Scientists talked about the continent hidden under the Pacific Ocean

In the southwestern Pacific Ocean, the continent of Zealand is located with an area of about 4.9 million square kilometers, approximately 94% of which is under water. New Zealand and New Caledonia are the most notable areas of its land. In 2017, geologists presented a scientific justification for the continental status of this territory, and in 2023 they completed its survey geological mapping. Why a huge continent has remained in the shadows for a long time and how scientists are reconstructing its past from samples from the ocean floor — in the Izvestia article.

A continent that is not visible on a regular map

On a familiar world map, New Zealand looks like a group of islands to the southeast of Australia. However, the coastline only shows the boundary between land and water. It does not allow us to see where the continental crust ends and the oceanic crust begins.

If we take into account the geological structure of the region, New Zealand turns out to be part of a much larger territory. Uplands, plateaus and other areas of the continental crust continue underwater, which together with the islands form Zealand.

Its area is about 4.9 million square kilometers. This is a huge geological object, most of which is hidden by the ocean. About 6% of the territory remains above the surface, including New Zealand, New Caledonia and a number of smaller islands.

How scientists define a continent

The authors assessed the territory according to several criteria. It should be elevated relative to the surrounding ocean floor, have a set of igneous, sedimentary and metamorphic rocks characteristic of continents, as well as the corresponding structure of the crust. In addition, dimensions and fairly clear boundaries are important.

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According to the researchers, New Zealand meets these conditions. Its geological structures can be traced on land and under water, and its significant area and separation from Australia make it possible to consider it as an independent continent.

One elevation on the seabed is not enough for such a conclusion. Underwater volcanic plateaus can also rise above the surrounding areas, but this does not make them continents. Scientists needed to compare the relief with the composition of rocks and geophysical data.

What happened in 375 years

According to the historical portal of the Ministry of Culture and Heritage of New Zealand, NZ History, Tasman did not disembark. His voyage was the first documented European sighting of New Zealand, where by that time the Maori already lived.

Indeed, 375 years have passed between the voyage of 1642 and the publication of the geological work of 2017. But these events answered different questions. Navigators described the land they saw, and geologists centuries later established the scale and structure of the continental crust under the surrounding ocean.

The very name Zealandia was proposed by the American geophysicist Bruce Luyendyk back in 1995. Consequently, in 2017, scientists did not name the unknown earth for the first time, but presented detailed arguments in favor of its continental status.

Why is most of Zealand under water?

Zealand was once part of Gondwana, an ancient supercontinent that united the territories of the modern southern continents. During its disintegration, the earth's crust in this region stretched and became thinner. The thinning was accompanied by a sinking of the surface, and significant areas were below sea level.

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The continental crust is usually thicker than the oceanic crust, but its thickness varies from region to region. According to research data, in Zealand it is mostly between 10 and 30 km. Under some parts of the South Island of New Zealand, the thickness exceeds 40 km. Therefore, it is impossible to describe the entire continent as a single layer 20 km thick. Its structure is more complicated: different areas have experienced stretching and subsequent changes to varying degrees.

The dive was also not one sudden event. The appearance of the region has changed over millions of years: sections of the crust have shifted and deformed, and the boundaries of land and sea have changed. The idea of a continent disappearing under water at once simplifies this story.

In a reconstruction presented to GNS Science in 2023, scientists showed changes in the region over almost 100 million years. According to their data, the southern part of Zealand has moved significantly north from the high polar latitudes during this time.

Thus, the near-total immersion of Zealand today does not mean that its entire territory has ever been under water at the same time.

The map is ready, but the research continues

Completing the survey map does not mean that scientists have studied every area of Zealand in detail. Such a map shows large structures and the overall geological picture. New samples, measurements, and more detailed studies are needed to reconstruct individual events.

Of particular importance is the question of how different parts of the continent were deformed during separation from Gondwana. Researchers are also studying the history of magmatism and the origin of structures that are hidden under the ocean today.

The practical value of these works is related to the understanding of geological hazards. New Zealand is located in a region with an active boundary of tectonic plates. The history of faults and volcanic systems helps scientists explain their current behavior.

Paleogeographic maps are also useful for biologists. The shape of the land has changed, so the distribution routes of species in the past were different from the current ones. To restore these movements, you need to know which territories were connected and where the sea barriers were located.