In an African lake the history of the Earth's magnetic field

150,000 years of variations in the Earth's magnetic field have been reconstructed thanks to the analysis of sediments from Lake Chala , located near Kilimanjaro on the border between Kenya and Tanzania. These data, which provide valuable information on the history of the Earth and represent a point of reference for other geological and climatic studies in Africa, are published in the journal 'Geochemistry, Geophysics, Geosystems' by Lancaster University in the United Kingdom together with the National Institute of Geophysics and Volcanology and the University of Ghent in Belgium.

“Thanks to this study, we have obtained a detailed picture of the variations of the magnetic field in an area crucial for the history of human evolution,” explains Anita Di Chiara, researcher at the INGV. “Eastern Africa is considered one of the areas from which hominids moved away to populate the rest of the world, perhaps precisely because of extreme climate events”.

Lake Chala was the subject of a drilling project within the framework of the international I CDP DeepCHALLA program. By analyzing the 129 meters of sediments extracted , researchers were able to reconstruct the history of the Earth's magnetic field in the region. The dating was carried out with advanced geochronological methods, including radiocarbon and argon isotope ratios . The results highlight six magnetic excursions , or periods in which the magnetic field underwent significant variations. Among these, the most recent are the Laschamp (42,000 years ago), the Mono Lake (24,000 years ago) and the Hilina Pali (about 19,000 years ago) .

The precision of the data obtained has allowed us to redefine the age of the Hilina Pali excursion between 19,000 and 21,000 years ago, improving our knowledge of the frequency and duration of magnetic field instabilities. “The results of this research not only improve our understanding of the evolution of the Earth’s magnetic field, but also provide a methodological basis for future studies in other equatorial regions and the southern hemisphere,” adds Anita Di Chiara. “It is a significant step forward towards a more complete mapping of the magnetic history of our planet.”