Earth is a rocky planet, meaning it has an outer layer, known as the lithosphere, which is divided into several rigid plates.
These plates float in the semifluid asthenosphere beneath them. The movement of these plates is a key feature of plate tectonics and a new study now shows that the Pacific plate is moving apart.
Geoscientists at the University of Toronto discovered that the plate is marked by large underwater faults thousands of meters deep and hundreds of kilometers long.
The team was surprised to discover that geological deformation, which is a common feature in the interior of continental plates, also occurs in oceanic plates.
“We knew that geologic deformations, like faulting, occur inside continental plates, far from plate boundaries,” says Erkan Gun, a postdoctoral researcher in the Department of Physical and Environmental Sciences at the University of Toronto in Scarborough. . “But we didn’t know the same thing was happening with oceanic plates.”
The Pacific plate comprises most of the floor of the Pacific Ocean and has been moving westward to sink into the Earth’s mantle along underwater trenches or subduction zones ranging from Japan to New Zealand and Australia. The researchers said that when the western edge of the plate is lowered onto the shelf, it drags the rest of the plate with it like removing a tablecloth from a table.
“It was thought that because the suboceanic plateaus are thicker, they should be stronger,” Gun says. “But our models and seismic data show the opposite: the plateaus are weaker.”
They studied four plateaus in the western Pacific Ocean (Ontong Java, Shatsky, Hess and Manihiki) in a vast area roughly bounded by Hawaii, Japan, New Zealand and Australia.
A supercomputer was then launched to create a model with the existing data that revealed the big changes. The findings of the study have been published in the journal Geophysical Research Letters.
“A new finding like this overturns what we have understood and taught about the active Earth, and shows that radical mysteries still exist even about the great workings of our evolving planet,” Gunn added.