The most recent polar reversal, called the Laschamp excursion, happened about 41,000 to 42,000 years ago. During this time, the north magnetic pole moved to the southern hemisphere and then back to the north.
Scientists studied ancient kauri trees found in wetlands in northern New Zealand. These trees were alive during the Laschamp excursion. By analyzing the growth rings, researchers measured a spike in atmospheric radiocarbon levels, which occurred when Earth’s magnetic field weakened.
This helped them create a detailed timeline of the changes.
Earlier studies focused on what happened while the magnetic poles were reversed, during which Earth’s magnetic field was only 28% as strong as it is now. However, this new research revealed that the biggest changes happened during a transition period called the Adams Event. During this time, the magnetic field dropped to just 0-6% of its current strength.
Researchers compared their findings with data from other Pacific sites and used climate models to show how the Adams Event caused major environmental changes. These included the growth of ice sheets in North America and shifts in wind patterns and tropical storm systems.
Professor Anthony Dosseto from the University of Wollongong explained that the Adams Event caused dramatic changes to the planet’s climate. In Australia, for example, it became much drier. This event might explain the extinction of megafauna in Australia and the disappearance of Neanderthals in Europe.
The event may also explain the sudden rise in cave art during this time. As cosmic radiation increased, people likely sought shelter in caves, leading to a surge in cave painting.
The study warns that if a similar magnetic field shift happened today, the effects would be devastating. Cosmic radiation could destroy power grids and satellite systems while triggering rapid climate change.
Professor Dosseto stressed the importance of understanding this event: “What happened 42,000 years ago is terrifying and could happen again. The weakening of the magnetic field only lasted a few hundred years, but its effects on the climate, environment, and life lasted thousands of years. It’s a warning for our planet today.”
CCTO
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