Why Does the Sahara Change Shape?
The Sahara, the world’s greatest dry hot desert, stretches right across the north of Africa where there is almost no rainfall and, consequently, little or no vegetation to anchor the soil. The sand is blown constantly by the wind, much of it into a landscape of great shifting dunes which constantly change shape, while the edges of the desert eternally encroach upon the land around.
The Sahara is the largest hot desert and the third largest desert in the world after Antarctica and the Arctic. The Sahara extends over three and a half million square miles of land, comparable to the area of China or the United States, where the average rainfall is generally much less than 10 inches a year. The prevailing winds come from the heart of Asia and carry little moisture.
The borders of the Sahara Desert include the Red Sea on the east, the valley of the Niger River and the Sudan on the south, the Mediterranean and the Atlas Mountains on the north, and the Atlantic Ocean on the west. The desert has gone through shifts in temperature and moisture over the past few hundred thousand years. The temperature during the day exceeds 100° F in the summer, and even in the winter averages 60°—70° F. The surface of the sand is sometimes as hot as 170° F. The sun beats down from a clear sky all day, but at night the same cloudless sky allows the land to cool quickly, and there is often frost at dawn in winter.
The wind acts as a great sand-blasting machine, constantly wearing down rocks and carrying sand and small pebbles along. The few desert plants survive because they have long roots or thick fleshy leaves, and stems that reduce water loss and may even store moisture. A desert oasis is simply a place where there is water. The greatest oasis of all is Egypt, where for thousands of years life has depended on the careful use of the waters of the River Nile.
For several hundred thousand years, the Sahara has alternated between desert and savanna grassland in a 41,000 year cycle caused by changes (“precession”) in the Earth’s axis as it rotates around the sun, which change the location of the North African Monsoon. It is next expected to become green in about 15,000 years (17,000 AD). There is a suggestion that the last time that the Sahara was converted from savanna to desert it was partially due to overgrazing by the cattle of the local population.
Interesting Sahara Desert Facts:
The shifts in climate in the Sahara Desert are due to a 41000 year cycle. During this cycle, the earth changes its tilt between 22 and 24.5°.
The Sahara Desert is the third largest in the world. The first two are Antarctica and the Arctic.
The Sahara Desert covers 3.6 million square miles. It is almost the same size as the United States or China.
It is the largest desert in Africa.
Sahara means ‘the greatest desert’ in Arabic.
There are sand dunes in the Sahara as tall as 590 feet.
There have been dinosaur fossils found in the Sahara Desert.
More than 30,000 petroglyphs of animals native to rivers have been found in southeast Algeria in the Sahara.
The Sahara Desert is made up of sand dunes, sand seas, gravel plains, stone plateaus, dry valleys, salt flats, mountains, rivers, streams, and oases.
There is sparse grassland in some parts of the desert including the highlands and northern and southern parts of the desert.
Wind and occasional rain are responsible for forming the landforms in the Sahara, which include sand dunes, dune fields, salt flats, and dry valleys. Land formations change regularly.
The highest point in the Sahara Desert is Emi Koussi. This is a shield volcano in northern Chad.
Most of the streams and rivers in the Sahara are only seasonal. The main exception is the Nile River. It crosses the Sahara and empties into the Mediterranean Sea.
There are several underground water sources called aquifers. They sometimes reach the surface and form oases. Some of these are the Siwa, Kufra, Timimoun and the Bahariva.
The climate of the Sahara is one of the harshest ones in the world.
One half of the Sahara Desert receives less than .79 inches of rain each year. The rest of the desert only receives 3.9 inches per year.
There are several mountain ranges in the Sahara that get snow regularly. It’s not common anywhere else. In 1979 a snowstorm actually stopped traffic in Algeria. It was the first time that snow was recorded in the area. It melted in a few hours. It snowed in Algeria again in 2012.
Goats and camels are the most common domesticated animals in the Sahara.
There are several species of fox in the Sahara, as well as antelope, gazelle, cheetah, monitor lizards, sand vipers, wild dogs and ostrich, among others.
The desert shrinks and grows depending on the climate.
The people who live in the Sahara are mostly nomads. Nomads move from place to place.