Some cystists believe that the Nile River can unravel the mysteries of the mantle beneath it.
There is an objection to the age of the Nile – whether it was formed by a river diverting about 5 million years ago or whether protoil flowed through the area for 30 million years. If the Nile is older, as one of the team of scientists attests, then this may be a reflection of the flow of the mantle material circulating beneath it. The mantle le is the largest layer of Earth consisting of a high-pressure rock beneath the crust and above the nucleus.
"Maybe we can use rivers to understand how the mantle flows" as a whole, Claudio Faczenna, the first study author and professor at the University of Texas at Austin, tells Gizmodo.
Two competing models attempt to explain the Nile. In one of them, the Nile was formed when a drainage basin changed course from west to north about 6 million years ago, due to the same processes that formed a crack in the African tectonic plate called the East African Gap. Another theory says that the river was formed 30 million years ago as a result of prolonged geological processes in the mantle that propel the earth up into Ethiopia and down closer to the Mediterranean.
A team of researchers from the United States, Canada, Italy and Israel presented new evidence in favor of the latter theory, including data and modeling. Modeling how local topography changes over time suggests that the Ethiopian Plateau may have begun to expand 30 million years ago as the earth began to sink down into the eastern Mediterranean from the mouth of the Nile. Researchers associate this model with one of the mantle moving like large slabs of rock, displaced around, according to the book published today in Nature Geoscience.
Previous research by this team also supports the older Nile. An analysis of rocks from 20 to 30 million years old, called zircons discovered at the mouth of the Nile, showed that they appear to coincide with the rocks found in the Ethiopian Plateau at the source of the Nile, suggesting that the river is at least as old . The thickness of the sediment as well as the amount of erosion in the Blue Nile (one of the main tributaries of the Nile) also seems to support the older age.
Age aside, researchers say they have demonstrated that some rivers can serve as a tool to understand mantle behavior below. Some rivers usually originate in mountains or high plateaus, but others, such as the Nile or the Yenisei River in Siberia, simply start in places with higher land where the earth mantle is pushed up. These types of rivers differ in the type of sediment they deposit at their mouth (usually of volcanic origin, from the mantle tip ).
This work is exciting for scientists like Faccenna who hope to better understand the mantle which is difficult to study because of its depth at crust . "If we could find another signal for the deep mantle on the surface, it would be incredible," he told Gizmodo.
Obviously, this work is model-based, so there are built-in human assumptions that can alter its result. But I really like the idea that there are rivers on Earth that we can use as windows in the underworld.