The map showing how big Zealandia was, the continent submerged in the Pacific Ocean that took 375 years to find

Aristotle, Eratosthenes and later the cartographer Ptolemy called it Terra Australis Ignota.

In search of this imaginary continent, which in classical Greece was thought to exist on the other side of the world due to geometric symmetry, the Dutch explorer Abel Tasman came across a new land in 1642: the islands we now know as New Zealand. Zealand. . But that seemed too small to be what I was looking for.

It took 375 years to confirm that the continent called Zeelandia actually existed, although it was largely invisible to the naked eye: It is 94% underwater.

Now a new study has managed to complete the definitive map of Zealandia, or, as it is known in Māori, Te Riu-a-Māui.

In a study published in “Tectonics,” scientists from GNS Science in New Zealand have created a new detailed map of Zealand’s borders thanks to rock samples dredged from the ocean floor.

The continent stretches out 5 million square kilometersand only now has its entire surface been determined.

Its history is linked to that of Gondwana, the ancient southern supercontinent which, when divided hundreds of millions of years ago, created the continents we know today and which, depending on the country one studied, may number six or seven.

Zealandia separated about 80 million years ago, but unlike the neighboring continents of Antarctica and Oceania Most of its territory was under water.

Basalt, sandstone and pebble

The only land remaining on the surface is the islands of New Zealand, the French territory of New Caledonia, and the small Australian territories of Lord Howe Island and Ball’s Pyramid.

Because Zealandia was under the ocean, it was little and poorly studied, creating inconsistencies about its shape and boundaries. Until now, only the southern part of the continent had been mapped.

With new research led by geologist Nick Mortimer, the missing two-thirds are defined and existing maps have been refined so that “geological land and marine reconnaissance mapping of the entire 5 million km2 continent of Zeeland is now complete,” the study notes.

To do this, the team of geologists and seismologists studied the samples of rocks and sediments collected from the ocean floor, mainly through drilling, and also the specimens that appeared on the shores of the islands in the area.

They were analyzed and dated basalt, sandstone and sandstone pebbles. The researchers found that the sandstones were from the Upper Cretaceous (about 95 million years old) and contained granites and volcanic pebbles from the Lower Cretaceous (130 to 110 million years old). The basalts date from the Eocene (about 40 million years old).

These results, along with data from regional magnetic anomalies and information from other studies, have helped scientists map the underwater geology of North Zealand.

After that first European sighting in 1642 by Abel Tasman (who would later name the island Tasmania), other explorers and scientists searched the waters of Zealand in search of the lost continent. without realizing they were hovering above him.

The first real evidence of its existence was gathered by Scottish naturalist James Hector, who in 1895 studied the islands off the south coast of New Zealand and concluded that the country is “the remnant of a mountain range which formed the summit of a large continental area. area that extended south and east, and is now underwater.”

Then, in 1995, American geophysicist Bruce Luyendyk returned to described the region as a continent and suggested calling it Zealandia.

That changes?

The continental crust is usually about 40 km deep and considerably thicker than the oceanic crust, which is usually only about 10 km deep.

Zeeland has a few 20 km deep because the platform expanded enormously when it separated from Gondwana. Because it was so thin, it eventually sank, although not to the level of normal oceanic crust.

Scientists argue that Zealandia, both because of the height of its crust and the types of rocks it is composed of, is definitely a continent.

Apart from scientific interest, does it change anything if researchers define Zeeland as a new continent?

Well, yes.

According to United Nations Convention on the Law of the Seacountries can extend their legal territories beyond their Exclusive Economic Zone, which extends 370 km from their coast, to claim their “extended continental shelf”, with all the mineral and oil resources this includes.

By proving that it is part of a larger continent, New Zealand could increase its territory sixfold.

This has led to an increase in funding for marine exploration in recent years. (JO)