Research press release


Nature Geoscience

Geoscience: Earth’s mantle motion has kept Nile stable for 30 million years



今回、Claudio Faccennaたちは、現在の排水路が初期に確立したことを示唆する、地球ダイナミクスモデルおよび現在の地質学的・地球物理学的証拠を提示している。彼らは、対流セルがおよそ3000万年前から地球マントル内で動き出し、エチオピアの下で上昇流と地形の隆起、そして地中海東部の下で沈降に関連した下降流をもたらし、これが現在の排水路のパターンにつながったことを見いだしている。

The drainage pathway of the River Nile has persisted over the past 30 million years, because a conveyor-belt-like motion, or ‘convection cell’, in the Earth’s mantle has stabilized surface topography according to a paper published in Nature Geoscience.

Drainage systems of large rivers have long been a puzzle, and two competing possibilities were suggested for the evolution of the River Nile. In one scenario, river flow from Ethiopia to the Mediterranean has been active for the past 30 million years. Alternatively, drainage pathways at that early time led from Ethiopia westward towards the Congo Basin or northwestward towards the Sirte basin, and a connection to the Mediterranean was established much later, about 5 to 8 million years ago.

Claudio Faccenna and colleagues present geological and geophysical evidence as well as simulations with a geodynamical model that suggest an early establishment of present-day drainage pathways. They find that since about 30 million years ago, a convection cell has operated in the Earth’s mantle, with upwelling and topographic rise beneath Ethiopia and downwelling associated with sinking under the eastern Mediterranean Sea, which led to the current drainage pattern.

doi: 10.1038/s41561-019-0472-x

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