Plate tectonics, while now the dominant theory, accepts that it is long and rugged, describing how much of the Earth's crust slowly slides, grinds, rises, and sinks in its muddy mantle.
But even now, more than half a century after the theory was scientifically validated, the theory still needs some refinement.
A new study of four plateaus in the western Pacific shows that these vast areas are not rigid plates, but weak points pulled apart by distant forces at the edge of the plates.
Russell Pysklywec, a geophysicist at the University of Toronto and co-author of the study, said: "This theory is not set in stone, and we are still looking for something new. ”。
Lead author Erkan Gün, a geoscientist at the University of Toronto, added: "We know that geological deformations, such as faults, occur in the interior of continental plates, far from plate boundaries. But we didn't know that the same thing happened with the ocean plate. ”。
Scientists have been rewriting their understanding of the ocean floor for decades, so this new study is just a continuous process of mapping the ocean's rugged topography.
In the 50s of the 20th century, marine cartographer Marie Tharp's pioneering work in mapping much of the ocean floor using sonar data showed that ocean basins are not as flat surfaces as scientists suspect.
Instead, the seafloor is divided by cracked trenches and massive mountain ranges – none larger than the Mid-Atlantic Ridge discovered by Talp, now considered the longest mountain range on Earth, bisecting the Atlantic Ocean.
Such mountains are formed when two tectonic plates collide, the earth's crust bends, or one plate sinks below the other, pushing the overfilled plate upwards. Underwater, however, seamounts are usually formed by the drift of two tectonic plates at the so-called divergent boundary, with magma erupting.
But in the center of the oceanic plates, far from these plate boundaries, scientists believe that when much of the crust drifts on the top of the mantle, they remain fairly hard and do not deform like plate edges.
To test this idea, Gün, Pysklywec, and colleagues collected available data on two oceanic plateaus located between Japan and Hawaii, known as the Shatsky Seamount and the Hess Seamount; the Ontun Java Plateau in the northern Solomon Islands; and the Manihiki Plateau in Fiji and northeastern Tonga.
Given the challenges of seabed surveys, their research was limited to the four plateaus for which data were available in the western Pacific Ocean.
A map of the Pacific tectonic plates highlights four oceanic plateaus and their margins.
Faults in the four oceanic plateaus of the Pacific Plate (indicated by short, thick black lines) tend to be parallel to the nearest plate boundary (subduction gully). （gün et al.，geophys.res.let，2024）
The oceanic plateau is located hundreds to thousands of kilometers away from the nearest plate boundary. However, Gün and colleagues found that these plateaus share common deformation and magmatic characteristics, suggesting that they are being torn apart by the tension of the Pacific plate margin, where the plates are subducting beneath adjacent plates.
As you can see on the map above, the faults or fault lines found by the researchers tend to run parallel to the nearest trenches.
The team also modeled the tectonic plate dynamics of four hypothetical plateaus 750 to 1,500 km (466 to 932 mi) from the nearest subduction zone to better understand the mechanisms that led to this distant deformation.
Schematic diagram showing weak points in an ocean plate stretched by subduction at the edge of the plate.
The team's modelling results suggest that oceanic plateaus are weak points in the Earth's crust that are stretched when the edges of tectonic plates are pulled downward (subducted) at distant ocean trenches. （gün et al.，geophys.res.let，2024）
Regardless of their distance from the plate margin, these hypothetical plateaus extend over millions of years, becoming thinner on the side closest to the trench.
"It is believed that since the sub-oceanic plateau is thicker, they should be stronger," Gün said. ”。But our models and ** data suggest that the opposite is true: the plateau is weaker. ”
The researchers admit they have only analyzed four Pacific plateaus in the hope that their findings will spur further seafloor exploration.
Sending a research vessel to collect data is a major effort," said Gün. "So, in fact, we hope that our ** will draw attention to the plateau and collect more data. ”
The study was published in Geophysical Research Letters.