The Cascadia subduction zone (also referred to as the Cascadia fault) is a convergent plate boundary that stretches from northern Vancouver Island to northern California. It is a very long sloping subduction zone fault that separates the Juan de Fuca and North America plates. The denser oceanic plate is subducting beneath the less dense continental plate offshore of British Columbia, Washington and Oregon. The North American Plate moves in a general southwest direction, overriding the oceanic plate.