Geologists “revive” a missing tectonic plate in northern Canada

On the way back to the early Cenozoic about 40 to 60 million years ago, there were two large tectonic plates in the Pacific Ocean off the west coast of North America – Kula and Farallon. These two tectonic plates are at the center of geologists’ debate over whether the two plates were strangely connected by a third plate called the Resurrection, which would have peeled off and moved sideways and down into the Earth’s mantle, Science Daily reports.

A team of geologists at the University of Houston (UH) College of Science and Mathematics believe they found the lost plate in northern Canada and published their results in the bulletin of the Geological Society of America. The team consists of Jonny Wu, Assistant Professor of Geology in the Department of Earth and Atmospheric Sciences, and Spencer Fuston, a third-year PhD student in geology. The two scientists used a technique called plate unfolding, developed by the UH Center for Tectonics and Tomography, to reconstruct what tectonic plates looked like in the early Cenozoic Pacific.

We know that when the Earth’s plates press against each other, one of them often sinks below the other plate when they move, a process called subduction. Regions where this process takes place are called subduction zones. These zones are locations with usually high volcanic and earthquake rates. The Resurrection Plate is believed to have formed a special type of volcanic belt along Alaska and Washington State. To find out what was left of the resurrection plate, the team first examined existing tomography images of the mantle under North America. To prove their theory, Wu and Fuston applied the unfolding technique to the mantle tomography images and pulled out each of the subducted plates before they were unfolded and stretched to their original shape.

Using this technique, the team found several large boulders and worked backwards to identify the original slabs they were from. Two of the objects are already known to science – the Alaska and Cascadia plates, and they’re still connected, New Atlas reports. The Alaska Plate is located under the Aleutian Islands and is believed to be a holdover from the Kula Plate. The Cascadia Plate lies under Southern California and is considered the remaining part of the Farallon Plate. There was a third object that the team found, and it was cut off from the others, about 400 to 600 kilometers below the surface of northern Canada. They call it the Yukon Plate, and when the clock is turned back it appears to conform to the calculated shape of the ancient Resurrection Plate. “When the boundaries of this ancient tectonic plate of the resurrection are raised back to the surface and reconstructed, they will fit well with the ancient volcanic belts in Washington state and Alaska and provide a coveted connection between the ancient Pacific and the North American geological record”, explained Wu.