Where it is and what it carries
The Juan Fernandez Plate, also called the Juan Fernandez Microplate, covers about 98,000 square kilometers, or 0.02% of Earth’s surface. It lies in the southeast Pacific Ocean, between about 31° and 35° south, along the East Pacific Rise. It sits near the triple junction where the Pacific Plate, the Nazca Plate and the Antarctic Plate meet.
It is made entirely of young oceanic crust under deep water and carries no islands. It is one of the smallest plates in the PB2002 model.
What happens at its edges
On its western side, the plate spreads away from the Pacific Plate along a 528 km boundary at about 13.5 cm/yr on average. This is part of the East Pacific Rise and one of the fastest spreading boundaries on Earth.
On its eastern side, the plate meets the Nazca Plate along a 551 km boundary. Part of it is spreading ridge, and part of it is compressional, where the rotating block pushes against the Nazca Plate. The average relative speed is about 5.3 cm/yr, but it varies widely along the boundary because the microplate rotates.
In the south, a short boundary of about 160 km with the Antarctic Plate is mostly spreading ridge, with an average relative speed of about 5.3 cm/yr.
Why geologists separate it
Ship surveys of seafloor depth and magnetic stripes revealed two spreading ridges here with a rotating block between them. That block moves independently of the three large plates around it, which is why plate models such as PB2002 list it separately. Like the Easter Plate to the north, it shows how unstable triple junctions on very fast ridges can break off small pieces of seafloor.
Because it is small and remote, its exact boundaries and rotation rate are less certain than those of large plates.
Earthquakes
The dataset lists four earthquakes of magnitude 6.5 or larger on the plate since 1900, all far out at sea. The largest was an M7.0 earthquake in 2014 on the southern East Pacific Rise, followed less than an hour later by an M6.6 event nearby. Others were an M6.9 in 1925 and an M6.7 in 2021. The plate has no named volcanoes in the dataset, though new oceanic crust forms constantly along its spreading ridges.