A clear cycle was found near the Earth's magnetic field
Scientists from the University of Liverpool studied the history of the Earth's magnetic field and came to the conclusion that its strength periodically decreases and then rises again. The cycles are 200 million years long, according to the Proceedings of the National Academy of Sciences.
The authors of the study performed paleomagnetic analysis of rocks from ancient lava flows in East Scotland. The samples were between 200 and 500 million years old.
The results showed that 332-416 million years ago, the strength of the geomagnetic field was less than 25% of what it is today. A similar decline also occurred 120 million years ago. The researchers called this period the Middle Paleozoic dipole minimum. Scientists have concluded that the strength of the Earth's magnetic field is cyclical and weakens every 200 million years.
The scientists noted that after the weakening they identified, the magnetic field came to stability and kept it for 50 million years. This phenomenon is called Kiman's Super Chron.
The Earth's magnetic field protects the planet from solar radiation. Scientists have long established that it is unstable. The north and south poles are constantly shifting and may even swap places completely. Knowledge of past changes in a field can indicate how it will behave in the future.
Weakening of the field has a direct impact on life on the planet. Recently, experts have found that the Devonian-Carboniferous mass extinction is associated with increased levels of UVB rays; at the same time, the strength of the magnetic field has noticeably decreased.
Earlier it became known that migrating animals, birds and even fish are able to navigate the Earth's magnetic field. So, the shark uses it as a GPS.