Researchers discover potentially widespread zones in Earth’s mantle

New research suggests that strange zones in the Earth’s mantle where seismic waves slow dramatically may be more common than previously thought. These ultra-low-velocity zones (ULVZs) have intrigued scientists for years because of their ability to slow seismic waves by up to 50 percent. Recent findings indicate that these puzzling features may be present across large parts of the Earth’s mantle, not just near volcanic hotspots like Hawaii.

Exposing ULVZs

ULVZs are found in the lower mantle, near the boundary with the core. They were initially associated with volcanic hotspots, where molten rock rises from deep within the Earth. However, a new study led by geologist Michael Thorne, published in AGU Advances, suggests that these zones may be widespread. Thorne’s team used data from deep earthquakes to model the movement of seismic waves and discovered patterns that suggest these slowing zones exist outside previously known locations.

Revealing new insights

The research focused on waves from powerful earthquakes, which travel through different layers of the Earth, including the core and the mantle. Precursor PKP waves, which arrive before the main seismic waves, were found to propagate through unknown features in the mantle. This led to the discovery of potential ULVZs not only under specific regions such as the western Pacific Ocean, but also in areas such as North America, North Africa and Papua New Guinea.

Possible origins and implications

There are theories that ULVZs are the remnants of ancient meteorite impacts or that they may be actively forming today. Thorne speculates that these zones may be the result of mid-ocean basalt, formed at seafloor spreading ridges, melting and creating pockets as it is subducted into the mantle. These pockets can then be redistributed by tectonic activity, contributing to the widespread nature of ULVZs.

Future exploration

Understanding ULVZs could expand our understanding of volcanic hotspots and mantle dynamics. Despite the progress, many questions remain unanswered. As researchers continue to investigate these mysterious features, they hope to learn more about the processes that shape our planet’s interior.