Seismic analysis reveals ancient traces of mantle flow beneath the Pacific's oldest plate

Seismic analysis has uncovered ancient traces of mantle flow beneath the oldest preserved piece of Pacific Ocean crust. The patterns of this ancient flow, detected in the uppermost mantle, reveal a complex interplay of tectonic plate motion changes, mantle deformation around sunken lithosphere remnants, and hotspots. This study, published in Seismological Research Letters, provides a rare glimpse into past mantle flow beneath ancient oceanic plates and sheds light on how mantle flow drives plate tectonics and shapes Earth's crust.

The research team, led by YoungHee Kim of Seoul National University, studied seismic anisotropy to identify these traces of past mantle movement. They discovered that the anisotropy beneath the Pacific Triangle, located about 1,000 kilometers east of the Mariana Trench, is spatially variable and cannot be explained by plate motion alone.

The complexity of these patterns suggests a combination of inherited deformation and present-day mantle flow, possibly influenced by the region's long history of plate motion changes and hotspot interactions. The findings also reveal anomalies in the mantle below the Pacific Plate, including localized hotspot upwelling in some areas.

These results offer valuable insights into how local mantle structure may influence deformation and contribute to a more comprehensive understanding of mantle dynamics beneath the oldest Pacific seafloor.