The Sahara Desert, spanning across 11 countries in North Africa, is the largest hot desert globally. Although it's now a harsh arid region, it was once a lush tropical area. Scientists have discovered that the desert's transformation may have been caused by human activities, such as overgrazing, around 8,000 to 4,500 years ago.
Fossil findings in the Sahara have also provided insights into the evolution of whales. In the Western Desert of Egypt, geologists discovered fossils of whales that lived on land, with some specimens having feet. These findings suggest that whales evolved from terrestrial mammals that gradually adapted to life in the ocean.
The Sahara is also home to the Eye of the Sahara, a geological formation resembling a bull's eye. While initially believed to be an impact crater, it's now thought to be a geologic dome. Some researchers even propose that it could be the remnants of the lost city of Atlantis, described by Plato.
Additionally, the Sahara has yielded mysterious objects like the Clayton ring, a conical pottery cylinder found in the Dakhla Oasis in Egypt. These rings, used by nomadic herders, remain an enigma, with their purpose and significance still unknown.
Here are the key facts extracted from the text:
1. The Sahara Desert is located in Africa and spans across 11 countries.
2. The Sahara Desert is the largest hot desert in the world, covering an area of 9 million square kilometers.
3. The Sahara Desert covers about a third of the African continent.
4. The Sahara Desert is surrounded by the Atlantic Ocean on the west, the Red Sea on the east, the Mediterranean Sea on the north, and the Sahel Savannah on the south.
5. The Sahara Desert has sand dune fields, mountains, plateaus, sand- and gravel-covered plains, salt flats, basins, and depressions.
6. The Sahara Desert was once a tropical area, but it became a harsh arid region due to fluctuations in the Earth's orbital axis.
7. The African Humid Periods, which occurred at repeated intervals throughout Earth's history, brought more energy and rain to North Africa.
8. The transition from humid to dry occurred rapidly in some areas, resulting in the formation of the Sahara Desert as we know it today.
9. Archaeologist David Wright found that the presence of pastoralists and their domesticated animals corresponded with changes in plant types and varieties.
10. Wright concluded that overgrazing by humans and their animals may have triggered the end of the humid period and the formation of the Sahara Desert.
11. Fossils of whales have been found in the Sahara Desert, dating back 37 million years.
12. The fossils found in the Sahara Desert include those of Basilosaurus and Dorudon, two types of ancient whales.
13. The Eye of the Sahara, also known as the Richat Structure, is a geological formation in the Sahara Desert that resembles an enormous bull's eye.
14. The Eye of the Sahara is approximately 40 kilometers wide and is located in Mauritania.
15. Geologists initially believed that the Eye of the Sahara was an impact crater, but further studies revealed that its origins are entirely Earth-based.
16. The Eye of the Sahara is a geologic dome that contains rocks at least 100 million years old.
17. Some scientists believe that the Eye of the Sahara may be the remains of the lost city of Atlantis.
18. The Clayton ring is a conical pottery cylinder open at both ends, found in the Sahara Desert in Egypt.
19. Clayton rings were used by nomadic herders inhabiting the Dakhla Oasis during Egypt's first dynasties.
20. The function of Clayton rings is still unknown.