Earth’s magnetic field is older than planet’s core, study says

A still unsolved question in geophysics today – whether the Earth’s magnetic field formed with the planet or emerged later – is moving towards an answer with a new study led by the University of Oxford and MIT: He managed to recover a 3.7 billion year old record of the Earth’s magnetosphere.

This means that activation of this important life-preserving domain occurred at the same time as that recorded in stromatolites, the oldest fossils on the planet. These rocky structures, formed by successive layers of sediment, minerals and microorganisms, date back to 3.5 billion years ago, and some date back to 3.7 billion years ago.

The new study, published in the journal Advancing Earth and Space Sciences, suggests: An invisible shield already existed around the Earth at that time, and to this day this shield serves as a protective barrier against dangerous cosmic radiation from space.

Measuring the strength of the Earth’s magnetic field

To prove their hypothesis, the researchers had to travel to an area in southwestern Greenland known as the Isua Supracrustal Belt. The region consists of a craton, a region of the Earth’s crust. In addition to having some of the oldest examples of the Earth’s outer layer, it is geologically stable with little tectonic activity and erosion.

The focus of the research was on iron particles that work like tiny magnets, recording the direction of the magnetic field since the crystallization process fixes them in that position. Measurements showed a density of 15 microtesla; This result was evaluated by the researchers to be as strong as the current 30 microtesla.

By comparing the direction of the magnetic field to the orientation of rocks deformed by geological changes, the researchers were able to indirectly determine the age of the magnetosphere.

How important is it to reassess the Earth’s magnetic field?

The Earth’s magnetic field is constantly maintained through a process called geodynamics, in which the movement of molten iron in the outermost part of the Earth’s core produces electrical currents. This movement of molten material flowing at high speed, called convection, reproduces a common dynamo, resulting in the formation of this bubble that protects us.

Also read: Earth’s inner core mysteriously changes every 8.5 years

The results of the new study showed that the mechanism that drove Earth’s original dynamo was as effective as the inner core solidification process that is believed to have contributed to the densification of today’s magnetosphere.

Understanding the change in the intensity of the Earth’s magnetic field over all these years is important to determining when the planet’s inner solid core formed. This information is necessary to evaluate the rate of heat escape from the planet’s interior. It is important information in understanding the functioning of tectonic plates.

Follow the latest studies on the formation of our planet at TecMundo. If you want, take the opportunity to take a look at what it looks like, the definitive map of Earth’s tectonic plates.