Scientists discover massive underground mountains 100x taller than Everest

Mount Everest has held the title of Earth's tallest mountain for as long as anyone can remember. But researchers working with seismic data have now identified two formations buried so far beneath the surface that they make Everest look like a foothill. These mountains, located 1,200 miles down at the boundary between Earth's mantle and core, stretch roughly 620 miles high—a hundred times the height of Everest's 5.5-mile summit.

The structures are called Large Low-Shear-Velocity Provinces, or LLSVPs, and they sit beneath Africa and the Pacific Ocean. Scientists have known something unusual was down there since the 1990s, when seismic waves from earthquakes began behaving strangely at certain depths, slowing down in ways that didn't match the surrounding rock. For decades, researchers could only guess at what was causing these anomalies. The mystery persisted until teams at Utrecht University developed a clearer method of imaging the deep Earth using seismic waves as a kind of X-ray.

When large earthquakes occur, the planet vibrates like a struck bell. As those vibrations travel through the Earth, they encounter different materials and structures. When seismic waves hit the LLSVPs, the planet's "ring" changes pitch—it sounds out of tune. By mapping these distortions across many earthquakes, scientists were able to construct a picture of these massive buried mountains and, more intriguingly, understand what they're made of.

What makes the LLSVPs remarkable is not just their size but their age and behavior. The mantle, Earth's thickest layer, normally flows like an extremely thick liquid over geological time, constantly churning and mixing. The LLSVPs, by contrast, appear to be almost completely stationary. They consist of mineral grains far larger than the fine-grained rock that typically sinks into the mantle through a process called subduction, where one tectonic plate slides beneath another. These enormous grains take an incomprehensible amount of time to form, suggesting the LLSVPs have been sitting at the base of the mantle for at least a billion years—possibly much longer, perhaps even since Earth's formation.

Dr. Arwen Deuss, the lead seismologist on the research team, explained that the sheer viscosity of these structures prevents them from moving. "They form huge mountains, with a height of almost 1,000 kilometers," she said. Sujania Talavera-Soza, also from Utrecht University, noted that the large mineral grains composing the LLSVPs mean they cannot participate in the normal convection that drives mantle flow. They are, in essence, ancient islands of rigid material locked in place while the mantle churns around them.

The discovery fundamentally changes how scientists think about Earth's interior. The mantle, it turns out, cannot be as thoroughly mixed as previously believed, and it does not flow as uniformly or quickly as models had suggested. These buried mountains are not merely geological curiosities—they represent a major revision to our understanding of planetary dynamics.

As for climbing them: that remains impossible. The LLSVPs are hotter than their surroundings and sit so deep within the Earth that no current technology could reach them. Everest will keep its crown as the world's highest climbable peak. But in the story of Earth itself, these silent, ancient mountains hold a far more profound place—unseen monuments to the planet's deep history, enduring unchanged through billions of years while continents drift and oceans form above them.