 It runs generally northward, with a length of approximately 500 kilometers (300 miles).The ridge is a section of what remains from the larger Pacific-Farallon Ridge which used to be the primary spreading center of this region, driving the Farallon Plate underneath the North American Plate through the process of plate tectonics.Today, the Juan de Fuca Ridge pushes the Juan de Fuca Plate underneath the North American plate, forming the Cascadia Subduction Zone.