Dry as a Desert Dry as a Desert Deserts are dry! How dry? An area is defined as a desert if it gets only 10 inches of rain, or less, per year. Amazingly, deserts are found on every continent throughout the world. In the tropics, deserts can get really hot as there are few clouds to block the heat of the sun. But not all deserts are hot. Deserts that are farther away from the tropics actually get cold. It even snows in some cold deserts during the winter! Dry as a Desert North Africa's Sahara is the largest hot desert in the world with temperatures reaching 122 degrees Fahrenheit (50 degrees Celsius) during the day. The Gobi desert in Asia and the desert on the continent of Antarctica are examples of cold deserts. Most people think of deserts as vast expanses of sand dunes, but deserts of rocks and stone are in fact far more common. Desert sand started out as rock, which over the ages was weathered (worn down) to form particles. The finer the particle, the farther it can be blown by wind or carried by floodwater from the rare rains.

Making a Dune Making a Dune Wind flows over mound of sand Making a Dune Only about 10% of the world’s deserts are completely covered by sand. In these places, the wind blows the sand into many shapes. Sometimes the crest, or top, of a sand dune builds up so high that it will collapse just like an ocean wave. Crest gradually builds up Making a Dune Sand is carried by the wind for short distances, but even the strongest wind only lifts sand grains about 3 ft (1 m) off the ground. A sand dune begins to form where there is an obstacle, such as a plant, which slows down the wind and makes it drop its load of sand. As the sand accumulates, it forms a bigger barrier to the wind, causing more sand to be dropped. Namib Desert

Welcome Water Welcome Water Imagine miles of sand stretching as far as the eye can see. Then, in the middle of all that sand, a cooling pool of water appears. Are your eyes playing tricks on you? No, it’s an oasis! An oasis forms when water from deep underground reaches the surface in the desert. Towns often spring up around these life-giving sources of water. If an oasis is big enough, it can even support crops such as date palm trees. Welcome Water Some parts of the desert are not dry and barren: occasional rainfall turns pockets of the desert green and fills dry riverbeds with floods of water. Some of this water is trapped behind small dams or, after it has seeped underground, is tapped by means of wells dug into the riverbed. Water from deep layers of rock comes to the surface at oases, where crops such as date palms are cultivated. With the help of various irrigation methods, more of the desert can be cultivated. Today vast areas of the desert are green as a result of pumping water from deep bore wells. But there is a danger that underground water may run dry, especially when more people settle in the desert and when crops needing a large amount of water are grown. Rock Oasis Water flows up cracks in rock

Desert Blooms Desert Blooms The desert may look like an empty place—but it’s actually home to many plants and animals. How do these living things survive in such a dry place? They have special adaptations, or traits, that help them. For example, these cactus plants store water in their fleshy stems. They are also covered with a waxy layer that prevents water loss. What other adaptation do both of these plants share? Desert Blooms Some plants and animals survive in the desert by avoiding the driest times, only growing or becoming active after occasional rains. Plants exist in the dry soil for years as seeds. When the rains come, it may take several good soakings before the seeds germinate. This prevents seeds from germinating unless there is enough water for them to flower and produce seeds. Succulents are plants that survive dry conditions by storing water in their fleshy stems or leaves. Cacti are the best-known succulents, with their bizarre-shaped stems varying from globes growing close to the ground to tall skyward-pointing branched forms. They are mainly found growing wild in the Americas but are not restricted to deserts. Other desert succulents show a great variety of forms, including some which look remarkably like cacti. The spines on cacti are actually modified leaves that protect the plant from grazing herbivores and help conserve water. Prickly pear cactus After a rare desert rain, both cactus plants bloom with flowers. Hedgehog cactus

Night Stalker Night Stalker Snakes are well adapted to desert life. This red spitting cobra hunts its prey at night to avoid the heat of the desert day. It also has scaly skin to preserve water. Desert reptiles have another advantage. They are cold-blooded. This means they control their body temperature by gaining or losing heat from their surroundings. So snakes don't have to eat as much food as birds and mammals do to maintain a constant body temperature. This is a handy adaptation in an environment where food is scarce. Night Stalker Reptiles, such as snakes, lizards, and tortoises, do well in deserts because they control their body temperature by gaining or losing heat from their surroundings. This means that reptiles need not expend as much energy as birds and mammals, which use lots of energy to generate heat within their bodies. So reptiles need less food, a scarce commodity in deserts. Using less energy also means that reptiles do not breathe as frequently as birds and mammals do, and this helps them to conserve moisture. Compared to amphibians, such as toads, with their permeable skins, reptiles are better suited to the desert because they have scaly skin to help them conserve moisture. The red spitting cobra spreads its hood before spitting venom to defend itself. When attacking its prey, mainly small reptiles and mammals, the cobra bites to inject venom. Like many desert snakes, it hunts at night to avoid the heat of the day. The red spitting cobra is native to Africa.

Ship of the Desert Ship of the Desert Camels have been carrying people and goods through the deserts for thousands of years. These “ships of the desert” can go days without water. They also store fat in their humps which their body can use for energy when food is scarce. Look at all the special adaptations that help the camel survive. From its long eyelashes to its tough feet, this animal is well adapted for its desert home. Long eyelashes keep sand out Fur in ears keeps sand from getting in Ship of the Desert Camels carry people and goods through the driest of deserts, under the burning sun and through swirling sandstorms. They can go for days without water: they have few sweat glands and conserve moisture because their body temperature can rise many degrees before they start to sweat. They also produce concentrated urine and dry dung. Camels eat tough desert plants, and survive for long periods by using the fat stores in their humps. There are two kinds of camel: the dromedary, with one hump, and the Bactrian camel, with two humps. Both kinds have been domesticated, but only the Bactrian camel continues to live in the wild. Dromedary Camel Long legs keep the camel’s body high off the ground where the temperature can be 18 degrees cooler than at its feet. Tough soles on feet can withstand high temperatures