Where it is and what it carries
The Philippine Sea Plate covers about 5.4 million square kilometers, or 1.07% of Earth’s surface. Most of it is ocean floor beneath the Philippine Sea, divided into the West Philippine Basin, the Shikoku Basin and the Parece Vela Basin. On land it carries all of Palau, 70.8% of Taiwan, 18.7% of the Philippines, 22.8% of the Federated States of Micronesia and Japan’s Izu and Bonin islands.
The plate is unusual because nearly all of its edges are subduction zones or collision zones. It has no large mid-ocean ridge shared with a major plate. Its seafloor was built instead by back-arc spreading behind volcanic arcs.
Subduction on almost every side
On the west, the plate sinks beneath the Sunda Plate along 2,882 km, mainly at the Philippine Trench, at about 9.2-10.8 cm/yr. Farther north it dives beneath the Okinawa Plate at the Ryukyu Trench along 1,593 km, at about 5.8-13.5 cm/yr. At Taiwan it collides with the Yangtze Plate along 439 km at about 8.1-8.6 cm/yr, building the island’s mountains.
In the north, it subducts beneath southwest Japan on the Amur Plate at the Nankai Trough, 762 km long, at about 4.4-5.6 cm/yr. Near Tokyo, a 312 km boundary with the Okhotsk Plate includes the Sagami Trough and moves at about 3.4-3.6 cm/yr. At the far south, it subducts beneath the Bird’s Head Plate near New Guinea at about 1.5-2.2 cm/yr.
The east side is different. Here the Pacific Plate sinks beneath the Philippine Sea Plate at the Izu-Bonin Trench along 1,819 km, at about 1.8-6.1 cm/yr. Farther south, the plate is separated from the Mariana Plate by the Mariana Trough, a back-arc basin spreading at about 0.9-5.6 cm/yr. In the southeast, a 1,403 km boundary with the Caroline Plate near Palau moves very slowly, at under 1 cm/yr.
How it formed
The Philippine Sea Plate grew in pieces. The West Philippine Basin opened first. Later, as the Pacific Plate subducted beneath the eastern edge, the Izu-Bonin-Mariana volcanic arc split apart lengthwise, and the Shikoku and Parece Vela basins opened between the two halves. The same process continues today in the Mariana Trough. Over time, the whole plate has moved north and rotated clockwise, carrying its arcs toward Japan and Taiwan.
Earthquakes and volcanoes
The dataset lists 193 earthquakes of magnitude 6.5 or larger on the plate since 1900, one of them magnitude 8 or more: the 1920 Hualien earthquake in eastern Taiwan (M8.2). The 1999 Chi-Chi earthquake (M7.7, centered near Puli) also falls on the plate in PB2002 and was one of the deadliest in Taiwan’s history. In 2015 an M7.8 earthquake struck 664 km beneath the Bonin Islands, one of the deepest large earthquakes ever recorded, inside the Pacific slab sinking under the plate.
The plate holds 31 volcanoes in the dataset, most of them along the Izu-Bonin arc. Izu-Oshima and Miyakejima erupt every few decades, and Miyakejima’s 2000 eruption forced the evacuation of the whole island. Farther south, Nishinoshima has grown into a much larger island through eruptions since 2013, and the submarine volcano Fukutoku-Oka-no-Ba released large pumice rafts in 2021. Ioto (Iwo Jima) is a caldera whose ground has been rising for decades.