 The ridge is a medium rate spreading center, moving outwards at a rate of approximately 6 centimeters per year.Tectonic activity along the ridge is monitored primarily with the U.S. Navy's Sound Surveillance System (SOSUS) array of hydrophones, allowing for real time detection of earthquakes and eruptive events.The Juan de Fuca Plate is being pushed east underneath the North American Plate, forming what is known as the Cascadia subduction zone off the coast of the Pacific Northwest.