This cycle of growth and dormancy strings together volcanoes over millions of years, leaving a trail of volcanic mountains and intrusions extending from coastal British Columbia across the Coast Mountains into the Interior Plateau. According to Wilson's theory, the Anahim volcanoes should be progressively older and increasingly eroded the further they are from the hotspot and this is easily observable; the oldest rock on coastal British Columbia, that of the Gale Passage dike swarm, is about 14.5 million years old and deeply eroded, while the rock at Nazko Cone, the hotspot's present centre, is a comparatively young 0.34 million years of age or less. Radiocarbon dating of peat directly above and below a tephra layer extending from Nazko Cone suggest that the latest eruption occurred approximately 7,200 years ago.