For thousands of years, the the Nile fertilized the valleys along its winding path through northeastern Africa, anchoring ancient civilizations and still serving today as a major transport and irrigation route.
But the age of its venerable waters, which extend over 4,225 miles (6,800 kilometers), was the subject of debate. A group of experts claimed that the river was born about 6 million years ago, when a drainage system changed course, while another group five times more old as that.
A new study finds evidence to support this latest theory: the Nile could have emerged about 30 million years ago, driven by the movement of the Earth's mantle – the thick layer of rock between the core and the earth's crust, reported today a group of researchers (11 November) in the newspaper Nature Geoscience.
Related, connected, related: Photos: 3,400 year old grave along the Nile
The Nile is thought to have formed at the same time as the Ethiopian highlands, said the main author, Claudio Faccenna, a professor at the Jackson School of Geosciences of the University of Texas. One of the main tributaries or branches of the Nile, called the Blue Nile, is found on the Ethiopian highlands.
The Blue Nile brings most of the Nile water – and most of the sediment that it contains – to join the other tributary of the Nile (White Nile) in Sudan, before to jump into the Mediterranean Sea.
Faccenna and his team had previously analyzed the sediments collected in the Nile delta – the land created during sediment deposition at the river's meeting with the Mediterranean – and compared their composition and age to those of the ancient volcanic rock found on the Ethiopian plateau. They discovered that the sediments and rocks were paired and were between 20 and 30 million years ago, suggesting that the river was formed at the same time as the plateau.
The researchers therefore sought to know how the river could be connected to the mantle of the Earth, as suggested by the theory, Faccenna explained to Live Science. In the new study, Faccenna and his colleagues created a 40-million-year-old computer simulation of the Earth. tectonic plates – a theory that suggests that the outer envelope of the Earth is cut into pieces that move and slide on the mantle.
Their simulation showed that a warm mantle plume – a recrudescence of extremely hot rocks in the mantle – pushed the soil upward, thus creating the Ethiopian highlands, and also activated a "treadmill" still existing in the mantle that was growing upward on the southern Ethiopian highlands. and pulls the ground in the north. This creates a slope to the north, on which the Nile is still flowing, said Faccenna.
It's hard to know if the Nile has changed course during his life – even slightly – and it's something that Faccenna and his team hope to discover in the future. They also want to implement this method to analyze how the mantle may have also altered the course of other rivers in the world.
Originally published on Science live.