Tuesday, 23 February 2021

Ancient kauri tree maps geomagnetic flip

The Earth’s magnetic field is fundamental to the existence of life. It deflects harmful solar winds and keeps our protective atmosphere in place. Every few hundred thousand years on average it completely flips, with magnetic north switching places with magnetic south. The last major geomagnetic reversal occurred 780k years ago. Geomagnetic excursions are short-lived, and involve temporary changes to the Earth’s magnetic field. The most recent recorded geomagnetic excursion is known as the Laschamps excursion and it took place around 42,000 years ago. The Laschamps Excursion was the last time the magnetic poles flipped. They swapped places for about 800 years before swapping back again. A kauri tree trunk was found perfectly preserved for 42,000 years, with its rings offering a 1,700-year record of the Laschamps Excursion.
Researchers compared the newly-created timescale with records from sites across the Pacific and used it in global climate modeling, finding that the growth of ice sheets and glaciers over North America and large shifts in major wind belts and tropical storm systems could be traced back to the Laschamps Excursion.
The study showed a depleted ozone layer, higher levels of ultraviolet radiation and increased atmospheric ionization that all coalesced about 42,000 years ago.