150,000 years of history of the Earth's magnetic field reveals climate climate when the first humans spread from Africa
An African lake with trees rings has given a record for the magnetic field of the earth covering the last 150,000 years.
A nucleus of rock and sediments drilled from the bottom of Lake Chala, a picturesque crater lake on the border of Tanzania and Kenya, contains recordings of oscillations in the magnetic field of the planet. This rock also contains precious climate information in the past 150,000 years, when modern humans ran from Africa, in the Arabic and Europe and Asia peninsula.
“There is an effort to try to understand which conditions have led [humans] Leave Africa and populate the rest of the Eurasia, “said Anita di ChiaraPaleomagnetist at the National Institute of Geophysics and Volcanology of Italy in Rome. To use the old sediment records to rebuild the past climate, “we need ages,” said Di Chiara to Live Science. “We need a way to go out with these sediments.”
This is where the variations in the magnetic field of the earth come into play. Most of these rock records come from the posts, where these signals are stronger, said Di Chiara. “Getting an equatorial file is a bit special,” she said.
Scientists like Di Chiara can compare magnetic changes in rock strata of a single place, like Lake Chala, to diapers around the world where researchers already know how old are rocks. They can also use layers in the rock from events known to calibrate the data. For example, the core of Lake Chala includes a layer of ash from the Toba Supervolcanowhich broke out in Indonesia 74,000 years ago.
Lake Chala is a special place to get this type of data, said Di Chiara. It is a crater nourished by the runoff of the cliffs and surrounding forests, no large streams or rivers. This means that layers at the bottom of the lake are not mixed by occasional events, such as floods. Instead, the diapers are carefully stacked in season.
The researchers found six magnetic excursions – temporary fluctuations, sometimes located in the magnetic field – in the 150,000 -year record, they reported in April in the journal Geochemistry, geophysics, geosystems. One was an anomaly not seen elsewhere in the rock record, said Di Chiara. Such excursions can be caused by chaotic circulation in the internal nucleus of the earth or by interactions between the solid internal nucleus and the liquid external nucleus.
A magnetic excursion would probably have gone unnoticed to ancient Africans in the East, but today, fluctuations in the magnetic field are very much. Indeed, the magnetic field protects the planet from the solar wind, a flow of particles loaded with the sun. A lower field means more disruption of communications and electronic equipment of these particles.
Historical data will help researchers predict what the magnetic field will do. “They will be very happy,” said Di Chiara.
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