Strange zones affecting the magnetic field discovered in the Earth's interior

Scientists have discovered that mysterious ultralow-velocity zones (ULVZs), located at the boundary between Earth's core and mantle at a depth of about 2900 km, may play a key role in heat exchange within the planet and the functioning of the geodynamo - the mechanism that forms the magnetic field.

As reported by BAKU.WS, the work was published in the journal Nature Communications (NatCom).

ULVZs are relatively small areas (tens of kilometers in height and about a hundred kilometers in width), "stitched" to the base of the mantle. Seismologists have long known that seismic waves propagate noticeably slower in them, and the density of matter is higher than in surrounding rocks. However, their real influence on Earth's evolution remained unclear.

A team led by Wen-Ping Hsieh from the National Taiwan University directly measured for the first time the thermal conductivity of iron-rich magnesiowüstite - a mineral considered the main candidate for the composition of ULVZs. The experiments were conducted using diamond anvils under extreme pressures and temperatures.

It turned out that the thermal conductivity of this material is abnormally low - significantly lower than that of the surrounding mantle rocks. According to scientists' calculations, because of this, ULVZs behave like local "thermal insulation blankets," making it difficult for heat to flow away from the core.

"Such zones can significantly change the distribution of heat flow at the boundary between the core and mantle and even cause local thermal stratification in the upper part of the core," explained Wen-Ping Hsieh. According to him, this is directly related to the energy balance of the geodynamo and, consequently, to the evolution of Earth's magnetic field.

The authors emphasize that the study only partially lifts the veil over processes in the planet's deep interior. "We still know very little about how Earth's internal 'engine' works - and there is still much work ahead," noted the scientist.

The results help better understand how small-scale structures in the interior can affect global processes - from the thermal history of the planet to the stability of its magnetic shield.