The World's Deserts

What Is a Desert?

Picture a land where rain almost never falls. The sun beats down, the ground is dry and cracked, and water is harder to find than gold. This is a desert.

A desert is any place that gets very little rain — usually less than 25 centimetres in a whole year. That is the real secret of a desert: not heat, not sand, but dryness.

When people think of deserts, they often picture endless golden sand dunes. Some deserts do look like that. But many are rocky, stony or even icy. In this book we will explore deserts hot and cold, meet the clever creatures that live there, and find out how anything survives with so little water. Let's set off into the dry lands!

How Deserts Form

Why are some parts of the world so dry? There are a few reasons, and they all come down to where the rain does — and does not — fall.

Many of the biggest deserts sit in wide bands north and south of the equator. Here, the air sinks down from high in the sky. Sinking air is dry air, so very little rain falls and a desert forms. The Sahara and the Australian deserts are like this.

Other deserts form behind tall mountains. When wind blows toward the mountains, it drops its rain on one side. By the time it crosses to the other side, the air is dry. The land beyond is left in what is called a rain shadow, and a desert can form there.

Some deserts are simply very far from the sea, so the wet ocean air never reaches them.

Hot Deserts and Cold Deserts

Not all deserts are baking hot. Deserts come in two main kinds.

Hot deserts, like the Sahara, are scorching during the day. But here is a surprise: at night they can become very cold, because there are no clouds to trap the day's heat. So a desert traveller might sweat in the daytime and shiver after dark.

Cold deserts are dry but cold most of the time. The Gobi Desert in Asia has freezing winters. And the largest cold desert of all is Antarctica. It is covered in ice, yet it gets almost no snowfall, so scientists count it as a desert.

The Sahara: A Sea of Sand

The largest hot desert in the world is the Sahara, which stretches across the top of Africa. It is almost as big as the entire United States.

Parts of the Sahara are covered in huge sand dunes that can be taller than buildings and that slowly move with the wind. But much of the Sahara is actually rocky and stony, not sandy at all.

Here and there, water bubbles up from underground to make a green, leafy spot called an oasis. An oasis is a precious place in the desert, where palm trees grow and travellers can rest and find water.

Deserts Around the World

Deserts are found on every continent. Let's visit a few of the most famous.

The Arabian Desert in the Middle East is another vast sea of sand. The Gobi Desert stretches across Mongolia and China and is famous for the dinosaur fossils found buried in its rocks.

The Atacama Desert in South America is the driest place on Earth. In some parts of it, no rain has been recorded for many years. In North America, the Mojave and Sonoran deserts are home to towering cactus plants.

Australia has huge red deserts in its centre, an area Australians call the Outback.

How Animals Survive

Deserts are tough, but they are far from empty. Many animals have clever ways to survive the heat and the lack of water.

The camel is the most famous desert animal. It stores fat in its hump for energy and can travel for days without drinking. Its long eyelashes and closable nostrils keep out blowing sand.

Many small animals, like the fennec fox with its huge ears, hide in cool burrows during the hot day and come out at night. The fox's big ears help it lose heat and stay cool. Lizards, snakes and scorpions are well suited to the dry heat. Some desert creatures get nearly all the water they need from their food and almost never drink at all.

How Plants Survive

Plants have to be clever too. With so little rain, every drop of water is precious.

The cactus is a desert expert. Instead of thin leaves, which would lose water, it has sharp spines. It stores water inside its thick, juicy stem, swelling up after rare rains so it has water to last through the dry months.

Other desert plants grow very long roots to reach water deep underground, or spread their roots wide to catch every drop of rain. Some seeds wait patiently in the dry ground for years. Then, after a rare rainfall, they burst into life, and the desert suddenly blooms with flowers.

People of the Desert

People live in deserts too, and they have learned amazing ways to cope.

For thousands of years, nomads — people who move from place to place — have crossed the deserts with their camels, goats and tents. The Bedouin of Arabia and North Africa and the Tuareg of the Sahara know where to find water and how to travel safely across the sand. They wear loose, flowing robes that keep them cool and protect them from the sun and blowing sand.

Today, some deserts also have large, modern cities. With wells, pipes and machines that can take the salt out of seawater, people have brought water to dry lands and built thriving towns where once there was only sand.

What We Learned

We have crossed the great dry lands of the world! Let's remember what we found.

A desert is a place that gets very little rain — that is the real secret, not heat or sand. Deserts form where dry air sinks, behind tall mountains, or far from the sea. They can be hot, like the Sahara, or cold, like the Gobi and even icy Antarctica. Clever animals like camels and foxes, tough plants like the cactus, and resourceful people like the Bedouin have all found ways to thrive where water is rare.

Deserts show us that life can find a way, even in the driest corners of the Earth.

Ready for more adventures? Roam every part of the planet in The Seven Continents, or climb high in Mountains of the World.