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Sahara changed from wet to dry every 20,000 years



A new study suggests that climatic conditions in the Sahara Desert have gone from wet to dry about every 20,000 years.

The study was conducted by scientists from the Massachusetts Institute of Technology (MIT). The results were published in the journal Progress of science. The research was funded in part by the National Science Foundation.

The Sahara Desert is known as one of the hottest, driest and most sorry regions of the world. It covers about 9.3 million square kilometers in North Africa.

But previous evidence suggested that the Sahara had not always experienced such conditions of extreme heat and drought. The evidence included material collected from fossils and rock paintings of the region.

The evidence showed that the Sahara had sometimes evolved into a very humid climate. This allowed plants and animals to grow and develop and led to the creation of human settlements.

Now, MIT researchers have found more evidence of this changing climate. Scientists have examined dust accumulated on West African shores over the past 240,000 years. Research has shown that during this period, the climate of the Sahara changed between wet and dry about every 20,000 years.

A man stands near his hut in the desert region of Tenere, Niger, in south-south-central Ténéré, Wednesday, May 30, 2018. (AP Photo / Jerome Delay)

A man stands near his hut in the desert region of Tenere, Niger, in south-south-central Ténéré, Wednesday, May 30, 2018. (AP Photo / Jerome Delay)

David McGee is Associate Professor in the Department of Earth, Atmospheric and Planetary Sciences at MIT. He helped lead the study.

McGee said MIT News the new evidence supports the idea that the climate of the region has changed repeatedly over the years. "Our results suggest that the history of the North African climate is mainly the 20,000-year-old beating back and forth between a green Sahara and a dry Sahara, "he said.

McGee and other researchers have reported that these two-way climate changes were mainly due to changes in the Earth's axis as the planet circled the sun. This process affects the amount of sunlight between seasons. Research suggests that every 20,000 years the Earth receives more intense summer sunlight.

When the axis of the Earth changes again, the amount of sunlight is reduced. This study revealed that the change of season took place continuously every 20 000 years. The other part of the season was conducive to the monsoon, creating a wetter, greener and more plant-rich environment. When the rainy activity weakens, the climate becomes hot and dry, like the rest of the Sahara today.

Scientists have based their research on dust samples taken from the ocean sediment. They said that hundreds of millions of tons of Saharan dust had accumulated over hundreds of thousands of years deep in the Atlantic Ocean, off the coast of Africa. from the West.

A tire used as a road marker is hanging on a tree in the desert region of Ténéré, Niger, in south-central Niger, on Sunday, June 3, 2018. (Photo AP / Jerome Delay)

A tire used as a road marker is hanging on a tree in the desert region of Ténéré, Niger, in south-central Niger, on Sunday, June 3, 2018. (Photo AP / Jerome Delay)

Examination of dust accumulation has allowed researchers to become familiar with the history of climate in the Sahara Desert. Samples contained layers ancient sediment accumulated over millions of years. Each layer could contain traces of Saharan dust and remains of life forms, MIT News reported.

This information was used to estimate the dust formation period. This led to the general conclusion that Saharan changes in dry wet climates occurred every 20,000 years.

Researcher David McGee said MIT News that today we only see the Sahara Desert as an extremely sorry people and "inhospitableThe new study suggests that the climate of the region has "tilted between grasslands and a much wetter environment and a return to dry climate, even in the last quarter of a million years."

McGee says that he thinks the latest research may be useful for studying the history of the Sahara with respect to human settlement. "How good could it have been for humans to settle in the Sahara Desert and cross it for disperse out of Africa, against inhospitable moments like today, "he said.

I am Bryan Lynn.

Bryan Lynn wrote this story for VOA Learning English, based on a study published in Science Advances and a report by MIT News. Hai Do was the editor.

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Words in this story

sorry adj. an empty, lonely and sometimes sad place

fossil not. part of an animal or plant from there are thousands of years preserved in the rock

dominant adj. main or most important

sediment not. solid substance that forms a layer at the bottom of a liquid

layer not. a quantity of a substance covering a surface, one on the other

inhospitable adj. not nice or easy going because of extreme conditions

disperse v. to separate and go in different directions


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