Grains of sand in the million-year-old African desert
Although the sands of the desert may seem to move endlessly downwind, scientists are now discovering that grains of sand from Africa’s Namib Sand Sea have been inhabiting there for at least a million years.
Analysis of the desert sands could shed light on how the climate may have changed over the millennia, the researchers said.
The vast Namib Sea of ââSand, which covers approximately 13,125 square miles (34,000 square kilometers) along the coast of Namibia, is one of the oldest and largest sandy deserts in the world. However, little is known about the origin of its sands, whether they come from distant sources or local sediments. This uncertainty is also true for other large deserts, in large part because one sand dune is very similar to another.
“While much climate research has focused on the polar regions, deserts and in particular sandy deserts remain relatively poorly studied and poorly understood, despite the fact that millions of people live in threatened arid and semi-arid areas. by desertification, âsaid researcher Pieter Vermeesch, a geologist at the University of London, told OurAmazingPlanet.
To track the movement of grains of sand through the sea of ââsand, Vermeesch and his colleagues measured the levels of uranium and lead in the sands to confirm that their main source is apparently the Orange River on the southern edge of the Desert. Namib. They also analyzed the radioactive isotopes produced by cosmic rays (high-energy particles that rain down on Earth from space), which allowed them to estimate how long sand was in the region.
“All the samples were collected from the ridges of large dunes – up to 200 meters (656 feet) high – a pretty intense workout,” recalls Vermeesch.
The researchers found that it took at least a million years for the winds to blow sand across the sea of ââsand.
âWhile geologists have long known that the Namib Sand Sea is a very ancient landform, we had no idea that individual sand grains spent so much time in it,â said Vermeesch. The time the sands spent in the sea of ââsand was 10 times longer than he had expected.
Seas of sand only exist in hyper-arid environments, and therefore their presence or absence can reveal key details about ancient climates. “The residence time of grains of sand in a sea of ââsand is an indicator of the sensitivity of desert areas to climate change,” said Vermeesch.
It remains uncertain whether the sand dunes of the Namib Sand Sea have been continuously active over the past million years or whether they have gone through cycles of stasis and movement. âTo answer this question, additional samples will be needed in the heart of the desert,â Vermeesch said.
Ultimately, Vermeesch wants to use these techniques to investigate the Sahara. “Due to political instability in the region, relatively little is known about the Sahara and the sediments it contains,” he explained. “It is unfortunate, because a better understanding of the Sahara would lead to a better understanding of human evolution, of the spread of humans out of Africa, of the negative feedback mechanisms that dust production in the Sahara has on global warming. , etc. Important discoveries await to be made in this part of the world. “
Scientists detailed their findings online Oct. 31 in the journal Nature Geoscience.
This article was provided by OurAmazingPlanet, a sister site of LiveScience.