Zealandia – The 8th Continent

Earth is known to have seven continents sprawled across the planet at present. A team of scientists, however, might disagree with this. The reason for this is that they have discovered a previously unknown landmass submerged around 3,500 feet under the south Pacific, not Atlantis but Zealandia.

Considered to be a lost “eighth continent” that got submerged underwater millions of years ago, the landmass is called Zealandia. Researchers from GNS Science in New Zealand have now mapped the shape and size of the continent with utmost detail.

For the mapping, the researchers analysed the bathymetry – the shape and depth of the ocean floor around Zealandia. Also, they studied its tectonic profile to accurately locate Zealandia across tectonic-plate boundaries.

Decades of evidence:

The new study synthesizes decades of evidence for a hidden continent lying beneath the ocean surrounding New Zealand. The first line of evidence comes simply from looking at the ocean floor around New Zealand: The continental shelves of Zealandia lie at a depth of about 3,280 feet (1,000 meters) below sea level, while the nearby oceanic crust is about 9,800 feet (3,000 m) below. Just like other continents, Zealandia has a huge range in altitude, from the sub-ocean depths to Aoraki/Mount Cook at 12,217 feet (3,724 m) above sea level.

The second line of evidence supporting Zealandia’s designation as a separate continent comes from extensive study of the rocks beneath the ocean. Over the past 20 years, geologists have set sail on ships to dredge rocks from the seafloor. Unlike the nearby oceanic crust, which is made up of basaltic rocks from the fairly recent geologic past, the crust surrounding New Zealand is composed of a variety of different rock types, including granite, limestone and sandstone, some of which are incredibly ancient. That is typical of continental crust, the researchers reported in the March/April issue of the journal GSA Today.

Finally, scientists have shown that there’s a narrow strip of oceanic crust separating the continent of Australia from the subterranean reaches of Zealandia, meaning the two are separate continents.

Zealandia continent lost underwater:

Zealandia’s total area has been mapped to be nearly 2 million square miles (5 million square kilometres). At this measure, Zealandia is about half the size of Australia, however, only 6% of the continent is above sea level.

The part above water forms the foundation of New Zealand’s north and south islands as well as the island of New Caledonia. The rest of Zealandia is underwater and thus had to be mapped for its ocean floor too, hence a bathymetric map.

A startling revelation of the bathymetric map is the continent’s steep mountains and ridges rising towards the surface of the water. In addition to mountains and ridges, the map shows coastlines, territorial limits, and major undersea features. 

How did the Zealandia continent sink?

The idea of a potential continent in this area has been around for some time, and the name “Zealandia” was first coined by geophysicist Bruce Luyendyk in 1995.

The dedicated study of this area, stretching about 5 million square kilometres (about 1.93 million square miles), has since determined it is not just a group of continental islands and fragments, but a continental crust large and separate enough to be officially declared a separate continent.

Zealandia used to be part of Gondwana, the supercontinent that once held many of the continents we know today, like Africa and South America.

About 85 million years ago, Zealandia split off from Gondwana. The drifting, shifting landmass, about half the size of Australia, was home to dinosaurs and lush rainforest.

What is Ring of Fire?

Millions of years later, the world’s tectonic plates of the Earth’s crust began reorganizing themselves, in a period of dramatic geological change that also created the Pacific “Ring of Fire,” a belt in the Pacific where the world’s most active volcanoes are located.

During this time, the Pacific Plate – the world’s largest tectonic plate is believed to have sunk below the continental crust of Zealandia. This process, called subduction, caused the root of the continent to break off and sink as well, according to the National Science Foundation.

Abut 94% of Zealandia is now submerged underwater but some parts of the continent are still above land, making up New Zealand and other small islands. The highest point of Zealandia is Aoraki Mount Cook at 3,724 meters (12,218 feet).

There is still much unknown about the continent and whether the discovery of Zealandia could change historical climate models. As more research emerges, the interactive website and maps will be updated to reflect what we know.

Image Courtesy: www.youtube.com

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