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Researchers from the Universities of Leeds and Liverpool have uncovered surprising evidence of colossal, ultra‑hot rock formations hidden nearly 2,900 kilometers beneath our feet — structures that may have shaped Earth’s magnetic field for hundreds of millions of years.
A Dynamic World Beneath the Crust
Although humanity has ventured more than 25 billion kilometers into space, our understanding of Earth’s interior remains remarkably limited. The deepest man‑made borehole, drilled on Russia’s Kola Peninsula, reaches just 12 kilometers — barely scratching the planet’s thin crust, which ranges from 5 to 70 kilometers in thickness.
Below the crust lies the mantle, extending to a depth of about 2,900 kilometers. Beneath it sits the outer core, a churning ocean of molten iron whose movement generates Earth’s magnetic field. At the very center is the solid inner core, composed mainly of iron and nickel and held firm by immense pressure despite temperatures reaching around 5,700 degrees Celsius.
Hot “Blobs” the Size of Continents
In a new study published in Nature Geoscience, the British research team reports magnetic evidence of two enormous, unusually hot rock structures resting at the base of the mantle — one beneath Africa, the other beneath the Pacific Ocean.
These formations, described as “hot blobs,” appear to be made of solid, overheated material surrounded by a ring of cooler rock stretching from pole to pole. According to the simulations, these structures have long influenced the flow of molten iron in the outer core, thereby shaping Earth’s magnetic field over geological timescales.
A Magnetic Field with a Long Memory
To investigate the deep interior, the scientists combined paleomagnetic data — ancient traces of Earth’s magnetic field preserved in rocks — with advanced supercomputer simulations of the geodynamo.
Their results challenge long‑held assumptions. The temperature at the top of the outer core, once thought to be relatively uniform, instead shows dramatic thermal contrasts. Hot regions lie directly beneath the massive mantle structures, while cooler areas sit above more active flows of molten iron.
These variations appear to have left a lasting imprint on the magnetic field. Some parts of the field have remained stable for hundreds of millions of years, while others have shifted significantly.
“These results suggest strong temperature differences in the rocky mantle directly above the core,” said Andy Biggin, professor of geomagnetism at the University of Liverpool. “Under the hotter regions, the liquid iron tends to stagnate rather than join the vigorous flow beneath cooler areas.”
Implications for Earth’s History
The findings could reshape scientific understanding of how supercontinents like Pangaea formed and broke apart. They may also help resolve long‑standing uncertainties in paleoclimate research, evolutionary biology, and the formation of natural resources.
“For decades, it was assumed that Earth’s long‑term magnetic field behaved like a perfect bar magnet aligned with the planet’s rotation axis,” Biggin explained. “Our results suggest that this may not be entirely accurate.”
A Planet Still Full of Mysteries
The study follows a recent French investigation that detected a massive, unexplained shift deep within the Earth around 2007 — a phenomenon known as a “geomagnetic jerk.” The event, observed off the coast of Africa, likely originated near the core‑mantle boundary, though its cause remains unknown.
As scientists continue to probe the inaccessible depths of our planet, each discovery reveals just how dynamic — and mysterious — Earth’s interior truly is.
- source: heute.at/picture: pixabay.com
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