How the Sahara Desert Formed How deep is the sand? What's underneath?

 

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 Is it a gradual transition or is it all pure sand?

The Sahara, which means desert in Arabic, extends across North Africa. The Sahara is the world's largest non-polar desert, covering over 9,000,000 km², the size of the United States.

Although the Sahara is famous for its sand dunes, most of the surface is made up of hamada or rocky plateau. The Sahara's stunning dune fields only cover about 15% of the entire desert surface and are found mostly in the north-central region. In the dune areas of Algeria and Libya, the depth of the sand varies because the dunes can build up to several hundred meters high, but then change as the sand shifts.

The desert expanse is dominated by barren, rocky expanses with dry hills and valleys.

What many people don't know is that the Sahara was once a fertile area that supported thriving human communities. A study of core samples has revealed that the ancient climate of North Africa underwent rapid desertification and climate change that transformed the region from a humid, subtropical landscape to a desert in a matter of years. This occurred around 4200 BC and returned to the same desert conditions that dominated the area 13,000 years earlier.

As the climate began to change, the Sahara region became arid and vegetation died out. With nothing to hold the soil in place, wind action was able to remove all the fine sediment until only sand and rock remained.

PROBABLE CAUSE

The transition from the mid-Holocene climate to the current one was driven by changes in the Earth's orbit and the tilt of the Earth's axis. About 9,000 years ago, the Earth's tilt was 24.14 degrees, compared to today's 23.45 degrees, and perihelion (the point in Earth's orbit closest to the Sun) occurred in late July, compared to early January. At that time, the Northern Hemisphere received more summer sunlight, which amplified the African and Indian summer monsoons.

The changes in Earth's orbit occurred gradually, while the climate and vegetation of North Africa evolved rapidly. German researcher Claussen and his colleagues believe that various feedback mechanisms within Earth's climate system amplified and modified the effects of the orbital changes. By modeling the impact of climate, oceans, and vegetation both separately and in various combinations, the researchers concluded that the oceans played only a minor role in the desertification of the Sahara.

DIFFERENT

Wadi El Hitan (Whale Valley), in Egypt, contains the fossil remains of an extinct suborder of whales. The valley was evidently part of a shallow marine basin 40-50 million years ago. Desertification has helped preserve and reveal a huge amount of fossils.


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I drilled over 1000 bore holes in the Sahara for oil exploration. For the most part there is nothing there but sand stone and rock. The Sahara had some vegetation millions of years ago in a few areas long enough to form oil. But it is very rare there.

There was a wet period. Didnt last long. Not from rain but from melting ice from the glaciers in the Highlands. The melting of these glaciers also formed the Nile Flood plain and the Nile Delta.


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