 The Insular Plate continued to subduct under the new continental shelf and coastline about 130 million years ago during the mid Cretaceous period after the formation of the Intermontane Belt, supporting a new continental volcanic arc called the Omineca Arc.Magma rising from the Omineca Arc successfully connected the Intermontane Belt to the mainland of North America, forming a chain of volcanoes from Washington to British Columbia that existed for about 60 million years.The ocean lying offshore during this period is called the Bridge River Ocean.