A New Map of Earth’s Core Suggests Something Strange Is Happening

Paul Earle, a graduate student, spent two weeks in a room full of boxes filled with nine-track computer tapes in the basement of the Albuquerque Seismological Laboratory during the 1990s. The labels were mysterious. The magnetic information on many of the tapes had been worn away by degradation. He was specifically searching for the seismic echoes of Soviet nuclear explosions that occurred on the Russian Novaya Zemlya islands in the early 1970s, captured by a variety of mechanical sensors buried 4,000 miles away in the Montana wilderness. The waves from those explosions had penetrated so far into the Earth that, before returning, they bounced off the solid iron ball at its center. Earle was attempting to interpret what they had witnessed.

The speed at which Earth’s inner core rotates in relation to the rest of the planet is a property that is so difficult to measure that estimates vary by an order of magnitude. Three decades later, the debate is still genuinely unresolved thanks to the data that eventually assisted a seismologist at the University of Southern California. However, since those tapes were first decoded, the story of what’s happening deep within our planet has become much more complex in ways that no one could have predicted.

A fifty-year mystery regarding the D” layer—a peculiar region about 2,700 kilometers below the surface where seismic waves mysteriously speed up—was resolved in June 2025 by research published by geoscientists at ETH Zurich. Motohiko Murakami of ETH referred to the explanation as “the last piece of the puzzle,” and it turned out to be horizontal flow. At that depth, tiny crystals of a mineral known as post-perovskite align in a single direction as solid rock, which is neither liquid nor brittle but something in between, moves slowly and steadily. Waves move differently when crystals line up. The acceleration ceased to be enigmatic. It turned into proof of a massive, unseen current that, up until now, no one had been able to establish existed in the deep interior of the Earth.

There seem to be two buildings in the same area that don’t resemble anything anyone would anticipate. Two continent-sized piles of unusually hot rock are located beneath Africa and the Pacific Ocean, at the base of the mantle where rock meets the liquid iron of the outer core. Although geophysicists have been aware of them for years, their significance has not yet been fully grasped. According to a 2026 study headed by Andy Biggin of the University of Liverpool, these “blobs”—Biggin’s term, apparently—may have been serving as a sort of thermal blanket for hundreds of millions of years, limiting the rate at which heat escapes the core beneath them.

This, in turn, affects the churning flows of liquid iron that produce Earth’s magnetic field. The simulations that treated these blobs as uneven insulators—hotter underneath and colder at their edges—were the ones that most accurately replicated the patterns found in ancient rock samples. The textbook assumption that Earth’s time-averaged magnetic field behaves like a perfect bar magnet aligned with the spin axis is called into question, according to Biggin. Instead, it bears a faint trace of the buildings that are hidden thousands of kilometers below.

The connections between all of this and the magnetic field are still being mapped. The field is the unseen force that has sustained life on Earth for billions of years, shields satellites and power grids from radiation, and prevents solar wind from removing the atmosphere. It is produced by the motion of liquid iron in the outer core, which is shaped by events at the boundary between the core and the mantle, where these blobs are located and where horizontal flow was discovered by the ETH researchers. The South Atlantic Anomaly, a growing weak spot in the field that grew by almost half the area of continental Europe between 2014 and 2025, has been monitored by ESA scientists. “Something special” is taking place in the field, according to Chris Finlay, who oversees the Swarm satellite analysis at the Technical University of Denmark. He takes care to clarify that even in areas where the magnetic shield weakens, the atmosphere offers sufficient insulation, so there is no immediate threat to life on the surface. However, it’s a genuine shift, and comprehending it necessitates comprehending the underlying causes.

There are still unanswered questions about the solid iron inner core at the heart of it all. According to a study published in Nature in February 2025, the inner core may have deformed, with its edges shifting by at least 100 meters, indicating that it changed shape in ways that only solid but somewhat plastic material can. According to other studies, it is growing more quickly on one side than the other, resulting in an uneven structure that asymmetrically accumulates iron. According to a paper published in December 2025, the inner core may be in a “superionic state” in which lighter atoms like carbon flow through the gaps while iron atoms form a solid lattice. The variety of descriptions is remarkable: mushy, lopsided, superionic, potentially altering its direction or rate of rotation. Paul Richards of Columbia University stated, “Something is changing down there,” with the measured accuracy of someone who has spent decades observing this field.

The fact that nearly all of this knowledge is indirect is difficult to ignore. The planet’s solid inner core starts 5,000 kilometers below the surface, and humans have only drilled about 12 kilometers into the crust. The behavior of waves—such as those from earthquakes, nuclear explosions, and waves that are scattered, bounced, and compared to their own echoes—is the source of all knowledge about what lies beneath. The maps being created are inferences rather than actual images, and the fact that these inferences consistently reveal unexpected details like flowing solid rock, hidden blobs, rotating iron, and weakening fields indicates that either the instruments are improving or the narrative was more intricate than the models predicted. Most likely both.

The interior of the Earth is not fully understood. One corroded Soviet tape at a time, one decade of satellite measurements at a time, one earthquake wave at a time, this landscape is being investigated. According to the most recent research, the layers beneath us are neither static nor simple; rather, they are changing, interacting, and moving in ways that have significant long-term effects on the planet’s magnetic health. It’s another matter entirely whether any of it matters in a human-scale timeframe. It’s being worked on by science.