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Scientists find why eternal Nile has kept its path since humans remember

Roman allegory of the river Nile, the longest river on Earth and the nurturer of the ancient Egyptian dynasties (Piazza del Campidoglio, Rome). Photo: Janericloebe / <a href="https://commons.wikimedia.org/"target="_blank">Wikimedia Commons</a>

It is the Earth’s mantle movement that keeps the river on course / The river is 6 times older than previously thought

The Nile’s unchanging path has been a geologic mystery because long-lived rivers usually move over time. Researchers at The University of Texas at Austin have cracked the case by linking the river’s flow to the movement of rock in the Earth’s deep mantle. In the course of their investigation, they found that if it weren’t for the mantle movement keeping the river on course, the Nile would have turned west long ago, probably changing the course of history along with it.

Another finding was that the eternal river is much older than anyone realized, with the scientists estimating the age of the Nile to be 30 million years – about 6 times as long as previously thought.

The results also provide evidence that the slow movement of the deep mantle is one of the key forces shaping our Earth’s landscape and geological processes. The Earth’s mantle is composed of solid rock that flows like a fluid over long periods. Like currents in an ocean, different areas of the mantle have different circulation patterns.

In the paper, the researchers coompare the tilted nature of the Nile’s topography with a conveyor belt of mantle rock pushing up against the Ethiopian Highlands in the south and pulling the surface down in the north. From beginning to end, the gentle gradient keeps the Nile on a consistent northward course.

The research involved tracing the geological history of the Nile by studying ancient volcanic rock in the Ethiopian Highlands and correlating it with enormous deposits of river sediment buried under the Nile Delta. This told the researchers that after rising dramatically, the Ethiopian Highlands have remained at a similar height for millions of years, which the researchers attribute to the support of the mantle rock from below.

The Nile on its course of about 6650 km ending in a giant delta in the Mediterranean. Source: Hel-Hama / <a href="https://commons.wikimedia.org/"target="_blank">Wikimedia Commons</a>

„We know that the high topography of the Ethiopian plateau was formed about 30 million years ago,“ Becker said. Until now, however, it was unclear how this topography has been maintained for so long.

The team verified their findings using computer simulations that re-created 40 million years of Earth’s plate tectonic activity.

The model showed the arrival of a hot mantle plume that probably led to the outpouring of lava that formed the Ethiopian Highlands while activating a conveyor belt in the mantle that persists to this day. The simulation reproduced changes in the landscape almost exactly as the scientists had expected – including small details in the landscape such as whitewater rapids found along the length of the Nile.

The team now hopes to apply the technique to other rivers such as the Yangtze and Congo. The research was supported by NASA and a grant from the Italian government’s Ministry of Education, University and Research.

The research team included Jackson School scientists Petar Glisovic, who is now a research collaborator at the University of Quebec; and Thorsten Becker, a professor at the Jackson School and research scientist at its University of Texas Institute for Geophysics, where Faccenna is also a research scientist. Other collaborators include researchers from the University of Florida, the University of Milano-Bicocca, the Geological Survey of Israel and the Hebrew University of Jerusalem.

The team now hopes to apply the technique to other rivers such as the Yangtze and Congo. The research was supported by NASA and a grant from the Italian government’s Ministry of Education, University and Research.

Source: University of Texas at Austin

(19.11.2019, USA: 11.19.2019)