An ancient Kauri tree, perfectly preserved for 42,000 years, has given scientists a rare glimpse into a period when Earth’s magnetic field went haywire. This 2021 study reveals a time of temporary environmental chaos that may have played a role in various aspects of life on Earth, ranging from an increase in cave paintings to the extinction of Neanderthals.
The Earth’s Dynamic Magnetic Field
Earth’s magnetic field is essential for the existence of life on the planet, as it deflects dangerous solar winds and maintains our atmosphere. However, it is not static; it constantly shifts and fluctuates. Full geomagnetic reversals, where magnetic north and south trade places — happen every few hundred thousand years. Shorter disruptions, known as geomagnetic excursions, also occur.
The Laschamps Excursion
The latest geomagnetic excursion is the Laschamps Excursion, which occurred approximately 42,000 years ago. During this event, the magnetic poles switched for 800 years before returning to their original positions. Although scientists have known about these events for a long time, the exact impact on life and the environment remains unclear.
Ancient Kauri Tree Discovery
Workers in New Zealand discovered a giant Kauri tree trunk preserved for 42,000 years. The tree’s rings provided a 1700-year record of the Earth’s environmental conditions spanning the Laschamps Excursion.
Precise Dating of the Magnetic Pole Switch
The ancient tree allowed scientists to accurately date the timing and environmental impacts of the last magnetic pole switch. The tree’s radiocarbon data helped to create a timeline of Earth’s atmosphere during the Laschamps Excursion.
The Adams Transitional Geomagnetic Event
This study revealed a period of dramatic environmental change, particularly in the time leading up to the magnetic field reversal. Researchers observed a depleted ozone layer, increased ultraviolet radiation, and increased ionization of the atmosphere around 42,000 years ago. This period has been named the “Adams Transitional Geomagnetic Event,” a tribute to the late Douglas Adams, who wrote “The Hitchhiker’s Guide to the Galaxy,” where the number 42 is the answer to the ultimate question of life, the universe, and everything.
Environmental Conditions During the Adams Event
During the Adams Event, auroras would have been widespread across the planet, accompanied by electrical storms due to increased ionized air. The strength of the magnetic field decreased to just 0–6%.
Cave Art and the Need for Shelter
According to the study, the disruption of the magnetic field led to an increase in cave art, as humans sought shelter from increased levels of ultraviolet rays. A common motif of cave art is red ochre handprints, which may have been used as sunscreen.
Possible Connections to Extinctions
The research speculates that the Adams Event could have been a contributing factor to the extinction of megafauna species in Australia as well as the decline of Neanderthals. However, these hypotheses remain controversial.
A Warning for Today
The study provides insights into how a similar event would affect the world today. Current movements of the north magnetic pole and the weakening of Earth’s magnetic field could be preconditions for an imminent reversal.
Consequences of a Modern Magnetic Field Disruption
If a similar event were to occur today, the consequences would be significant for modern society. Cosmic radiation could damage electric power grids and satellite networks.
Earth’s Deteriorating Magnetic Field
The Earth’s magnetic field has been weakening for at least 2,000 years. It was found to be nine percent weaker compared to direct measurements made 170 years ago, with thirty percent weakening in the area of the South Atlantic.
Unanswered Questions
Whether that weakening foreshadows that a pole reversal is forthcoming in the next one to two thousand years, is debatable. However, a collapse of the natural radiation shield would be a serious problem for our present-day society, which relies heavily on electronics.
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