The Pontus tectonic plate, one-quarter the size of the Pacific Ocean, was discovered by accident when scientists studied ancient rocks in Borneo.
Location of the Pontus tectonic plate. Image: Suzanna van de Lagemaat
A long-lost tectonic plate that once lay beneath the East Sea was rediscovered 20 million years after its disappearance. Pontus is known only from a few pieces of rock on the mountains of Borneo and giant rock fragments discovered deep within the Earth's mantle. It was once one-quarter the size of the Pacific Ocean. Scientists named it the Pontus plate because at the time of its existence, it was located under the ocean of the same name, Space reported on April 16.
Suzanna van de Lagemaat, a doctoral student at Utrecht University in the Netherlands, and her colleagues initially studied the Pacific plate below this ocean. Tectonic plates constantly move relative to each other, and the crust on marine tectonic plates is denser than on continental plates, so they are pushed below the continental plates in a process called subduction and disappear. . However, sometimes, rocks from the lost plate get mixed into the mountain building movement. They can reveal the location and formation process of ancient tectonic plates.
The team attempted to find one of the lost ancient tectonic plates called the Phoenix plate during field work in Borneo. Scientists can look at the magnetic characteristics of rocks to find out when and where they were born. The magnetic field surrounding the Earth is recorded in rocks and varies with latitude. But the team discovered something strange when analyzing rocks collected in Borneo: the latitude did not match the data they obtained from other known tectonic plates.
To uncover the mystery, Lagemaat used computer modeling to understand the region's geology over the past 160 million years. The process of reconstructing the tectonic plate shows that lying beneath the ocean separating Borneo and the East Sea today is not the ancient Izanagi tectonic plate but a new, unknown plate. Lagemaat and colleagues call this the Pontus plate.
The reconstruction published in the journal Gondwana Research shows that the Pontus plate formed at least 160 million years ago but may be older. It once had a huge size but gradually shrank, eventually being pushed under the Australian plate and disappearing 20 million years ago. Its remnants are a giant piece of crust in the Earth's middle layer.
An Khang (Follow Space)
