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Much of the rocks that underlie British Columbia formed elsewhere and were transported here in the distant geological past. The margin of the North American continent has grown westward from the Alberta border by the addition of exotic fragments of the Earth's crust, which geologists call 'terranes'. Wrangellia Terrane, which forms most of Vancouver Island, originated within what is now the Pacific Ocean and was transported northeasterly to collide with North America about 100 million years ago. The force of this collision crumpled North American rocks as far to the east as the Rocky Mountains.

Vancouver Island experiences frequent earthquakes because it is close to the western margin of the North America Plate. The oceanic Juan de Fuca Plate dives down into the Earth's mantle beneath Vancouver Island, creating the stresses that are responsible for earthquakes. Damaging earthquakes on Vancouver Island can occur within the North America Plate, much deeper within the Juan de Fuca Plate, or at the boundary between these two plates.