A recent study published in the journal Nature has revealed the existence of two colossal mountain-like structures hidden 1,200 miles beneath Earth’s surface, each estimated to be over 1,000 kilometers (620 miles) tall. These formations, identified as Large Low Shear Velocity Provinces (LLSVPs), are located under Africa and the Pacific Ocean—and they’re more than 100 times taller than Mount Everest.
The discovery, made through detailed seismic modeling using normal-mode oscillations, provides new insights into the planet’s deep interior and challenges long-held assumptions about how Earth’s mantle behaves.
Seismic Waves Uncover Giants Hidden in the Mantle
The study, led by Arwen Deuss and colleagues, used whole-Earth oscillations—a technique that tracks how the entire planet vibrates after large earthquakes—to map out the three-dimensional attenuation properties of the Earth’s mantle. These seismic waves travel at different speeds depending on the density, temperature, and composition of the materials they pass through.
In the regions below Africa and the Pacific, the team noticed significantly slower wave speeds, pointing to the presence of massive, anomalous structures at the core-mantle boundary. These are the LLSVPs—dense, thermochemically distinct domains that stretch across thousands of kilometers and tower higher than anything seen at Earth’s surface.
Not Mountains in the Traditional Sense—But Much Bigger
While they are referred to as “mountains” due to their immense vertical extent, LLSVPs aren’t made of solid rock formations like those on Earth’s crust. Instead, they are regions of chemically and thermally distinct mantle material. Their unique physical properties cause seismic waves to slow down, which is how researchers were able to detect them.
According to data cited in Nature, these zones measure roughly 1,000 kilometers high and span up to 5,000 kilometers wide—comparable in scale to entire continents. These aren’t just large; they are among the largest known structures inside the planet.
Possibly Billions of Years Old
One of the most compelling aspects of the discovery is the age and stability of the LLSVPs. The study suggests these structures may have formed from ancient tectonic plate material that sank into the mantle during subduction billions of years ago. This would make them some of the oldest stable structures on Earth, persisting since the early stages of the planet’s formation.
LLSVPs are often described as being located in “slab graveyards”—regions where cold, dense sections of the Earth’s crust descend toward the core. But unlike the surrounding mantle, which is believed to circulate and evolve over time, these provinces appear chemically distinct and thermally insulated, resisting disruption.
They’re Hot, Dense—And May Affect Surface Geology
These massive mantle structures are hotter than the surrounding mantle, adding complexity to the longstanding belief that colder regions dominate the lower mantle. The density and temperature variations between LLSVPs and their surroundings may help drive mantle plumes—the upwellings of hot rock that can lead to volcanic hotspots like Hawaii and Iceland.
There’s growing evidence that LLSVPs might also influence plate tectonics, including the location of supercontinent breakups. Some scientists suggest they may act as anchoring points for mantle convection currents, thereby influencing surface geology in ways we’re only beginning to understand.
A 3D Model That Changes How We Understand Earth’s Interior
The model presented in the Nature study is the first global 3D model of mantle attenuation derived from seismic normal modes. This means it doesn’t just map out where things are—it gives insight into how energy moves through them, helping researchers distinguish between temperature effects and compositional differences.
In particular, the model found that low attenuation—meaning less energy is lost as waves pass through—correlates with the same zones showing low seismic velocity. This alignment supports the idea that these LLSVPs are long-lived and compositionally distinct, not just thermal anomalies.
Everest Still Rules the Surface—But Not the Earth
While Mount Everest will likely remain the highest point above sea level for the foreseeable future, it’s now clear that Earth’s tallest structures aren’t above us—they’re beneath us. These massive, ancient mountains reshape how we understand the geological past, the structure of our planet, and even the forces shaping surface life today.
What’s more, researchers believe this is just the beginning. With improving seismic imaging technology, even more hidden structures may be discovered in the coming years