Recent studies reveal that two massive, enigmatic rock formations beneath Africa and the Pacific Ocean may play a crucial role in generating Earth’s magnetic field. These formations could have contributed to the field’s destabilization over millions of years.

Scientists have long been aware of these continent-sized rock blocks, which stretch nearly 1000 kilometers from the outer core to the upper mantle. They exhibit unique properties that slow seismic wave passage, although their depth complicates measurements, making precise differentiation challenging.

Andrew Biggin, a researcher from the University of Liverpool, explored Earth’s magnetic field for insights. This protective magnetic field, created over billions of years by molten iron convection in the core, extends thousands of kilometers into space, shielding our planet from solar winds and cosmic radiation.

The magnetic field’s shape is influenced by the heat energy transfer from the hot core to cooler zones. Biggin and his team theorized that analyzing changes in the magnetic field could unveil details about heat movement within the Earth’s core.

To trace the evolution of the magnetic field, researchers compared ancient volcanic rock records that captured magnetic orientations over millions of years. They simulated the heat flow in the core with and without the influence of large hot rock masses, correlating results with actual magnetic measurements.

Findings indicated that simulations incorporating these rock blocks aligned most closely with ancient magnetic data. “These convection simulations can reproduce notable features of the core’s magnetic field only when considering significant variability in heat flow at the core’s upper layer,” says Biggin.

This implies that these hot regions have likely maintained higher temperatures than their surroundings for millions of years, leading to diminished heat exchange between the core and mantle. Such discrepancies in heat flow may have significantly contributed to the creation and stabilization of the Earth’s magnetic field.

While many geologists view the Earth’s magnetic field evolution as symmetrical over time, Biggin’s research revealed inherent asymmetries in ancient fields, likely instigated by these rock formations. This discovery could refine how geologists interpret the movement of ancient rocks and reveal changes in Earth’s deep structure over time, according to Biggin.

If accurate, these temperature contrasts in the rock formations could also exist in the upper outer core, potentially detected through seismic wave analysis.

However, Sanne Kottar from Cambridge University expresses skepticism. “Mapping core variations is extremely challenging due to the vast mantle material we must analyze before accessing the core,” she explains.