Plate tectonics is currently the prevailing theory that describes how large portions of Earth’s crust move across its sludgy mantle, but it faced a long and bumpy road to acceptance. Widespread extensional deformation during plate drift is indicated by geological and geophysical evidence from the Pacific plate. Despite being given the scientific tick of approval over half a century ago, the theory still requires refinement.
A recent study focusing on four plateaus in the western Pacific Ocean indicates that these expansive areas are not rigid slabs but rather weak spots being pulled apart by distant forces at the edge of the plate.
“The theory’s not carved in stone and we’re still finding new things,” says University of Toronto geophysicist Russell Pysklywec, who co-authored the study.
“We knew that geological deformations like faults happen on the continental plate interiors far from plate boundaries. But we didn’t know the same thing was happening to ocean plates,” adds first author Erkan Gün, also an earth scientist at the University of Toronto.
Scientists have been studying the seafloor for decades, and this new study is a continuation of their efforts to chart the ocean’s topography. In the 1950s, Marie Tharp used sonar data from warships to map large parts of the seafloor and discovered that it was not a flat surface, but instead had trenches and mountains. The
Mid-Atlantic Ridge, which Tharp discovered, is now recognized as the longest mountain range on the planet.
Submarine mountains usually form when two tectonic plates drift apart at a divergent boundary and magma spews out. However, far from these plate boundaries, scientists previously thought that large sections of Earth’s crust remained fairly rigid as they drifted atop the mantle and did not deform like plate edges.
To test this thinking, Gün, Pysklywec, and colleagues gathered existing data on four oceanic plateaus located hundreds to thousands of kilometers from the nearest plate boundary. The study was limited to the Shatsky Rise and Hess Rise between Japan and Hawaii, the Ontong Java Plateau north of the Solomon Islands, and the Manihiki Plateau northeast of Fiji and Tonga because of the challenges in surveying the seafloor.
The team found that these plateaus shared deformational and magmatic features that suggest they are being torn apart by pull forces at the Pacific plate’s edge, where slabs are being subducted underneath neighboring plates. The ruptures or fault lines identified by the researchers tend to run parallel to the closest trench.
The team also modeled tectonic plate dynamics for four hypothetical plateaus located between 750 and 1,500 kilometers from the nearest subduction zone to understand the mechanisms giving rise to this distant deformation. These hypothetical plateaus were stretched and thinned over millions of years, regardless of their distance from the plate edge, with the side closest to the trench being more affected.
“It was thought that because the sub-oceanic plateaus are thicker, they should be stronger,” Gün says. “But our models and seismic data show it’s actually the opposite: the plateaus are weaker.”
Acknowledging that they only analyzed four Pacific plateaus, the researchers hope that their findings will encourage further explorations to map the seafloor.
“Sending research vessels to collect data is a major effort,” Gün says. “So, in fact, we’re hopeful our paper brings some attention to the plateaus and more data will be collected.”
This news is a creative derivative product from articles published in famous peer-reviewed journals and Govt reports:
References:
1. Gün, Erkan, et al. “Syn‐Drift Plate Tectonics.” Geophysical Research Letters 51.2 (2024): e2023GL105452.
2. Ai, H. A., Stock, J. M., Clayton, R., & Luyendyk, B. (2008). Vertical tectonics of the High Plateau region, Manihiki Plateau, Western Pacific, from seismic stratigraphy. Marine Geophysical Researches, 29(1), 13–26. https://doi.org/10.1007/s11001-008-9042-0
3. Estep, J., Reece, R., Kardell, D. A., Perez, N. D., Christeson, G. L., & Carlson, R. L. (2020). Intraplate deformation of oceanic crust near the Rio Grande Rise in the South Atlantic. Tectonophysics, 790, 228543. https://doi.org/10.1016/j.tecto.2020.228543
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