 The Insular Belt then welded onto the continental margin by magma that eventually cooled to create a large mass of igneous rock, creating a new continental margin.This large mass of igneous rock is the largest granite outcropping in North America.The Farallon Plate continued to subduct under the new continental margin of Western Canada after the Insular Plate and Insular Islands collided with the former continental margin, supporting a new chain of volcanoes on the mainland of Western Canada called the Coast Range Arc about 100 million years ago during the Late Cretaceous epoch.