A few months ago, I wrote here about the Negev Sea of Sand along Nahal Halavan, so arriving at the Moroccan Erg Chebbi was not an unfamiliar landscape, although it is much larger than in the Negev.
Sahara is Arabic for desert. Erg Chebbi between Erfoud and Marzouga in east Morocco it is at the western outskirts of the Sahara Desert, the world’s biggest hot desert, located in eleven countries in North Africa, stretching from the Atlantic Ocean in the west to the Red Sea in the east. In numbers the distance from east to west is 4800 km, and 1200 km from north to south, huge.
Since 1920 the Sahara Desert has increased by 10%; data from Mali shows that the desert moves south at a speed of 48km/year.
An erg is a large area of moving sand; moved by strong winds like we felt it every afternoon. A better description for an erg is a sea of sand, it goes on forever like an ocean, you cannot see the end of it. The dunes here are up to 180 meter in height.
The dunes have different shapes according to the directions of the winds: crescent, linear, transverse, star or dome dunes; but that may be good for a scientific description, I just think they are beautiful with the play of sunlight and shadows.
The sand dunes constitute only 25 % of the Sahara Desert; the rest of the desert are plains of hamda, gravel, sand, plateaus, mountains, rocks.
Hamda
History of the Sahara Desert:
Once upon a time north of Africa was covered by the Tethys Sea which also covered Israel. Movements of the tectonic plates with the African plate crashing into the Euro-Asian plate caused an uplift and drying out of the Tethys Sea, creating the Mediterranean Sea and the Alps. An estimate is that the Sahara has existed for at least 7 million years as a dust bowl where the Tethys Sea was.
One definition of a desert is an area with less than 250mm of annual precipitate; another definition is an area with less precipitate than evaporation, leaving it dry and arid with minimal vegetation, that allow the sand to blow in the wind.
When rare rain occurs, it is often very intense that the rain cannot penetrate into the ground, causing flash floods that cause further erosion of the soil.
We had rain but it barely wet the ground.
Rare rain
Huge amounts of small sand dust particles (sized: PM 10-2.5 µm) are released into the atmosphere and blown with the winds to faraway places, like importantly to the Amazon in Brazil, transported at a height of up to 3- 4 km, easily identified from space as ‘atmospheric rivers of dust’ (or the Saharan Air Layer), in the last few days such a huge dust river is spreading over the Atlantic to Middle America.
It appears that the initiating event of such sand dust storms are thunderstorms, causing cold surface winds (haboobs); these dust particles are smaller than the size in sand dunes. It is estimated that 180 million tons of dust is transported across the Atlantic Ocean each year. These dust particles are rich in minerals and nutrients and is an important natural fertilizer for the Amazon rainforest.
The dust may also land in the ocean causing a fest for alga and plankton, giving sea wild life a rich feeding ground, but an excessive amount will cause overgrowth of blooming algae, that may deplete the sea from oxygen and create a dead zone.
On a global scale the UN estimates that Sahara Desert is the source of 50% of all world dust emissions. On one hand the dust has a positive effect on Earth’s biology, but the air pollution has a negative impact on human health; so, it is a mixed blessing, just like everything in biology it has to be balanced and controlled; just enough, not too much not too little.
Another interesting fact about the Sahara Desert is that it has climate swings: every 20,000 years it alternates between a very dry climate as now, as it has been since the end of the glaciers’ era in Europe, to a more humid and wet climate where the desert becomes like a savanna with more vegetation. This is data derived from sand cores dug out of the Atlantic Ocean covering about 250,000 years. The change in climate is caused by small changes in the tilt of the earth, getting closer to the sun, which then influences the amount of monsoon rain over the Sahara.
One reason the desert is very cold at night is the sky has no clouds and lack of moisture in the air, so the heat is released. We slept in camp of tents, each with bathroom and shower (glamping), inside the tent we did not feel the strong winds outside nor the sand.
Waking up at 5 am to ride a camel to see the sunrise, we really needed sweaters and a jacket. A very nice experience.
Camels, ‘the ships of the desert’
‘The ships of the desert’ is very appropriate considering that the erg is called ‘a sea of sand’.
Camels developed in north America 45 million years ago and is a close family member to the lama that went to south America. The early camels crossed the Bering Isthmus about 3-5 million years ago and spread throughout Asia; 3000 years ago, it was domesticated in today’s Saudi Arabia.
The hump is fat tissue so the camel can go several months without food, but has to drink at least once a week, and then it can drink 30 gallons of water in a few minutes!
It came by right next to my window in the car; it did not spit; it was mildly curious about who I was
Adapted to the desert by having wide feet to walk on sandy rocks and prevent sinking into the loose sand; the long legs keep the body far from the hot ground. Thick eyebrows and long eyelashes catch the sand blowing in the air. The thick fur keeps it warm in the cold nights; it can produce up to 12 liters of milk per day for up to 9-18 months after giving birth. Here in the Negev the Bedouins believe in the curative abilities of camel milk for every ailment you can think of.
Before the camels arrived in the Sahara, the Berbers, people of the desert, had crossed it with oxen, but the camels revolutionized the crossing.
The ‘salt route’ from Marrakech to Timbuctoo took 52 days, the caravans could be up to 20,000 camels carrying salt, gold, ivory, slaves and of course ideas like Islam, along the way there are of religious learning, including a very big library in Timbuctoo.
At 5am it is cold and dark
Sunrise
My attempt to write a haiku about this part of the trip:
Riding my camel
On orange waves of the Sand Sea;
Cold before sunrise.
Yours truly!
Comments