Millions of People Inhabit This 'Hidden Continent' That's 94% Underwater

Sunlight illuminates the ocean around New Zealand's North and South islands in this photo taken by an astronaut aboard the International Space Station in 2014. NASA

Earth is usually said to have six or seven continents, depending whether you separate Eurasia into Europe and Asia. While everyone may not agree on where to draw the lines, however, at least the basic layout of landmasses is set in stone, so to speak. Continents do merge and break apart over time, but the process is so slow they've barely seemed to budge throughout human history.

Nonetheless, one plucky little continent managed to hide under our noses until fairly recently. Many scientists now believe Earth has a long-overlooked seventh (or eighth) continent, identified as "Zealandia" in a 1995 study, covering about 1.9 million square miles (4.9 million square kilometers). That's more than half the size of Australia, or roughly big enough to hold seven Texases.

How did we miss something so big? To our credit, it was hiding in something even bigger: the Pacific Ocean.

About 94% of Zealandia is currently covered by seawater, according to a 2017 study, with only a few of its highest elevations poking above the ocean surface. This may have delayed our discovery of the overall landmass, but people have actually inhabited some of Zealandia's highlands for centuries without quite realizing their continental context.

topographical map of Zealandia
This topographical map shows the submerged continent of Zealandia, outlined in pink, surrounding the exposed highlands of New Zealand. NOAA/Wikimedia Commons

There's an elevated region in the center of Zealandia, for example, that includes most of its dry land — along with nearly 5 million people. We know this as New Zealand, a famously beautiful island nation from which Zealandia draws its name. Nearly 1,200 miles (2,000 km) to the north, another ridge on the continent's northern edge rises high enough to form the archipelago of New Caledonia. The rest of Zealandia's dry land consists of small Australian territories, including Norfolk and Lord Howe islands.

Scientists had some idea about the system of ridges and basins around New Zealand as far back as 1919, but the full picture developed slowly, gaining little public attention until recently. As mapping technology improved, it began to show this region of crust wasn't fragmented into smaller pieces as once thought, instead forming a more continuous whole. In 2017, two decades after geophysicist Bruce Luyendyk proposed the name Zealandia, a team of geologists published a study concluding that Zealandia meets all the criteria to qualify as a continent.

(It's worth noting there is no universal scientific definition of what makes a continent a continent, but the study's authors cited several qualifications they say are "generally agreed" upon.)

"Continents are Earth's largest surficial solid objects, and it seems unlikely that a new one could ever be proposed," the study's authors wrote, yet they went on to propose just that. Zealandia covers a large, well-defined area that's isolated from the Australian continent, they note, and has thicker planetary crust than what's typically under oceans. They argue these and other traits — like its variety of silica-rich igneous, metamorphic and sedimentary rocks — support Zealandia's promotion to continent.

A new wave of scientific interest is now washing over Zealandia, as researchers study the crust in hopes of shedding light on the region's history, including its submergence after breaking up with the ancient supercontinent Gondwana. And while the name Zealandia seems to have stuck, there is also an effort in New Zealand to give the continent an additional name in honor of its indigenous Māori people: Te Riu-a-Māui, meaning "the hills, valleys and plains of Māui."

"Māui is an ancestor of all Polynesians. He sailed and explored the great ocean and caught the fish which he and his crew pulled up. The fish became many of the islands we know today," explains GNS Science, a New Zealand Crown Research Institute. Riu can mean the hull of a canoe, the core of a body or "the whole that holds the parts together," GNS adds. "Te Riu-a-Māui brings together geological science and the traditional oral narratives of Māui's exploits across the Pacific Ocean."

Topographical map of Zealandia: U.S. National Oceanic and Atmospheric Administration/Wikimedia Commons