Study reveals very low-velocity zones may be more common in Earth’s mantle than previously thought

New research suggests that peculiar zones in Earth’s mantle, where seismic waves slow down 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 as much as 50 percent. The latest findings indicate that these enigmatic features may exist across large swaths of the mantle, not just near volcanic hotspots like Hawaii.

Exploring ULVZs

ULVZs are found in the lower mantle near the core boundary. They were originally associated with volcanic hotspots, where molten rock rises from deep within the Earth. But a new study 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 travel of seismic waves and found patterns that point to these slowdown zones outside previously known locations.

Discovering new insights

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

Possible Sources and Implications

There are theories suggesting that ULVZs may be remnants of ancient meteor impacts or that they may be actively formed in the present. Thorne speculates that these zones may be the result of mid-ocean basalt, formed on seafloor spreading ridges, that melts and forms pockets as it is subducted into the mantle. These pockets may then be redistributed by tectonic activity, contributing to the widespread occurrence of ULVZs.

Exploring the future

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