Earth's Tectonic Plates are, Surprisingly, Not As Rigid as Previously Thought

It turns out that the tectonic plates aren't as rigid as we first thought. Scientists have found that these puzzle pieces that make up Earth's crust actually flex and bend, challenging the notion that the plates are stiff and unyielding.

In order to better understand the tectonic place, the scientists used large-scale numerical modeling as well as GPS velocities from the largest GPS data-processing center in the world. This revealed that the cooling of the lithosphere, the outermost layer of Earth, causes some sections of the Pacific plate to contract horizontally at faster rates than other sections. This causes the plate to deform.

In fact, the results reveal that plate-scale horizontal thermal contraction is significant, and may be partly released seismically.

"This is plate tectonics 2.0, it revolutionizes the concepts of plate rigidity," said Corne Kreemer, one of the researchers, in a news release. "We have shown that the Pacific plate deforms, that it is pliable. We are refining the plate tectonic theory and have come up with an explanation for mid-plate seismicity."

The oceanic plates are shortening due to cooling, which causes relative motion inside the plate. The oceanic crust of the Pacific plate off shore California is moving about 2 mm to the south every year relative to the Pacific/Antarctic plate boundary.

"It may not sound like much, but it is significant considering that we can measure crustal motion with GPS within a fraction of a millimeter per year," said Kreemer. "Unfortunately, all existing GPS stations on Pacific islands are in the old part of the plate that is not expected nor shown to deform. New measurements will be needed within the young parts of the plate to confirm this study's predictions, either on very remote islands or through sensors on the ocean floor."

The findings reveal a bit more about the tectonic plates, and may actually help with earthquake prediction. By quantifying the deformation in all of Earth's plate boundary zones with GPS velocities, scientists could convert the strain rates to earthquake forecast maps.

The findings are published in the journal Geology.