Because of the very large fault area , the Cascadia subduction zone can produce large earthquakes of magnitude 7.0 or greater . The interface between the Juan de Fuca and North American plates remains locked for periods of roughly 500 years . During these periods , stress builds up on the interface between the plates and causes uplift of the North American margin . When the plate finally slips , the 500 years of stored energy are released in a massive earthquake . The most recent , the 1700 Cascadia earthquake , was recorded in the oral traditions of the First Nations people on Vancouver Island . It caused considerable tremors and a massive tsunami that traveled across the Pacific Ocean . The significant shaking associated with this earthquake demolished houses of the Cowichan Tribes on Vancouver Island and caused several landslides . It also made it too difficult for the Cowichan people to stand , and the tremors were so lengthy that they were sickened . The earthquake-generated tsunami ultimately devastated a winter village at Pachena Bay , killing all the people that lived there . The 1700 Cascadia earthquake caused near-shore subsidence , submerging marshes and forests on the coast that were later buried under more recent debris
1700 Cascadia earthquake
1700 Cascadia earthquake
Canadian Cascade Arc