The Philippine Sea plate is Earth's most well-traveled tectonic record of the Cenozoic era

Nature · Published 3 October 2026 Swipe more like this →

In short: As one of the largest marginal sea plates in Southeast Asia, the Philippine Sea plate has migrated over 2,000 kilometers northward from equatorial latitudes. This massive journey across the western Pacific makes it a unique, mobile laboratory for geologists studying the hidden boundaries of Earth's deep mantle domains.

The Philippine Sea plate (PSP) is a complex mosaic of oceanic basins and island arc lithosphere, with a history stretching from the Cretaceous period to the present day. Because it has traveled so far during the Cenozoic, it provides an unparalleled spatiotemporal record of tectonic activity. While the precise details of its history remain a subject of scientific debate, the plate's movement has allowed it to traverse the boundary between two massive, distinct mantle domains: the Indian and Pacific mantle domains.

Geochemists identify these domains by the isotopic signatures of basalts found on the ocean floor. The Indian-type mantle is characterized by higher levels of lead and strontium isotopes compared to the Pacific-type mantle. By analyzing lava samples from ancient features like the Gagua Ridge—which dates back to approximately 123–124 million years ago—researchers can track how the plate moved across these geochemical borders. This movement helps clarify the long-term stability and location of these global-scale mantle heterogeneities, which are thought to have existed since at least the Cretaceous or even the Permian.

The plate's internal structure is equally dynamic, containing active spreading centers like the Mariana and Ayu Troughs. Older basins, such as the Shikoku and Parece Vela, formed between 30 and 15 million years ago, while the West Philippine Basin began spreading in the early Cenozoic, roughly 52 to 58 million years ago. This spreading was likely initiated by a mantle plume, a process that may still be active today under the Manus Basin. By synthesizing this magmatic history, scientists are now uncovering evidence of a third, distinct Zealandia-Antarctic mantle domain, which appears to be three times larger than previously estimated.

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