Zealandia, a new continent that is almost entirely submerged, proposed by geologists

It’s not Atlantis, the legendary island that that is thought to have sunk. It’s Zealandia, a real continent located in the southwestern Pacific Ocean, whose landmass of 4.9 million square kilometers is 94% submerged. The 6% of Zealandia that sits above sea level includes the two islands of New Zealand—the inspiration for the continent’s name—and the archipelago of New Caledonia. The proposal to consider this large block of continental crust as a continent, like Africa, North America, South America, Antarctica, Australia and Eurasia, came from a team headed by Nick Mortimer of GNS Science, formerly known as the New Zealand Institute of Geological and Nuclear Sciences (GSA Today, February 9, 2017). According to the study’s authors, although most of Zealandia lies beneath the Pacific, it exhibits the principal geological and geophysical features that characterize areas of continental crust, as opposed to oceanic crust. Its composition is essentially granitic, “lighter” than that of oceanic crust, which is basaltic. It has higher elevations—the reason why most of the land mass of the other continents lies above sea level. Its thickness is greater, about 35 kilometers; oceanic crust averages up to 8 kilometers thick. The Earth is the only planet in the Solar System whose crust is divided into two types, continental and oceanic. Geologists attribute the uplift of granitic crust—in other words, of the continents—to the movement of tectonic plates. In addition to this geological definition of a continent, there are also geographical and geopolitical definitions.