We finally figured out why Earth still has a magnetic field, and it all comes down to exactly when our tectonic plates started moving.
March 27, 2026
Original Paper
Core and mantle thermal evolution constraints on the onset of plate tectonics and a long-lived geodynamo
arXiv · 2603.25232
The Takeaway
Scientists have faced a 'core paradox' where Earth's center should have cooled too quickly to sustain our protective magnetic shield. This study suggests that a delayed start to plate tectonics acted as a thermal regulator, slowing down the cooling just enough to keep the planet's 'engine' running for billions of years.
From the abstract
Earth's long-lived geodynamo is difficult to reconcile with recent high estimates of the core thermal conductivity, a problem known as the new core paradox. At the same time, the long-term thermal evolution of the mantle remains uncertain, largely due to the poorly constrained onset of modern-style plate tectonics, which marks the transition to efficient cooling of the interior through mobile-lid convection. Because core cooling -- and thus magnetic field generation -- depends on the efficiency