Exploring the Sahara
by Sarah Canzoneri
The Sahara is huge—the largest desert on Earth. It covers about 3.5 million square miles in North Africa. That is about as big as the whole United States. Some scientists think that the Sahara will shrink by the year 3000.
The word sahara is an Arabic word meaning “desert.” Arabic is the language spoken in much of North Africa.
The southern part of the Sahara is grassy and not as dry. It is called the Sahel, which is Arabic for “shore.”
The world's highest official temperature was recorded in the Sahara in September 1922. It was 136°F in the shade!
Sand dunes cover only a small part of the Sahara. Most of the desert is bare rocks or gravel. There are also mountains, and some of them are covered by snow in winter. The highest point in the Sahara is Mount Koussi, which is 11,204 feet high.
About 1,600 species of plants grow in the Sahara. Some must stretch their roots as far as 80 feet into the ground to find water. The plants grow mainly in parts of the Sahara where the most rain falls. In the driest parts of the desert, there are no green plants for 120 miles.
Animals that live in the Sahara have adapted to the harsh conditions. The small fennec fox has large floppy ears that help it cool off. The addax, an antelope with long, curvy horns, rarely drinks any water. Instead, it sucks moisture from the grasses and bushes that it eats.
People brought camels to the Sahara almost 2,000 years ago to replace horses. That was a good idea because camels are better suited for desert life. A camel can go for as long as 17 days without eating or drinking. It also has soft feet that can move quickly and easily through the sand. Camels' thick coats keep them cool as well as warm.
Today, the Sahara gets very little rain, but there is a lot of water under the desert. Rain that fell thousands of years ago stays underground in pools called aquifers. There are about 4 billion gallons of water under the Sahara. People drill wells more than 1,000 feet deep to get it.
Sahara dust is blown across the Atlantic Ocean. Some scientists think chemicals or diseases in the dust could be killing coral reefs in the Caribbean.
Dunes are mounds of sand that have been blown and shaped by the wind. Dunes can be as big as a tall hill. Some dunes move across the desert, but some stay in one place and become “fossilized”—hard and permanent.
There are different types of dunes. When the wind blows in one direction, long curved dunes called barchan dunes form. When the wind blows from two directions, long, straight dunes called linear dunes form. When the wind comes from several directions, star dunes form. From above, these dunes look like a star, and they can be more than a thousand feet high.
Exploring from the Sky
Can someone explore the Sahara without going there? Yes. In fact, some of the most exciting discoveries about the Sahara have been made using “explorers” high in the sky—satellites. Thanks to these sky-high explorers, we know more about the history of this amazing desert.
The satellites send down images, or pictures, of Earth. Some are taken by the SIR-A radar system. It can make images that show what is under the ground, below the sand. These images have shown geologists that, in ancient times, there were lakes, mountains, and valleys where the Sahara is now.
So, the Sahara was not always a forbidding desert. Long ago, dinosaurs and giant crocodiles lived there. After the dinosaurs became extinct, giraffes, elephants, hippos, and other animals lived in the Sahara. So did people. They were shepherds and hunters who had small villages and farmed the land. There were forests and grasslands in the Sahara.
Then, about 6,000 years ago, the climate began to change. Within a few centuries, the Sahara became the desert that it is today. Why? Scientists think that conditions in the atmosphere changed so that the Sahara got warmer and drier. As the climate changed, fewer and fewer plants grew there, and the people had to move to places where there was more water.
Satellite images help people make other discoveries in the Sahara. With these pictures, archaeologists can find where ancient people had their settlements. Paleontologists—scientists who study fossils to learn about prehistoric life—use satellite images to help them find the best places to search for clues to life millions of years ago.
- How would you describe the climate of the Sahara?
[anno: The climate is hot and dry.]
- How has the climate of the Sahara changed from the time that dinosaurs lived in the area?
[anno: The Sahara used to be a place where there were forests and grasslands. Then the conditions changed, and fewer plants grew. Now it is a desert.]
- How is the Sahara possibly affecting another part of the world?
[anno: Scientists think that chemicals and diseases in dust blown from the Sahara across the Atlantic Ocean to the Caribbean may be killing some of the coral reefs in the Caribbean.]