Farallon plate fragmentation (Cretaceous–Cenozoic)
The enormous Farallon plate, which once covered much of the eastern Pacific, broke into the Juan de Fuca, Cocos, and Nazca plates as the Pacific-Farallon ridge approached the North American trench. Geologists have found fossil microplates it left behind.
New plate boundaries formed as segments detached at different times.
The fragments became today's active oceanic plates, including the one now tearing apart off Vancouver Island.
The paper cites these fossil microplates as evidence that subduction systems break apart in pieces. Cascadia now shows the process happening live.
