2021-02-12

Tracing the Lost Continent of 375 Years: There are still many mysteries yet to be solved

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He believes that there is a vast continent in the southern hemisphere and is determined to find it.

For Europeans at the time, this part of the earth is still very mysterious, but they have an unshakable belief that there must be a large area of ​​land in the southern hemisphere-named “Australis” in advance -In order to reach a balance with the northern hemisphere continents. This obsession with the imaginary continent can be traced back to the ancient Roman era, but until this time no one tried to verify it.

So, on August 14 of that year, Tasman set off from his company’s base in Jakarta, Indonesia with two small boats, heading west, then south, and then east, and finally arrived in New Zealand. South island. His first contact with the local Maori was not smooth: the next day, a few people rushed out in a canoe and crashed into a small boat that was transmitting messages between Dutch ships. Four Europeans died. Later, the Europeans fired another shot at about 11 canoes. As for whether they hit the target, no one knows.

Tasman just ended his mission. He named this terrible place Moordenaers Bay (Moordenaers Bay, meaning “murderer” Bay)-without any irony. A few weeks later, he did not even set foot on this new land before taking the boat home. Although Tasman believes that he has indeed discovered the unknown southern continent, it is clear that this is not the commercial utopia he envisioned. He never returned here.

At that time, people already knew Australia. The English “Australia” is derived from the Latin “australis”, which means “south”. But Europeans think this is not the continent they are looking for in the legend. Later, when they changed their minds, the continent was renamed “Terra Australis”, or “Southern Continent”.

What Tasman didn’t expect was that he was right from start to finish-there was indeed a lost continent. In 2017, a group of geologists announced the discovery of the mainland of Zealand (Zealandia), also known as Zealandia, or “Te Riu-a-Māui” in Maori. The continent has a vast area of ​​4.9 million square kilometers, about six times that of Madagascar.

Although the encyclopedias, maps, and search engines of various countries have always insisted that there are only seven continents in the world, this research team confidently told the world that this conclusion is wrong. There are eight continents in the world, and this newly added continent is the smallest, thinnest and youngest among them. The problem is that 94% of this continent is underwater, and only a few islands (such as New Zealand) are exposed on the surface. In other words, it has always been hidden under our noses.

Andy Tullok, a geologist at the New Zealand Institute of Geographical Sciences, said: “This example shows that some obvious things will take some time to be discovered.” Tullok discovered the mainland of Zealand. One of the research team members.

However, this is only the beginning. Four years later, this continent is still as mysterious as ever, and its secrets are carefully preserved under the water at a depth of 2,000 meters. How is it formed? What kind of creatures used to live there? How long has it been underwater?

In fact, the study of the Sealand mainland has always been a difficult challenge. In 1642, Tasman discovered New Zealand. More than a century later, the British Royal Navy officer, explorer and cartographer James Cook was sent to the southern hemisphere for scientific voyages. The official instructions to him were to observe the transit of Venus and calculate the distance between the earth and the sun.

But Cook also carried a letter with him, and he was asked to open the envelope after completing the first task. The letter contained a top secret mission: exploring the southern continent. It can be said that before arriving in New Zealand, Cook sailed directly across this continent.

Tracing the Lost Continent of 375 Years: There are still many mysteries yet to be solved

Satellite data is available Used to show the continent of Sealand, it looks like a light blue inverted triangle located east of Australia

The first real clue about the existence of the continent of Sealand comes from the Scottish naturalist James Heck Sir Thor. In 1895, he took part in a voyage to a series of islands on the south coast of New Zealand. After studying the geology of these islands, he concluded that New Zealand is “the remnant of a mountain range, and this mountain range is the peak of a continental area that extends south and east and is now submerged…” /p>

Nevertheless, the understanding of the possible existence of Sealand has been very vague, and there was no progress until the 1960s. Nick Mortimer, a geologist at the New Zealand Institute of Geographical Sciences, who led the 2017 study, said: “The progress in this field is quite slow.”

In the 1960s, geologists finally A consensus was reached on the definition of “mainland”. Broadly speaking, a continent is a geological area with high altitude, a wide variety of rocks, and a thick crust. Of course, the area of ​​the mainland must also be large. “It can’t be just a small piece,” Mortimer said. After the definition is clear, geologists will have a research direction-if they can collect enough evidence, they can prove that the eighth continent is real.

However, this research is still stagnant-the discovery of a new continent needs to solve many difficult problems, and the cost is high. Mortimer also pointed out that the researchers have no sense of urgency. In 1995, American geophysicist Bruce Luendick once again referred to this area of ​​the southern hemisphere as a continent and proposed to name it as the continent of Sealand. Tulloch said that it was from that time that exploration of the continent began to increase exponentially.

About the same time, the “United Nations Convention on the Law of the Sea” came into effect, and finally provided some serious motivations. The convention states that countries can extend their legal territories beyond their exclusive economic zone [200 nautical miles (370 kilometers) from the coastline] in order to claim their “extended continental shelf”-and all the minerals and oil contained in the area- Advocate.

So, if New Zealand can prove that it is part of a larger continent, it can expand its territory six times. Suddenly, funding for related research became sufficient, and evidence gradually accumulated. With a large number of rock specimens collected by geologists, research on the Sealand continent has become more and more perfect.

Researchers are also supported by satellite data, which can be used to track the tiny changes in the earth’s gravity between different parts of the crust to draw a map of the sea floor. With this technology, the Sealand continent has become clearly visible, which is a strangely shaped continent almost the same size as Australia.

When researchers finally revealed the existence of this continent to the world, it became one of the world’s most extensive maritime territories. “It’s pretty cool,” Mortimer said. “Think about it. There are different countries on every continent on Earth, (but) there are only three territories on the Sealand.”

Except New Zealand, this continent also includes New Caledonia, Lord Howe Island and the Pyramid of Burr. New Caledonia is one of France’s overseas possessions and is famous for its magnificent lagoons; Lord Howe Island and Burr’s Pyramid are both Australian islands, the latter being described by an 18th-century explorer as ” Smaller than a ship”.

The Sealand continent was originally part of the ancient Gondwana supercontinent, which was formed about 550 million years ago and is basically the sum of all the land in the southern hemisphere. Sealand occupies a corner on the east side of Gondwana and borders several other regions, including half of West Antarctica and the entire East Australia.

Then about 105 million years ago, “Due to a process that we did not fully understand, the Sealand continent began to separate from Gondwana,” Tulloch said.

The continental crust is usually about 40 kilometers deep, which is significantly thicker than the oceanic crust about 10 kilometers deep. As for the Sealand continent, the crust only extends down 20 kilometers because of the extent of stretching. In the end, this extremely thin continent-although not as thin as a normal oceanic crust-sank and disappeared to the bottom of the sea.

Even though the Sealand continent is very thin and submerged by water, geologists are pretty sure that it is a continent because of the various rocks found there. The continental crust is often composed of igneous rocks, metamorphic rocks, and sedimentary rocks, such as granite, schist, and limestone, while the oceanic crust is usually composed of igneous rocks, such as basalt.

However, geologists still have many unsolved mysteries. They are particularly interested in the unusual origins of the Sealand continent and are a little confused. For example, it is not clear how the Sealand continent, which has such a thin crust, is kept together without splitting into smaller “microcontinents.”

Another mystery is when the Sealand mainland was submerged under water, and whether it was once composed of land. The part that is currently above sea level is actually a ridge formed by the compression of the Pacific and Australian plates. Tulloch said that researchers have different opinions on whether the Sealand (except for a few small islands) has been submerged, or it was once a completely dry land.

This also raises a question: What kind of creatures once lived on this continent?

The Gondwana continent has a mild climate and has an active area of ​​101 million square kilometers. It is home to many plants and fauna, including the earliest four-limbed terrestrial animals, and many later giants, such as brontosaurus. So, are the remains of these animals intact in the rocks of the Sealand mainland?

Fossils of land animals are rare in the southern hemisphere, but in the 1990s, people discovered some dinosaur fossils in New Zealand, including a huge long-tailed, long-necked dinosaur (a sauropod ), a kind of beaked herbivorous dinosaur (Prismodon) and ankylosaurus In 2006, researchers discovered the foot bones of a large carnivore (probably an Allosaurus) in the Chatham Islands, about 800 kilometers east of New Zealand’s South Island. Crucially, these fossils can be traced back to the split of Sealand from Gondwana.

However, this does not necessarily mean that the dinosaurs once wandered through most of the Sealand mainland-these islands may have been a refuge for dinosaurs, while other areas were submerged by the sea as they are now. Rupert Sutherland, a geologist at the New Zealand Institute of Geographical Sciences, said: “This issue has been debated for a long time, including whether terrestrial animals are possible in the absence of continuous land, and if there is really no continuous land, whether they Will be extinct.”

Tracing the Lost Continent of 375 Years: There are still many mysteries yet to be solved(1)

This debate It became more complicated with the discovery of one of New Zealand’s most eccentric and beloved residents, the kiwi. This is a stocky, flightless bird with a beak and feathers like hair. Strangely, DNA research shows that the closest relationship with the kiwi is not the moa that has long been thought of, but the elephant bird of Madagascar. Kiwis belong to the order of the wingless birds, elephant birds belong to the order of the moa, and the moa belong to the order of the moa. The kiwi and the moa lived on the same island until the latter became extinct about 500 years ago; the larger elephant bird went extinct about 800 years ago.

This discovery convinced scientists that both the kiwi and elephant bird evolved from a common ancestor living on the continent of Gondwana. It took 130 million years for this supercontinent to completely split. The remaining fragments were scattered all over the world, forming South America, Africa, Madagascar, Antarctica, Australia, the Arabian Peninsula, the Indian subcontinent and the Sealand continent.

This in turn also implies that at least part of the currently submerged Sealand continent has been above sea level, except for about 25 million years ago, the entire continent—and possibly the entire New Zealand— All are thought to have sunk to the bottom of the sea. Sutherland said: “There is a view that all animals and plants moved here later.” So, what happened in the middle?

Although it is impossible to collect fossils directly from the seafloor of Sealand, scientists have been drilling to detect its depth. “In fact, the most useful and unique ones are those fossils formed in very shallow oceans,” Sutherland said, “because they left a record-there may be countless very unique tiny fossils.”</ p>

In 2017, a team conducted the most extensive survey of the area to date, drilling more than 1,250 meters deep into the seabed at 6 different locations. The cores they collected contained pollen, spores of land plants and the shells of creatures living in warm shallow seas.

Sutherland said: “When you find a body of water with a depth of only about 10 meters, there is likely to be land around it.” He explained that pollen and spores also imply that the mainland of Zealand has never been The possibility of being overwhelmed.

The shape of the Sealand mainland is another puzzling puzzle. “If you look at the geological map of New Zealand, you will find two very prominent features,” Sutherland said. One of them is the Alps Fault, which is a plate boundary extending along the South Island. It is very prominent and can be seen from space.

Tracing the Lost Continent of 375 Years: There are still many mysteries yet to be solved(2)

Red Rock The belt was supposed to extend diagonally to the Sealand continent, but it was distorted and deformed

The second feature is that the geological form of New Zealand—and the wider continental geological form—anomaly bending. They are divided into two by a horizontal line, and this horizontal line is the intersection of the Pacific plate and the Australian plate. There seems to be something here that has distorted the lower half of the continent, not only making the previously continuous rock belt no longer connected in a straight line, but even twisting it almost at a right angle.

A simple explanation is that the tectonic plates have moved and deformed in some way. But exactly how and when this happened, scientists still have no way of knowing. “There are various explanations, but this is a rather big unsolved mystery,” Tulloch said.

Sutherland explained that we are unlikely to know all the secrets of the Sealand in the short term. “When everything is 2 kilometers underwater and the rock formation you need to sample is also 500 meters deep below the seabed, it is difficult to find,” he said. “Exploring such a continent is really challenging. It requires A lot of time, money, and effort require ships and survey areas.”

However, the exploration of the eighth largest continent in the world at least shows that nearly 400 years after Tasman’s discovery, this continent still has many orders. People are fascinated.