Juan de Fuca Plate
The Juan de Fuca Plate is the 38th-largest of the 52 plates in the PB2002 plate model, covering 257,000 km² (99,000 sq mi), or 0.1% of Earth’s surface. The ocean floor off Oregon, Washington and British Columbia.
- Area
- 257,000 km² (99,000 sq mi)
- Share of Earth’s surface
- 0.1%
- Speed across the plate
- 1.5 to 2.8 cm a year (0.6 to 1.1 in)
- Direction at its center
- Toward the east-northeast
- Length of its edges
- 3,310 km (2,060 mi)
- Neighboring plates
- 2
- Edges by type
- 43% convergent · 32% divergent · 25% transform
- Volcanoes on it
- 8 active in the past ~12,000 years
What happens at its edges
It sinks beneath North America at the Cascadia subduction zone. That boundary feeds the Cascade volcanoes and produced a magnitude-9 earthquake in January 1700, known from Native American oral history, drowned forests and a tsunami recorded in Japan.
On its western side it spreads from the Pacific Plate along the Juan de Fuca and Gorda ridges. It is a small remnant of the much larger Farallon Plate, most of which has already sunk beneath North America.
How fast it moves, and which way
At its center (45.4°N, 127.5°W) the Juan de Fuca Plate moves about 2.1 cm (0.8 in) a year toward the east-northeast. Because a plate turns around a pole rather than sliding in a straight line, the speed changes across it: from 1.5 cm (0.6 in) a year to 2.8 cm (1.1 in) a year, with an area-weighted average of 2.1 cm a year. That average makes it the 40th fastest of the 52 plates.
These figures are measured against the average motion of all the plates together (the “no-net-rotation” frame), which is how plate speeds are usually quoted. Measured against the North American Plate instead, the Juan de Fuca Plate moves about 4.0 cm (1.6 in) a year toward the east-northeast at its center.
In the model it rotates about a pole at 28.1°S, 58.3°E at 0.613° per million years. The speeds are averages over years to millions of years of measurement; earthquakes move the ground near a boundary in sudden steps instead.
Neighboring plates and boundaries
Its edges run for 3,310 km (2,060 mi): 43% convergent, where plates move together; 32% divergent, where they move apart; and 25% transform, where they slide past each other. It sinks beneath the North American Plate at subduction zones.
| Neighbor | Shared edge | Boundary types | Relative speed |
|---|---|---|---|
| Pacific Plate | 1,900 km (1,180 mi) | Divergent 57% · Transform 43% | 5.6 cm a yearup to 5.6 cm |
| North American Plate | 1,420 km (880 mi) | Convergent 100% | 4.0 cm a yearup to 4.8 cm |
Relative speed is how fast the two plates move against each other along their shared edge, averaged over its length.
Volcanoes on the Juan de Fuca Plate
The Smithsonian Global Volcanism Program lists 8 volcanoes on this plate that have been active in roughly the past 12,000 years. The most recent eruptions on record:
- Axial Seamount Seafloor, 2015
- North Gorda Ridge Segment United States, 1996
- Cleft Segment Seafloor, 1986
- Cobb Segment Canada, about 1,180 BCE
- Escanaba Segment United States, about 2,260 BCE
- Endeavour Segment Canada, about 3,490 BCE
Where the edges are blurred
Parts of this plate lie in the Gorda-California-Nevada zone, which the model marks as broad belts of deformation rather than sharp plate edges. There the motion between plates is spread over many faults, and a single boundary line is a simplification.
Sources
Outline, area, boundary types and motion: Bird, P. (2003), An updated digital model of plate boundaries, Geochemistry Geophysics Geosystems, 4(3), 1027, doi:10.1029/2001GC000252. Released by its author into the public domain (CC0 1.0). Areas are the model’s published figures; speeds, directions, boundary lengths and countries are calculated from its outlines, boundary steps and rotation poles.
Volcanoes: Global Volcanism Program, Smithsonian Institution, Volcanoes of the World (v. 5.4.0). Country outlines: Natural Earth.