The magnetic field shape of the Earth is defined by two factors: the particles that come from the sun and the north and south magnetic poles.
Apart from making the compasses point north, the magnetic field that covers the Earth also protects our planet from toxic radiation coming from space. In other words, it protects life on Earth.
Despite what we would think, the Earth’s magnetic field is not constantly steady. It has been found that every several thousands of years, the magnetic field reversed, meaning that north points south and south points north. This also results in making the magnetic field less strong.
During the last 160 years, the Earth’s magnetic field has been becoming alarmingly weaker. This decrease is focused on a large area of the Southern Hemisphere, covering a region from Chile to Zimbabwe, called “the South Atlantic Anomaly”. The magnetic field there is so weak, that it is dangerous for astronomical satellites and other spacecrafts to orbit over this area, as they are exposed to strong radiation, which affects their electronics.
This decrease may indicate that the magnetic poles are possibly going to reverse themselves, resulting in influencing our navigation and electricity systems. Moreover, as larger amounts of radiation would enter the atmosphere, a rise in cancer rates would be expected. There is not thorough comprehension yet of the intensity of these changes, thus, scientists try to find clues, using even certain unexpected methods, such as archaeomagnetism, which explores archaeological records to find out information on the magnetic field of the past.
Limpopo River Valley is an area that has provided scientists with the first archaeomagnetic information concerning southern Africa for the period of 1000 and 1600 A.D. Near 1300 A.D., the magnetic field in this region appeared a fast decrease, similar to the contemporary. And afterwards, it started increasing, not that fast though. Therefore, this phenomenon seems to be repeated, raising the question of whether it may have happened more than those two times that are recorded.
During the last ten years, scientists have gained data on earthquakes’ seismic waves, which can provide information on the density of the Earth layers, based on the speed the waves travel. The core-mantle boundary beneath an area in southern Africa, which is known as the African Large Low Shear Velocity Province, is characterized by a quite slow seismic wave speed. What is interesting here is that its eastern edge neighbors with the reversed polarity region. The observation that the two areas are so close helped scientists suggest a model that connects the two phenomena. That is, the iron flow in the Earth core is affected by the peculiar African mantle, and therefore, a change occurs in the magnetic field behavior at the eastern edge of the seismic province, resulting in reversing the polarity.
The model suggests that reversing proceeds rapidly and dims at a slower rate. And in certain cases, such a region may gain an extent that could prevail over the magnetic field of the Southern Hemisphere and cause the poles to flip. However, there is still a lot of evidence to be found so that the suggested model is further developed.
So, is the present field going to reverse in the next thousand years, or keep becoming less and less intense? The question is still open.