Journey Through Geological History: Ancient Mega-Plate Resurfaces After 20 Million Years

Journey Through Geological History: Ancient Mega-Plate Resurfaces After 20 Million Years
Image by (Mark Garlick/Science Photo Library/Getty Images)

During recent geological research, a surprising discovery has revealed the existence of a long-lost tectonic plate in the South China Sea region. Researchers have managed to locate this plate, known as the "Pontus Plate," after 20 million years of scientific disappearance. 

Known only from a few rock fragments in the mountains of Borneo and large remnants detected in the Earth's mantle, the plate was once the size of a quarter of the Pacific Ocean. The discovery surprised scientists and sparked a deep interest in the region's geological history.

According to Live Science, Suzanna van de Lagemaat, a doctoral candidate at Utrecht University in the Netherlands, initially focused her and her colleagues' research on Pacific plate tectonics at the bottom of the Pacific Ocean. These tectonic plates move relative to each other, with the crust beneath the oceanic plates having a higher density than the continental plates, so the oceanic plates tend to be pushed beneath the continental plates in a process known as subduction and eventually disappear. 

Sometimes, however, rocks from the disappearing plate can be involved in the formation of mountain ranges. These remnants have the potential to reveal the location and history of ancient plate tectonics.

During fieldwork in Borneo, the research team attempted to locate the remains of one of the ancient vanished plates, known as the Phoenix Plate. Van de Lagemaat points out that scientists use the magnetic properties of rocks to determine when and where they were formed. He explained that the magnetic field surrounding the Earth is actually "locked in" at the time of rock formation, and the characteristics of that magnetic field can vary depending on latitude.

While analyzing the rocks collected in Borneo, the researchers discovered an unusual phenomenon. Suzanna van de Lagemaat showed that the latitudes found in the analysis did not match the latitudes normally associated with previously known plates.

To explain this, Suzanna van de Lagemaat used a computer model that explored the geological history of the region over the past 160 million years. The reconstruction of plate movements revealed a significant shift between what is now South China and Borneo. The ocean once thought to be underlain by an ancient plate called the Izanagi Plate, no longer sits on top of it. Instead, rocks from Borneo have filled the mysterious gap.

Fragments of the Pontus plate, believed to have been present around 120 million years in the past, have been discovered in the northern part of Borneo. Image by Utrecht University

The research revealed that the area was actually occupied by a previously unknown plate, and the team led by van de Lagemaat named it the Pontus Plate.

The results of this reconstruction, published on September 29 in the journal Gondwana Research, show that the Pontus Plate formed at least 160 million years ago, although its actual age may be older. The plate was once enormous, but it continued to shrink over time, eventually sliding under the Australian plate to the south and the Chinese plate to the north until it disappeared about 20 million years ago.

A decade of research in the same lab also provided important clues to the existence of the Pontus plate. The research looked at the Earth's middle layer, called the mantle, where the subducted crust ends. 

At the time, van de Lagemaat explained that scientists had no way of determining the origin of these plates. However, it is now clear that the crust is a remnant of the Pontus P late.

Source: Live Science

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