A previously unknown ancient tectonic plate has been discovered, extending from Japan to New Zealand. The revelation comes from the research of Suzanna van de Lagemaat, a PhD geology student at Utrecht University.

Unearthing the Past in Borneo

The remarkable identification of this large quarter-Pacific-sized ancient tectonic plate was made through samples collected in Borneo/Kalimantan. These plates are hidden beneath the Earth’s surface, and when they move, larger oceanic plates can descend beneath them, a process known as “subduction.” While most of these plates remain concealed, remnants can be found in underwater mountain ranges where tectonic plates shift and molten rock erupts to create seamounts.

Enormous Ancient Plate

Van de Lagemaat focused her research on the Philippines, a region prone to such volcanic eruptions.

Complex Plate Intersections

The Philippines sits at a complex intersection of various tectonic plate systems. Van de Lagemaat explained, “This area is almost entirely oceanic crust, but some areas are above sea level and exhibit rocks with very different ages.”

Studying geological data, van de Lagemaat reconstructed the movement of plates between Japan and New Zealand, leading her to the conclusion that the ancient plate she identified must have been extremely vast before its eventual disappearance.

Stretching from Japan to New Zealand

Eleven years ago, a team examining seismic data in the area discovered signal disruptions caused by seismic waves passing through submerged tectonic plates. This allowed the team to pinpoint the presence of an ancient subduction zone.

Van de Lagemaat and her team then studied the samples collected in Kalimantan. To their surprise, they found that the samples did not match any known tectonic plates.

A Mysterious Plate Emerges

“We initially thought we were dealing with remnants of a known lost plate,” van de Lagemaat revealed. “However, our magnetic laboratory research on the rocks showed that our findings must have come from far to the north, representing a previously unknown plate.”

Her research estimated that this ancient plate, now named Pontus, extended from southern Japan to New Zealand for about 150 million years. The remnants of this ancient plate are located in the western Philippines on Palawan Island and in the South China Sea.

Conclusion

The research team was surprised that they already had these rock samples in their possession. “Eleven years ago, we thought the remnants of Pontus might be in northern Japan, but we ruled out that theory,” said Douwe van Hinsbergen, van de Lagemaat’s supervisor.

It wasn’t until Suzanna systematically reconstructed half of the Circum-Pacific orogenic belt from Japan through Papua New Guinea to New Zealand that the existence of the Pontus plate was unveiled, including the rocks they had studied in Kalimantan.

This discovery opens new windows into Earth’s geological history and adds to our understanding of the complex processes beneath the planet’s surface.