Evidence of past deformation found in Earth's lower mantle, shaping surface and interior New insights into Earth's evolution: Researchers discover ancient flow field in lower mantle . Credit: scitechdaily.com

Researchers from China and Japan have discovered unique characteristics in the flow patterns of the lower mantle. By studying seismic anisotropy in the lower section of the mantle beneath the Philippine Sea Plate, they have found evidence of an ancient flow field that still exists today. These findings were published in the journal Nature Geoscience.

The lower mantle is a crucial layer of the Earth that may hold key insights into the planet's evolution and material movement. It is believed to be not only the final destination for subducted slabs, but also the source of mantle plumes - two major processes that shape the Earth's surface and interior. However, our understanding of the flow patterns and dynamics of the lower mantle is still limited.

To address this, the researchers used P-wave azimuthal anisotropy tomography to map the 3D structure of the crust and mantle up to 1,600 km beneath the Philippine Sea Plate. Their results revealed the presence of north-south fast velocity directions at depths of 700-900 km below the plate. They also identified two isolated fast velocity anomalies with northwestern-southeastern directions at depths of 700-1,600 km.

Interestingly, the north-south fast velocity directions were found to be unrelated to subduction or mantle plumes. Instead, they are believed to be remnants of the Pacific lower mantle flow field from around 50 million years ago, based on previous simulations and seismological evidence. The two isolated fast velocity anomalies were also found to correspond with seismic scatterers detected in previous studies, indicating that they may be remnants of the subducted Izanagi slab.

According to lead author Prof. Fan Jianke from the Institute of Oceanology of the Chinese Academy of Sciences, the northwestern-southeastern fast velocity directions in the two isolated anomalies are believed to reflect the Pacific lower mantle flow field from around 40 million years ago. These observations provide important seismic evidence of past deformation in the lower mantle and can improve our understanding of its geodynamic properties.

Overall, this study highlights the widespread nature of seismic anisotropy in the lower mantle and provides valuable insights into the flow patterns and dynamics of this crucial layer of the Earth.

David Lamy
David Lamy Author
David Lamy owns the Bachelor in Atmospheric Science Degree. He is associated with Industry News USA from last 2 years. With proficiency in his work, David obtained a strong position at Industry News USA and heads the Science section. “Weather forecasting” is the field of his interest. He bags total 5 years of experience in this field. Apart from his routine work, David loves to explore his cooking skills. He has participated in various cookery shows.