 As the last of the Kula Plate decayed and the Farallon Plate advanced back into this area from the south, it once again started to subduct under the continental margin of Western Canada 37 million years ago, supporting a chain of volcanoes called the Cascade Volcanic Arc.At least four volcanic formations along the British Columbia Coast are associated with Cascadia subduction zone volcanism.The oldest is the eroded 18-million-year-old Pemberton Volcanic Belt which extends west-northwest from south-central British Columbia to the Queen Charlotte Islands in the northeast where it lies west of mainland British Columbia.