We have been taught since childhood that there are seven continents and four oceans on the earth, but if I tell you now,In fact, there are eight continents on the earth, but one of them is "hidden", and now scientists have not only found it, but also mapped it for the first time. What do you think?

Picture: The eighth continent synthesized by the artist

The story of the eighth continent on Earth begins much longer than we imagine.

As early as 1642, the Dutch voyage explorer Abel Tasman set out from Europe and headed south. He and his fleet had only one purpose, which was to find a southern hemisphere continent that could balance the northern hemisphere continents, and they named this potential southern hemisphere continent Australia in advance.

They searched for the South Island of New Zealand, but were blocked by the Maori who had already settled there, and did not land on the island because they did not think it was their legendary continent.

In fact, Europeans at that time already knew what is now Australia, but they did not think it was the legendary continent they were looking for. Of course, they later changed their minds, so Australia now has this name.

Although Abel did not find the continent in European legend, he believed for the first time that this continent was "hidden".It must be somewhere in the southern hemisphere, perhaps underwater.

The turning point of the story occurred in 2017. After 375 years of searching, scientists finally announced that the "hidden continent" in the southern hemisphere had been found. It covers an area of ​​more than 5 million square kilometers, twice the area of ​​the Indian subcontinent.

This continent was named Zealandia, or Zealandia. Its name comes from the Maori language, but the Maori people have never experienced its sinking (we will introduce its history later).

Only two parts of Zealandia are now exposed to the water. One part is New Zealand, which is the highest mountain range of the original Zealandia, and the other part is the New Caledonia Islands in the north. More than 94% of the other continental area is underwater.

Ever since Zealandia was identified, people have tried to map the continent, but since most of its area is 600-1500 meters underwater, this has not been easy.

Scientists have long produced this first map (below) by analyzing rock samples recovered from the ocean and geophysical mapping.

Pictured: Newly published map of Zealandia

Pictured: Satellite photo of Zealandia

However, you may have many questions, such as why this continent has not been discovered until now. Does it really take so long to find it with the current technology?

In fact, the reason why this new continent has not been discovered until now has nothing to do with technology.The main reason is that it has no value of discovery until now.

Because the United Nations Convention on the Law of the Sea came into effect in 1994, the legal territory of each country can extend to 200 nautical miles (370 kilometers) beyond its coastline, and coastal countries will own the "extended continental shelf" and all mineral resources and oil contained therein.

Enthusiasm for the search for new continents was also reignited from that time, the most active being New Zealand, which could expand its territory six times if they could prove it was part of a larger continent.

So, can this newly discovered continent be considered a continent?

As far as the current scientific definition is concerned, the newly discovered land is indeed closer to the definition of a continent, but it is estimated that few people will admit that it really belongs to the eighth continent. After all, the debate between the five continents and the seven continents has not stopped yet.

What makes a region a continent?

In fact, the definition of continent in geology is relatively vague, which is why there is so much controversy. It does not define whether a continent is covered by water. After all, coastal continental shelves (the gentle parts of continents that extend into the ocean) are also considered continents.

At present, judging whether an area is a continent or an ocean mainly depends on its crustal composition. The crust of a continent is mainly composed of igneous rocks, metamorphic rocks and sedimentary rocks. Compared with the surrounding seafloor, a continent should also have a high-relief area.

The oceanic crust is composed of basalt, which is thinner and denser than the continental crust, and its terrain is lower.

Figure: Continental Earth and ocean crust are not the same

Zealandia meets the definition of a continent. It is indeed composed of a continuous piece of continental crust, and it is indeed about 3,000 meters higher than the oceanic crust.

Most importantly, it is physically separate from Australia's continental crust, so it could theoretically be classified as a separate continent.

But how did this continent become what it is now, and what happened in its past?

While drawing the map, scientists also studied the past of this lost continent. Through analysis of rocks and crust, scientists speculated that Zealandia began to gradually sink about 40 million years ago, and there were no humans at that time.

Pictured: Artist’s synthesis of Atlantis

Why did Zealandia sink to the bottom of the sea?

In recent decades, scientists have learned a great deal about plate tectonics and continental drift, and it is now generally accepted that all of Earth's landmasses were once part of a single supercontinent called Pangea.

About 230 million years ago, Pangea began to split into Laurasia and Gondwana, one to the north and the other to the south.

About 180 million years ago, Gondwana also began to break apart to the south, becoming today's Australia, Antarctica, South America, Africa, the Indian subcontinent, and other scattered components.

Among them, the Himalayas were formed when the Indian subcontinent drifted northward and hit Asia.

It seems that Gondwana is inherently unstable. About 85 million years ago, Zealandia separated from Australia. After the separation, Zealandia also inherited the instability of Gondwana. After that, it continued to be stretched as if it was about to be "disintegrated".

The depth of continental crust is usually about 40 kilometers (oceanic crust is usually 10 kilometers), but Zealandia's is only 20 kilometers. This is the result of it being stretched and the reason why it sank, because the continent became thinner and the sea water submerged it!

This is the whole story of Zealandia,it was submerged but found again, just like in the legend.