Scientists discover giant blobs deep inside Earth are ‘evolving by themselves’ — and we may finally know where they come from

Deep within Earth’s mantle, two massive regions known as “large low velocity provinces” (LLVPs) have long puzzled scientists. These blobs, located beneath the Pacific Ocean and Africa, are characterized by seismic waves that travel 1% to 3% slower than in the surrounding mantle. A new study suggests these LLVPs may have formed from ancient oceanic crust that was pushed into the mantle through subduction over the past billion years. 

Published on February 6 in the journal *Scientific Reports*, the research used computer modeling to trace the movement of subducted crust and determine whether it could create features similar to the LLVPs. The findings indicate that the recycling of oceanic crust through subduction—a process where one tectonic plate slides beneath another—can explain the existence of these blobs without requiring additional primordial material from Earth’s formation. 

James Panton, a geodynamicist at Cardiff University and lead author of the study, explained that the LLVPs beneath the Pacific and Africa likely formed independently through subduction. “They are evolving by themselves, simply through the process of subduction of oceanic crust,” Panton told *Live Science*. 

The study also revealed differences between the two LLVPs. The Pacific LLVP, fed by the active subduction zones of the Pacific Ring of Fire, is younger and denser due to a higher concentration of basalt, a volcanic rock. In contrast, the African LLVP is older, less dense, and more mixed with surrounding mantle material, extending about 342 miles (550 kilometers) higher in the mantle than its Pacific counterpart. 

While the research supports the idea that subducted crust is the primary source of the LLVPs, Panton noted that a thin layer of ancient material from Earth’s early days might still exist at the base of the mantle, potentially contributing to the blobs. 

The study also raises questions about the timing of subduction on Earth and its relationship to the formation of LLVPs. Subduction may have begun as early as 4 billion years ago or as recently as 1 billion years ago, and the LLVPs could have started forming shortly after subduction began. 

Future research will explore how mantle plumes—hot, upwelling regions of the mantle that fuel volcanic hotspots like Hawaii—interact with subduction processes and influence the LLVPs. 

This discovery sheds new light on the dynamic processes shaping Earth’s interior and highlights the complex interplay between tectonic activity and the planet’s deep structure.