Introduction
In 1820, the passengers of a Russian ship saw on the horizon a huge iceberg covered with penguins in a strange way. This was the first sight of the Fimbul Ice Shelf. That is, from there, the official discovery of a new continent, Antarctica, began.
The Earth is home to seven recognized continents, each with its unique geological history and characteristics. However, there exists an intriguing yet relatively unknown eighth continent called Zealandia. Zealandia is not just a small landmass but a vast submerged continental mass beneath the southwestern Pacific Ocean. In this blog post, we'll delve into the fascinating story of how Zealandia, the eighth continent of the Earth, was formed and eventually sunk beneath the ocean's surface.
This further strengthened the modern idea that the earth was divided into seven major regions. Most maps of the English-speaking world acknowledged the existence of Antarctica before its discovery.
How long Formation of Zealandia ?
Zealandia wasn't always hidden beneath the ocean. It has a long and complex geological history that stretches back hundreds of millions of years. The formation of Zealandia can be traced back to the breakup of the supercontinent Gondwana, which began around 85 million years ago during the Late Cretaceous period.
Are The Gondwana Breakup:
Zealandia was once part of the supercontinent Gondwana, which included present-day South America, Africa, Antarctica, Australia, the Indian subcontinent, and Zealandia.
Around 85 million years ago, tectonic forces started to pull Gondwana apart, causing Zealandia to separate from Antarctica and Australia.
Continental Drift:
As Zealandia drifted away from Gondwana, it began to move eastward, gradually sinking beneath the ocean's surface.
During this drift, Zealandia underwent various geological processes, including volcanic activity and the deposition of sediments.
Plate Tectonics:
Zealandia's position is largely influenced by tectonic plate movements. It sits atop two major tectonic plates: the Pacific Plate and the Australian Plate.
The boundary between these plates is known as the "Zealandia Fault Zone." It plays a crucial role in the continent's geological activity.
Today, school students, explorers, leaders and even common people have accepted the division of the Earth's land into these simple units, under which the Earth's land is divided into seven continents namely Asia, Europe, Africa, North America, South America, Australia and Antarctica.
The Eight continents predicted 375 years ago
However, in 2017, the story took an unexpected turn, suggesting that the seven-continent model has always been a mistake. Zealandia, a long-lost piece of land in the south-east of Australia, took everyone by surprise.
Zealandia is considered as the eighth forgotten continent of the earth. Scientists had long ago predicted this unknown southern land. But it disappeared for 375 years, as it is almost completely submerged 1 to 2 km below the water. Now scientists have begun to lift the veil of mystery in it.
The scientist released the map of Zealandia
This month, an international group of researchers released the most accurate map of Zealandia ever. It includes all 5 million square kilometers of underwater area and its geology. In this process, scientists have also tried to find out the secret of how the mysterious continent was formed and why it has been hiding under the sea for the last two and a half million years.
Zealandia was formed 80 million years ago
According to scientists, this eighth continent was formed about 83 million years ago in the late Cretaceous period. However, its journey began 100 million years ago when the Gondwana continent began to break up. At that time, the Gondwana continent covered most of today's land in one huge area.
With the disintegration of Gondwana, the smallest, thinnest and youngest continent of the earth destroyed itself, and the areas in the northwest and southwest of Gondwana became Australia and Antarctica respectively.
Zealandia was submerged in the sea two and a half million years ago
According to scientists, all or part of Zealandia may have existed as an island for some time. However, about 25 million years ago, it sank under the sea and disappeared. The first real sign of this could be New Zealand's seemingly tiny part of a vast secret landmass.
It was first revealed in 2022, when scientists used bathymetry, or the depth under water, to analyze the area. The plot thus found was called Zealandia.
The ocean above Zealandia is much shallower than the surrounding oceans. What has been discovered from this is that this area was not under a marine tectonic plate like most of the oceans on Earth, but a continental area.
However, a decisive fact came in 2017 on this matter. In that sequence, the scientists submitted various pieces of evidence, including data on the type of rock it contained and its relative thickness.
Oceanic plates are thin, while Zealandia is very thick. That fact also strengthened the argument that Zealandia was a new continent. It is not just a continental fragment or sub-continent but a real continent and 95 percent of it is submerged in water.
However, despite the excitement over the discovery of a new continent and more than a decade of intensive research, many details of Zealandia's early formation remain unclear. This was partly the result of a mysterious event that occurred during the separation from Gondwana.
Why did Zealandia sink?
In 2019, an international team of scientists mapped the geology of South Zealand. What was discovered from the said research was that Zealandia collapsed at some point. In other words, the force of the tectonic plate separated him. This caused the continent of Zealandia to become thinner than the regular continental plates and created rifts that later turned into oceanic plates.
In this process, the continent of Zealandia was deformed, making it difficult to reorganize its history and its original form. While the researchers analyzed the rocks of this continent, it was discovered that the breakup occurred in two stages. It first started about 89 to 101 million years ago. This created a rift that formed the Tasman Sea between Australia and New Zealand.
The second phase began 8 to 90 million years ago and resulted in the separation of Zealandia from West Antarctica and the formation of the Pacific Ocean.
Scientists this time investigated rocks that were extracted from the Fairway Ridge in the South Pacific, off the coast of Australia, which is the northernmost tip of Zealandia.
The ancient remains, which have not been dry for a single day for 2.5 million years, contain a mixture of igneous rocks that are formed by volcanic processes. The scientists analyzed the chemistry and radioactive isotopes of those rocks in depth and estimated the age and origin of the rocks.
The most complete rock found in that sequence was the early Cretaceous period, that is, about 130 million to 110 million years old. Similarly, 95 million years old Late Cretaceous period sandstone as well as 40 million years old Eocene period relatively new basalt rock has also been found there.
Submersion of Zealandia
Zealandia's submersion into the ocean was a gradual process that occurred over millions of years. Several factors contributed to its sinking:
Isostatic Adjustment:
Isostatic adjustment is the process by which Earth's crust responds to changes in the distribution of weight on its surface.
As Zealandia moved away from the Gondwana supercontinent, its crust began to thin and sink, causing the continent to gradually submerge.
Rising Sea Levels:
Over time, global sea levels have fluctuated due to various factors such as climate change and glacial cycles.
Rising sea levels played a significant role in Zealandia's submersion, covering more and more of its landmass.
Tectonic Activity:
The ongoing tectonic activity in the region, including subduction zones and seismic activity, also contributed to Zealandia's descent below the ocean's surface.
Modern Understanding of Zealandia
In recent years, Zealandia has gained recognition as a distinct continent. Scientists have used various geological and geophysical evidence, including bathymetric maps and seismic data, to support its classification as a continent. This recognition is essential not only for scientific understanding but also for the conservation and exploration of this unique underwater landmass.
Conclusion
Zealandia, the eighth continent of the Earth, is a testament to the dynamic nature of our planet's geology. Formed through the breakup of Gondwana and subjected to the forces of plate tectonics and rising sea levels, Zealandia now lies hidden beneath the ocean's surface. Its story continues to unfold as scientists uncover more about its geological history and significance, reminding us of the ever-evolving nature of our planet. Zealandia stands as a testament to the ongoing processes that shape the Earth's surface, both above and below the waves.
