Insular Plate

Ancient oceanic plate

The Insular Plate was an ancient oceanic plate that began subducting under the west-coast of North America around the early Cretaceous period. The Insular Plate had a chain of active volcanic islands that were called the Insular Islands. These volcanic islands, however, collided then fused onto the west-coast of North America when the Insular Plate jammed then shut down ending the subduction zone.^[1]

References

^ Townsend, Catherine L.; Figge, John T. (2002). "The Coast Range Episode". Northwest Origins: An Introduction to the Geologic History of Washington State. The Burke Museum of Natural History and Culture, University of Washington. Retrieved 12 August 2019.