Human beings could not record the last time reversal of the magnetic poles of Earth occurred. However now with the help of the flow of ancient lava, it is possible for the scientists to estimate the duration of this phenomenon.
A group of scientists used volcanic records for studying the last magnetic field reversal that occurred almost 780,000 years ago. They found that this reversal might have taken much longer duration than what was expected by scientists previously. The paper has been published in Science Advances journal.
In the last 2.5 million years, the magnetic field of Earth reversed dozens of times, when north turned to the south and vice versa. It is known to the scientists that the last reversal occurred in the time of Stone Age but they have fewer details about the duration of the reversal and when it might occur next.
Scientists relied on the lava flow sequences which erupted near to the last reversal for estimating its duration. With the help of this method, scientists estimated that it went on for 22000 years which is indeed quite longer than the past estimates of 1000 to 10000 years.
Bradley Singer, a geoscience professor at the University of Wisconsin-Madison and the study’s lead author said the last reversal was quite complex which started within the outer core of the Earth. When he was performing studies on a Chilean volcano in 1993, he stumbled on a sequence of the lava which had partially recorded the process of reversal. In an effort to date the lava, Singer observed weird magnetic field directions in the lava flow sequences. These are some of the rarest records and Singer is one of the few scientists to date them. So this incident led to his life-long career goal to understand and explain the timings of the reversals of the magnetic field.
Reversals occur when the iron molecules in the outer spinning core of the Earth start to move in the opposite direction as the surrounding iron molecules around them. With an increase in numbers, the magnetic field present in the core of the Earth is offset by the molecules. As a result, the magnetic field of our planet gets weaker. John Tarduno, a geophysics professor at the University of Rochester said that this kind of duration of the reversal would weaken the protection of Earth from solar radiations.
Additional effects might include genetic mutations or extinctions when the exposure to UV Sunrays increases. Increasing Sun particles entering Earth would disrupt communication systems, GPS and other satellite-based communication.
Reports of a magnetic field in direction of Canadian Arctic to Siberia has started discussions over if the next field reversal is imminent and what effect would it have on life. Singer said that there is very less evidence that the decrease in field strength or shifting in the north pole’s position would mean a reversal in polarity in the coming 2000 years. Volcanic records are the best type of records of a particular place and time.
Journal Reference: Science Advances journal