The reversal of the Earth’s magnetic field more than 40,000 years ago was responsible for several extinctions

Without the earth’s magnetic field, we will have a hard time living. Besides the simple fact that it helps us to navigate with a compass, it is fundamental to the existence of life. It effectively holds the earth’s protective shield in place and diverts the path of electrically charged particles that could hit our world.

However, this magnetic force is present both on Earth and in its crust, and its mantle is far from static. In reality it is dynamic. In particular, it changes position and fluctuates over time.

A petrified tree associated with the Laschamp event

The last complete reversal of the earth’s magnetic field goes back 42,000 years. This geomagnetic excursion, better known as the “Laschamp event”, therefore took place at the end of the last ice age. Although scientists have long been interested in this type of phenomenon, its real impact on life and the environment remains unclear.

An international team led by Chris Turney from the University of New South Wales in Australia then dealt with the subject. To do this, she analyzed a 42,000 year old tree fossil that had been discovered in New Zealand. “For the first time, we were able to accurately date the time of the last change in the magnetic pole and its effects on the environment,” said the expert.

A pole reversal

By analyzing the fossil of kauri, a tree native to New Zealand with a lifespan of more than 1,000 years, the researchers were able to determine the peak level of radiocarbon (carbon-14) in the atmosphere caused by the kauri’s toggling geomagnetic field.

The solar wind and the earth’s magnetic field. Image Credit: Shutterstock / VectorMine

The results show that the magnetic field not only reversed (the North Pole moved south), but also lost much of its strength over a period of several hundred years. 500 years ago, 42,000 years ago, the Earth’s magnetic field lost up to 6% of its strength (up to 28% of its current strength).

Painful consequences

The researchers’ conclusions regarding the consequences of the event are appalling. The study, published in the journal Science, cites the dramatic climate change leading up to the few hundred years in which the position of the poles changed.

The effects of the earth and living things of that time included a depletion of the ozone layer, an increase in atmospheric ionization, higher UV radiation, but also dangerous exposure to the solar wind. Disturbing phenomena that would have led to the extinction of the Neanderthals.

It remains to be seen when the next reversal will take place. Norbert Nowaczyk, researcher at the German Research Center for Geosciences in Potsdam and one of the authors of the study, notes that the earth’s field has been weakened for around 2000 years … One thing is certain, another collapse of the earth’s natural protective shield would be a major one Challenge for our generation, which is heavily dependent on electronics.