Russian scientists have discovered that solidified magma can store information about Earth's magnetic field for billions of years. A study of over 40 ancient magmatic bodies in the north of the Siberian Platform made it possible to reconstruct the characteristics of the field that existed about 1.5 billion years ago. This was stated by Alexander Pasenko, a senior researcher at the Institute of Earth Physics of the Russian Academy of Sciences.
The secret lies in the magnetic minerals contained in rocks. As molten magma cools, they acquire magnetization related to the direction and strength of the magnetic field of that time. After solidification, the rock can retain this information for billions of years, allowing researchers to literally look into the planet's distant past.
Cooling magma acts like a natural tape recorder: as it solidifies, it 'remembers' the direction and strength of the magnetic field of its time.
By studying ancient magmatic formations in Siberia, specialists were able to determine the geographical latitude at which the Siberian Platform was located 1.5 billion years ago. This is especially important, since over such a long period, the position of parts of the Earth's crust has changed significantly due to the movement of tectonic plates.
The data obtained also helps to study the evolution of the Earth's core and the geodynamo — the mechanism by which the magnetic field is formed inside the planet. Analysis of the magnetization preserved in the rocks allows scientists to better understand how this mechanism worked in deep antiquity, long before the advent of modern observation methods.