Scientists say that 565 million years ago, the Earth’s magnetic field almost disappeared. But a geological phenomenon could save him. Most likely, at that time the liquid core of the planet began to harden, which strengthened the field. This is an important study, because the magnetic field protects the Earth and its inhabitants from harmful solar radiation - streams of plasma particles emitted by the sun.
Researchers have managed to rewind time and look at what the earth's core looked like in the past. To do this, we studied the crystals the size of a grain of sand. The team selected samples of plagioclase and clinopyroxene - minerals created 565 million years ago (found in eastern Quebec, Canada). These samples contain tiny magnetic needles with a size of 50-100 nanometers. Interestingly, in molten rock they were oriented in the direction of the magnetic field.
In fact, they are ideal magnetic recorders. When cooled, they fix a record of the earth's magnetic field, which is maintained for billions of years. By inserting crystals into the magnetometer, the researchers realized that the charge of the particles was extremely low. To be more precise, 565 million years ago the Earth’s magnetic field was 10 times weaker than current indicators (the weakest recorded one).
It also turned out that the inversion frequency of the north and south poles was very high. So, the field behaved extremely strange. It was a critical point when the earth dynamo almost collapsed! But then there was a second push from the very core of the planet. In the first years of the Earth’s existence, the core was in a liquid state. But at the time between 2.5 billion and 500 million years ago, iron began to cool and freeze in the center of the planet. As the inner core solidified, lighter elements, such as silicon, magnesium, and oxygen, were pushed into the outer liquid core layer, leading to fluid movement and heat (convection). This movement supported the mobility of charged particles, which created an electric current, and behind it a magnetic field.
Convection continues to control and maintain the magnetic field today. The inner core of the earth is becoming stronger and will continue to develop over billions of years. Scientists blame weak geodynamics, which hints at the liquid state of the core. If the theory is correct, then the inner core was formed in time to recharge geodynamics and save our magnetic shield.
Soon after that, a Cambrian explosion occurred, and the planet was populated by complex organisms. Perhaps a weaker magnetic field has something to do with these evolutionary events, as it could transmit more radiation, which damages DNA and causes mutations. That is, the number and variety of species has increased.
So far, these are just assumptions and guesses, because it was not possible to obtain evidence of mutations for a fixed weakening of our magnetic field (for example, when rebuilding the north and south poles).