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article imageGeologists 'resurrect' missing tectonic plate in Northern Canada

By Karen Graham     Oct 21, 2020 in Technology
A tectonic plate called the Resurrection Plate has long been a topic of debate among geologists, with some arguing it was never real, while others say it subducted down into the Earth's mantle millions of years ago. Geologists believe they have found it.
Going way, way back to the early Cenozoic Era, around 40 to 60 million years ago, there were two major tectonic plates - called the Kula and the Farallon - in the Pacific Ocean off the western coast of North America.
These two tectonic plates are at the center of debate by geologists over whether the two plates were joined by a third plate, strangely enough, called Resurrection, which would have subducted, moving sideways and downward into the planet's mantle, reports Science Daily.
Plate distribution between 64 and 74 million years ago. Arrows represent direction of subduction alo...
Plate distribution between 64 and 74 million years ago. Arrows represent direction of subduction along North America.
Black Tusk
A team of geologists at the University of Houston (UH) College of Natural Sciences and Mathematics believes they have found the lost plate in northern Canada and they have published their findings in the Geological Society of America Bulletin.
The team consists of Jonny Wu, assistant professor of geology in the Department of Earth and Atmospheric Sciences, and Spencer Fuston, a third-year geology doctoral student. The two scientists applied a technique developed by the UH Center for Tectonics and Tomography called slab unfolding to reconstruct what tectonic plates in the Pacific Ocean looked like during the early Cenozoic Era.
Diagram of the geological process of subduction
Diagram of the geological process of subduction
"Subduction-en.svg from Wikimedia Commons by K. D. Schroeder
We know that when the Earth's plates push against each other, one of them will often sink under the other plate as they move, a process called subduction. Regions where this process occurs, are known as subduction zones. These zones are sites that usually have a high rate of volcanism and earthquakes.
The Resurrection plate is believed to have formed a special type of volcanic belt along Alaska and Washington State. To try to find what was left of the Resurrection plate, the team began by studying existing tomography images of the mantle below North America.
To prove their theory, Wu and Fuston applied the unfolding technique to the mantle tomography images - pulling each of the subducted plates out before unfolding and stretching them to their original shapes.
A 3D block diagram across North America showing a mantle tomography image reveals the slab unfolding...
A 3D block diagram across North America showing a mantle tomography image reveals the slab unfolding method used to flatten the furlone tectonic plate. In doing so, Faston and Wu were able to locate the lost resurrection plate.
Spencer Faston, Johnny Woo, University of Houston, College of Natural Sciences, Earth and Atmospheri
Using the technique, the team found several large chunks of rock and worked backward to identify the original plates they came from. Two of the objects are already known to science - the Alaska and Cascadia slabs, and they are still attached to each other, reports New Atlas.
The Alaska slab sits beneath the Aleutian Islands and is believed to be a remnant of the Kula plate. The Cascadia slab lies beneath Southern California and is thought to be a remaining part of the Farallon plate.
There was a third object the team found, and it was detached from the others, about 400 to 600 kilometers (250 to 370 miles) below the surface of Northern Canada. They call it the Yukon Slab, and when the clock is wound back it appears to fit the calculated shape of the old Resurrection plate.
"When 'raised' back to the earth's surface and reconstructed, the boundaries of this ancient Resurrection tectonic plate match well with the ancient volcanic belts in Washington State and Alaska, providing a much sought after link between the ancient Pacific Ocean and the North American geologic record," explained Wu.
More about Resurrection plate, Northern Canada, mantle tomography images, Cenozoic period, 3D mapping technology
 
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