It has long been known that the Moon contributes to the effect of tides on Earth, but a new study suggests it could be the missing link in the generation of our planet’s magnetic field.


Earth’s magnetic field is produced by the geodynamo; the motion of liquid iron alloy in its outer core.

The classical model of how this occurs requires the Earth to have cooled by about 3,000°C over the past 4.3 billion years, from 6800°C to 3800°C.

But recent computer models and geochemical studies of the Earth do not support this theory, according to the study, meaning there must be a missing source of energy contributing to the maintenance of Earth’s magnetic field.

Researchers from the National Center for Scientific Research (CNRS) have suggested that the Moon could be this missing energy source.

Tidal effects caused by the Moon deform Earth’s mantle, and it is this effect that could be simulating the motion of liquid iron alloy making up the planet’s outer core.

This would generate and maintain Earth’s magnetic field.

3,700 billion watts of power in total is generated by gravity and rotation as Earth and the Moon move around the Sun, and over 1,000 billion watts is thought to be available to cause this motion of liquid in the outer core.

Including the Moon in this model solves the classical paradox, according to the researchers.

Further, the Moon’s role in maintaining the magnetic field could also be contributing to major volcanic events occurring on Earth.

Because neither Earth’s rotation around its axis nor the Moon’s orbit are entirely regular, the effect on Earth’s core is unstable, leading to fluctuations.


Perhaps this is what causes heat pulses in the outer core, leading over time to peaks in the melting of Earth’s mantle and the eruption of volcanoes on the surface.


Iain Todd, BBC Sky at Night Magazine
Iain ToddScience journalist

Iain Todd is BBC Sky at Night Magazine's Content Editor. He fell in love with the night sky when he caught his first glimpse of Orion, aged 10.