Science Facts

Why Does The Sahara Desert Exist – History & Facts

Sahara Desert

The name of Sahara is Arabic that means the greatest desert. The Sahara covers an area of 9.4 million square kilometres and occupies most of North Africa. It covers 11 countries, namely Algeria, Chad, Egypt, Libya, Mali, Mauritania, Morocco, Niger, Western Sahara, Sudan, and Tunisia. The Sahara is surrounded on the west by the Atlantic ocean. An arid, desolate, and primarily lifeless area spans from the Red Sea in the east to the Atlantic Ocean in the west. It is from the Mediterranean Sea in the north to the Sahel in the south. It covers more than 9 million square kilometres or 31% of the continent of Africa.

Like any desert, the Sahara has a significant influence on life within its borders. But because of its size, the desert’s reach extends far beyond. And some of these effects are even visible from space. The atlas mountains and the mediterranean sea in the north. The red sea in the east and Sudan and the niger valley in the south. It is divbeganded into the western Sahara, the central part of the Sahara mountains, the Tibesti mountains, and the Air mountains. These areas of the desert have the highest peaks. The Libyan desert could be considered the driest region. The cities in the Sahara are mostly concentrated around the oases.

Why does the Sahara desert exist?

Today most of the Sahara is devoid of life, but this wasn’t always the case. Believe it or not, the desert cycles between periods of humidity and aridity every twenty thousand years. One of the main reasons for that is the precession of the Earth’s axis, which changes the location of the North African monsoon. As the monsoon position shifts, so does Sahara’s rainfall, and with it, the desert turns green. To no one’s surprise, the Sahara is currently going through a dry period. It has been expanding during the last three thousand years and continues to do through desertification.

  • As the desert grew, it accumulated enough sand to cover the entire globe with a layer 20 centimeters thick.

Because of this vast amount of sand, the Sahara can generate huge dust storms. Such storms can damage human health and have a negative economic impact by eroding soils and damaging crops. However, they can also have beneficial effects through enriching ecosystems. Out of all places globally, these are probably best observed in Central and South American rainforests, which receive most of their mineral nutrients through the Sahara dust. It is carried by air currents over the entire Atlantic Ocean. Looking at the size of the desert storms, you might think that the Sahara consists entirely of dunes, but this is not the case.

  • The dune fields, some of which rise to 180 meters in height, only cover about 15% of the surface.

The rest consists of rocky plateaus, mountains, and large Oasis depressions. Sahara’s highest point, mount Koussi in Chad, is a dormant volcano. It stands at 3450 meters and, despite its altitude, receives little to no precipitation. Sahara’s slowest point, on the other hand, Egypt’s Qattara depression, has somewhat of a more exciting story.

  • At a low point of 133 meters below sea level, there have been several proposals to flood the Qattara depression.

It lies within proximity to the Mediterranean Sea. It was argued that the flooding of the depression could generate power through a hydroelectric turbine while rejuvenating the surrounding desert. However, some concerns flooding the area with seawater could lead to a hypersaline lake. That would not support a fish population or a salt pan that could build up to tens of meters and eventually fill the depression. Regardless of that, people remain optimistic about the plan, and it’s not difficult to understand why. Water is essential for life, and nowhere is that more evident than in the Sahara.

  • The desert spans through the territory of eleven countries with a combined population of 300 million.

But less than 1% of that live in the desert. The areas with the highest concentration of people are near water sources, which is vital for agriculture. Growing crops elsewhere in the desert is nearly impossible, and where vegetation manages to survive, it is very sparse. On top of that, large regions of the desert are hyper-arid and often received no rain for years. Despite the lack of rain, however, the Sahara still contains vast amounts of freshwater leftover from its humid period stored in large sedimentary aquifers deep beneath the surface.

In recent years people have found a way to tap into that water, which is the result. Each about a kilometer across, these crop circles are visible from space and symbolize the success of human ingenuity in the harshest of conditions. The shape of the crop circles results from an efficient center-pivot irrigation system, which draws water from the Nubian aquifer.

  • According to estimates contains 150,000 cubic kilometers of water.

Despite that, the solution is unlikely to turn the whole Sahara into arable land. The problem with fossil water is that it is a non-renewable resource. As such, its increased usage would only result in its faster depletion. This, in turn, would make life impossible for people who rely on it for survival.

How Sahara became a desert?

About 6,000 years or 8,000 years ago when all the Sahara was completely covered in grass. It was a luscious grassland with a lot of vegetation and a wet climate. Earth is tilt which changes the climate. It was tilt from about 22 to about 25 degrees due to the moon. It’s from about 20 to 25 degrees every 40,000 years or so. About 8000 years ago, it changed from approximately 24.1 degrees to 23.4 degrees. So the Sahara region did not receive as much light anymore. Middle of the summer in this particular region received quite a lot of light. It was easier for vegetation to roll here, and because the vegetation grew so much, this also increased the number of monsoon rains.

Vegetation retained a lot of moisture and released it back into the air creating even more rain. So it was like a cycle. However, as the temperature decreased, it got to where the monsoon started to die out. This vegetation started to dry out as well. After about twenty to thirty thousand years, it will again receive a lot more sunlight and so chances for this region to be full of vegetation again.

The tremendous weight helps the speed of the earth’s tilt that the northern and southern poles create due to all of the ice. As the ice cap started to melt, specifically in Greenland, many ice caps started to melt. As these ice caps began to melt, all of the water got distributed into the rest of the oceans. So the northern and the southern pole started to lose a lot of their actual weight. In other words, the natural tilting effect has accelerated and, because of this, will be experiencing more seasonal changes even more frequently.

It has a tremendous effect on weather, specifically on the rain monsoon. That may increase the desertification of other regions. It might not provide enough time for various areas to replenish the vegetation. Climate change is creating specifically the mountain of the caps to shift the planet’s weight around, making the tilting of the axis even faster.

Climate of Sahara

The climate in the Sahara is extremely harsh. In the warmest months of the year, the temperatures regularly exceed 58 degrees celsius that’s over 122 degrees Fahrenheit. The average annual temperature is around 30 degrees Celsius, which is 86 degrees Fahrenheit. Due to insufficient humidity, there are large temperature differences between day and night. So at night, the temperatures regularly go below zero that’s cold.

  • The northeastern parts of the Sahara are characterized by strong winds that reach hurricane speeds and often cause sandstorms.
  • The central part of the Sahara has almost no precipitation. And it’s the driest area of the entire desert with almost no vegetation.
  • In the mountains, precipitation is more abundant, and temperatures are lower.

These so-called winds that blow up to a hundred kilometers per hour are responsible for North Africa’s dry and warm climate. The Sahara is mostly an arid area, and almost half of the Sahara has rainfall of two centimeters per square mile. The rest up to 10 centimeters per square mile. Unpredictable rains are usually very abundant and create torrents.

Flora in the Sahara

The central parts of the Sahara generally have poor vegetation. The northern and southern parts of the desert and the plateaus have sparse grass and desert bushes with occasional trees. It is estimated that about 500 plant species grow in the Sahara. These plants are resistant to high heat and low humidity but tend to survive in saltwater environments.

  • Alexander, Tamarisks, Myrtles, Acacias, and palm trees can be found in the mountains.

These are often plants that grow close to the ground adapted to make the best use of water. But also store it inside, usually through thick leaves or thorns, to prevent water from evaporating.

Animal world in the Sahara

Thousands of years ago, the Sahara had enough water and solid living conditions for various animals and people. There is evidence that crocodiles lived in rivers and caved prehistoric drawings found in Sahara. The giraffes, elephants, cattle, and lions that once lived in the Sahara. Today there are no living conditions in a large area of the Sahara. Exceptions are the Nile valley, several oases, and plateaus in the north of the desert where olives can be grown. The changes occurred some 1,600 years before Christ.

Due to the earth’s axis, it increased temperature and a decrease in precipitation. They are estimated to be about 70 animal species in the Sahara. Camel animals that are a symbol of the Sahara were brought to the Sahara around 200 AD. Their resistance to harsh conditions soon proved to be a significant advantage over the horses that they replaced. Due to their soft feet, camels move quickly through the sand and can last up to 17 days without food or water.

For some animals such as snakes, scorpions, and rodents, the desert climate even suits them. The Sahara is a suitable habitat for very poisonous scorpions and snakes and is home to over 40 species of rodents.

  • Hyenas, jackals, African wild dogs, and the Sahara cheetah are the most dangerous carnivores living in the Sahara.

In the northern Sahara also lives the phoenix fox characterized by its large ears. During the day, she stays in tunnels dug in the sand, and at night, she goes out and hunts for rodents. Desert crocodiles even live in parts of chad. Camels and goats are kept by nomadic tribes and are the only domestic animals in the desert.


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Sources:

“Detection and Analysis of an Amplified Warming of the Sahara Desert”. Journal of Climate.
“Is the World Full or Empty?”. Story Maps. Story Maps.
“Sahara.” Online Etymology Dictionary. Douglas Harper, Historian.
“English-Arabic online dictionary”.
A Dictionary of Modern Written Arabic (Arabic-English) (4th ed.).
“A “pacemaker” for North African climate”.
“Sahara desert”. Terrestrial Ecoregions. World Wildlife Fund.
Ecophysiology of Economic Plants in Arid and Semi-Arid Lands.

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