater: Meet Earth's "eighth continent"
A study receiving renewed attention this week brings Zealandia back to the headlines — a vast area almost entirely hidden beneath the South Pacific Ocean that researchers have proposed defining as Earth's eighth continent. Zealandia spans about 4.9 million square kilometers, but about 94% of it is below sea level.
A study receiving renewed attention this week brings Zealandia back to the headlines — a vast area almost entirely hidden beneath the South Pacific Ocean that researchers have proposed defining as Earth's eighth continent. Zealandia spans about 4.9 million square kilometers, but about 94% of it is below sea level. New Zealand and New Caledonia are among its most prominent parts that are above water.
It is an area of about 4.9 million square kilometers in the southwest Pacific Ocean. However, unlike the continents we are familiar with, almost all of it is underwater. Only a small part of it protrudes above sea level, and that is where, among others, New Zealand and New Caledonia are located. Simply put, what we see as islands above sea level are actually the high parts of a much larger landmass that continues underwater.
Here it is important to understand what makes a continent a continent: the coastline we see on a map is not necessarily its true boundary from a geological perspective. Even the continents we know continue below sea level. Therefore, researchers examine the type of soil and rocks underwater, the thickness of the Earth's crust, and the structure of the region.
In the case of Zealandia, researchers found several characteristics that fit a continent: it is relatively high compared to the surrounding ocean floor, composed of different types of rocks, has a continental crust thicker than normal oceanic crust, and spans a large and relatively distinct area. That is, from a geological perspective, the claim is that it is not simply a few islands scattered in the ocean, but the visible parts of one large landmass.
Despite the intriguing headlines about a "lost continent," researchers did not suddenly discover a vast area that was not known before. The name Zealandia was proposed as early as 1995, and in 2017 a group of researchers published a scientific paper in which they presented evidence that the region should be treated as a continent in its own right. The study consolidated years of geological and geophysical information and presented Zealandia as a single landmass, rather than a collection of islands and submerged land parts. Therefore, the innovation is not the existence of the area itself, but the way scientists understand and classify it.
The great difficulty in studying Zealandia is clear: if almost the entire continent is under the ocean, it is impossible to simply go out and map it as one maps a normal land area. Researchers had to rely on a combination of rock samples from the seabed, measurements of gravity and the magnetic field, seismic data, and mapping of the ocean floor.
In 2023, the New Zealand research institute GNS Science announced that the geological mapping of Zealandia had been completed down to its underwater edges. According to the institute, this made Zealandia the first continent whose geology has been mapped down to its boundaries underwater.
There is no single global body that officially decides how many continents exist, and the number we know from school also depends on the counting method. In some places, for example, Europe and Asia are counted as two continents, and in others they are treated as one continent — Eurasia. Zealandia is defined by researchers as a continent from a geological perspective. Therefore, when it is added to the seven known continents by the common counting method, it can be called the "eighth continent."
