Researchers have identified two massive hot rock formations at the base of Earth's mantle that have influenced the planet's magnetic field for millions of years. Located about 2,900 kilometers beneath Africa and the Pacific Ocean, these structures create uneven heat at the core-mantle boundary. The discovery, based on ancient magnetic data and simulations, reveals variations in magnetic stability over vast timescales.
Deep within Earth, exploration remains limited; while humans have traveled 25 billion kilometers into space, drilling has only penetrated just over 12 kilometers into the planet's crust. This gap in knowledge is particularly acute at the core-mantle boundary, a critical interface now illuminated by new research.
A team led by the University of Liverpool, in collaboration with the University of Leeds, published findings in Nature Geoscience on February 5, 2026. Using palaeomagnetic records from rocks worldwide and supercomputer simulations of the geodynamo—the process generating Earth's magnetic field through liquid iron flows in the outer core—the scientists modeled magnetic behavior over the past 265 million years.
The study highlights two enormous, superheated rock bodies surrounded by cooler material, positioned pole-to-pole. These formations cause sharp thermal contrasts at the outer core's upper boundary, with hot zones leading to stagnant iron flow beneath them, contrasting with vigorous motion under cooler areas.
"These findings suggest that there are strong temperature contrasts in the rocky mantle just above the core and that, beneath the hotter regions, the liquid iron in the core may stagnate rather than participate in the vigorous flow seen beneath the cooler regions," said Andy Biggin, Professor of Geomagnetism at the University of Liverpool.
Some magnetic field elements have stayed stable for hundreds of millions of years, while others shifted dramatically. This challenges assumptions of a uniformly aligned ancient field, with implications for understanding Pangaea's formation, ancient climates, palaeobiology, and resource origins. The work stems from the DEEP research group, established in 2017 with funding from the Leverhulme Trust and the Natural Environment Research Council.