A Hitchhikerâs Guide to an Ancient Geomagnetic Disruption A shift in Earthâs poles 42,000 years ago may have drastically altered the planetâs climate, scientists have found â and theyâre naming the period after the author Douglas Adams. An ancient kauri tree, unearthed near Ngawha Springs in New Zealand, bore witness to a lengthy disintegration of the planet’s magnetic field, a period known as the Laschamp excursion.Credit...Nelson Parker By Alanna Mitchell Feb. 18, 2021 About 42,000 years ago, Earth was beset with oddness. Its magnetic field collapsed. Ice sheets surged across North America, Australasia and the Andes. Wind belts shifted across the Pacific and Southern Oceans. Prolonged drought hit Australia; that continentâs biggest mammals went extinct. Humans took to caves to make ochre-color art. Neanderthals died off for good.