Where it is and what it carries
The Juan de Fuca Plate covers about 256,000 square kilometers, or 0.05% of Earth’s surface. It lies off the coasts of northern California, Oregon, Washington and Vancouver Island in Canada, and it is made entirely of oceanic crust. No country has land on it.
In the PB2002 model, the plate includes the Gorda section in the south and the area off northern Vancouver Island in the north. Some geologists split these off as separate Gorda and Explorer microplates, because the seafloor there deforms internally and moves a little differently from the main plate.
What happens at its edges
On its western side, the plate spreads away from the Pacific Plate at about 5.6 cm/yr. The boundary is a series of ridge segments, including the Juan de Fuca Ridge and the Gorda Ridge, offset by transform faults such as the Blanco Fracture Zone.
On its eastern side, the plate sinks beneath the North American Plate along the 1,415 km Cascadia Subduction Zone, at about 4 cm/yr. The fault stretches from Cape Mendocino in California to Vancouver Island. Its southern end is the Mendocino Triple Junction, where the Juan de Fuca, Pacific and North American plates meet and the San Andreas Fault begins.
Earthquakes and volcanoes
The Cascadia Subduction Zone is quiet today, but it is locked rather than inactive. Geological and historical evidence shows it last ruptured in a great earthquake in January 1700, and earlier great quakes are recorded in coastal sediments.
The dataset lists 29 earthquakes of magnitude 6.5 or larger on the plate itself since 1900, mostly offshore near its edges. The largest was an M7.48 event in 1929 west of Vancouver Island. Several strong quakes have struck offshore northern California near Cape Mendocino, including an M7.2 in 2005 and an M7.0 in December 2024 that prompted a tsunami warning.
The plate holds eight volcanoes in the dataset, all on its spreading ridges. Axial Seamount, far off the Oregon coast, last erupted in 2015 and is one of the most closely monitored submarine volcanoes in the world. On land, the plate’s subduction feeds the Cascade Range on the North American Plate, including Mount St. Helens, which erupted in 1980.