Continent-Sized Blobs Beneath Africa and the Pacific Are Not Twins and May Be a Billion Years Old

Two continent-sized masses sit about 1,800 miles beneath Earth’s surface, perched on the molten outer core. One lies under Africa. The other sits under the Pacific. Seismologists first noticed them in the 1980s because earthquake waves slow by roughly 1 to 3 percent as they pass through — a sign the material is hotter, denser, or chemically different from the surrounding mantle. Researchers call them Large Low-Shear-Velocity Provinces, or LLSVPs. Each can tower the equivalent of 100 Mount Everests. Together they occupy a few percent of the planet’s volume and a much larger share of the deep interior. No drill can reach them. Everything known arrives as waves from big earthquakes and as supercomputer runs that try to match those waves to a picture of rock no one will ever hold.

A 2023 Nature paper led by Caltech’s Qian Yuan offered the most cinematic origin story: wreckage from Theia, a Mars-sized protoplanet that slammed into Earth about 4.5 billion years ago and flung debris that became the Moon. In that model, iron-rich Theia mantle sank and stayed, like wax at the bottom of a cooled lava lamp. If true, the blobs are the buried remainder of another world. The idea caught headlines because it tied two unsolved problems — the Moon’s birth and the two slow patches at the core-mantle boundary — into a single collision. It also left a testable claim: the piles should look like leftover planetary interiors, not like recycled ocean crust that has been diving into the mantle for hundreds of millions of years.

Recycled Seafloor, Not a Dead Planet — and Two Different Piles

Newer work has pushed back. On February 6, 2025, geodynamicist James Panton of Cardiff University and colleagues published in Scientific Reports models of mantle circulation over a billion years. They concluded the blobs can form from the ordinary recycling of ocean floor. When plates dive, cold oceanic crust sinks and piles up above the core. « They are evolving by themselves, » Panton told Live Science. The paper, « Unique composition and evolutionary histories of large low velocity provinces, » also killed the idea that the two masses are twins. The Pacific blob is younger and holds about 50 percent more recently subducted crust, refreshed for 300 million years by the Ring of Fire. The African blob is older, more mixed, and more buoyant, which is why it rises higher off the core. They look similar to seismic waves mainly because temperature, not chemistry, dominates wave speed. Oxford seismologist Paula Koelemeijer was a co-author.

A separate Nature study dated January 22, 2025, from Arwen Deuss’s group at Utrecht University measured not just wave speed but energy lost along the path. The waves barely weakened. That implies unusually large mineral grains, the kind that form when material sits still for enormous spans of time. « They must have been there for at least a billion years, » Deuss said. Utrecht’s public summary put a floor of half a billion years and allowed that the piles could be older still. « There is less flow in Earth’s mantle than is commonly thought, » the team argued. In November 2025, Yoshinori Miyazaki of Rutgers and colleagues floated a third option: that some material leaked from Earth’s core in the planet’s infancy and mixed into the mantle. « They are fingerprints of Earth’s earliest history, » Miyazaki said. A Nautilus review in April 2026 left the fight open: primordial leftover, alien planet, or seafloor graveyard.

Whatever they are, they are not inert. Scientists tie the piles to deep plumes that feed volcanic hotspots — Hawaii, Iceland, Réunion — and to some of the largest eruptions in the rock record, the kind associated with mass extinctions. Because they change how heat leaves the core, they may shape the magnetic field that shields the surface from solar wind. The African pile has been linked to continental uplift, the African superswell, river courses, and the landscapes where early humans evolved. Some researchers nickname the African mass Tuzo and the Pacific mass Jason, after scientists who pushed plume theory. The nicknames are informal. The structures are not. A hotspot that looks like a tourist volcano on a map can, in this view, be the surface expression of a pile that has been sitting on the core since before there were trees.

The method that keeps rewriting the story is almost stubbornly indirect. Seismologists wait for large earthquakes, then compare how long shear waves take to cross the lowermost mantle and how much energy they lose. Tomography turns those delays into maps. Geodynamic models then ask whether sinking slabs, a Theia remnant, or core leakage can reproduce the maps. Each camp can point to a paper that fits its favorite ingredient. None can send a probe. That is why a 2025 attenuation study that found giant grains, and a 2025 circulation model that found two different chemical histories, mattered more than another artist’s rendering of red blobs under a cutaway Earth. The maps got sharper. The origin story got messier, which is usually a sign the science is working.

Textbook language still treats the mantle as a slow conveyor that swallows seafloor on one side and coughs volcanoes on the other. The LLSVP debate says the conveyor has two warehouses at the bottom, they are not the same age, and they may have been storing heat and chemistry since before complex animals appeared. If Panton is right, the Pacific warehouse is still taking deliveries from the Ring of Fire. If Deuss is right, both warehouses have been sitting long enough for crystals to grow huge. If Yuan is right, some of the inventory arrived on a planet that no longer exists. Those sentences can all be partly true. The core does not care which journal wins the week.

Classroom globes still show a solid shell and a liquid core. They do not show two warehouses of slow, hot rock the size of continents parked on that core. Every few years a new paper claims to have identified the inventory. The 2025 work did something more useful. It showed the warehouses are different ages, different mixes, and old enough that any origin story has to survive a billion years of stirring that never quite stirs them away.

The AEGIS Alliance files deep-Earth puzzles with other first-look science, including a first-of-its-kind addiction study, reporting on plans for farms on Mars, and science and unexplained coverage of research that rewrites textbooks. For now the blobs remain what they were in the 1980s: two slow patches no one can visit, large enough to matter, still unnamed in any language but jargon. The 2025 papers did not close the origin debate. They made a simpler claim harder to dodge. The piles under Africa and the Pacific are not twins, they are old, and they are still moving heat toward the world that lives on top of them.