Scientists Found an Ancient Tectonic Plate Buried Deep Inside the Earth's Mantle - ExtremeTech

Plate tectonics — the slow movement of the Earth’s continents across the globe, and their interactions with each other — is a relatively new discovery, having only been broadly accepted in the geologic community since the mid-1960s.

Now, one group studying northwest North America has discovered what it believes are the remnants of a now-vanished plate that slid underneath the Pacific Northwest millions of years ago.

Two of the now-subducted plates underneath this area of the United States and Canada are the Farallon and Kula plates.

A third plate — dubbed Resurrection — has been controversially theorized to exist, with some geologists arguing that it explains certain features of the terrain (and terranes) in particular regions.

“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,” says geologist Jonny Wu, from the University of Houston.

Mountain ranges form at plate boundaries, but they don’t form at anything like a consistent speed.

Understanding where these vanished plates are underneath our feet can aid our understanding of geologic events on the surface, like volcanism.