Kula plate

[1] As the name suggests, the Kula plate was entirely subducted around 48 Ma and today only a slab in the mantle under the Bering Sea remains.

[3][4] The Kula plate began subducting under the Pacific Northwest region of North America during the Late Cretaceous period much like the Pacific plate does today, supporting a large volcanic arc system from northern Washington to southwestern Yukon called the Coast Range Arc.

About 55 million years ago, the Kula plate began an even more northerly motion.

Riding on the Kula plate was the Pacific Rim Terrane consisting of volcanic and sedimentary rock.

It was scraped off and plastered against the continental margin, forming what is today Vancouver Island.