The Dynamic Desert

The desert can be very hot or freezing cold. Scientists say that warm deserts are dry and sometimes do not get rain. Warm deserts form about one fifth of the earth's surface. Cold desert temperatures are low. It is covered with snow and ice. These conditions make it hard for plants, animals, and people to survive. There is a desert in Siberia called the tundra. It is the cold kind-of desert. If you see the desert from high above, the desert would like two belts stretching all the way across the earth. The deserts are above and below the equator.

The world's largest desert is the Sahara Desert in Africa. Rainfall ranges from less than 5 inches (12.7 cm) to 10 inches (25 cm) , with dry periods occasionally lasting for years. Nighttime temperatures often drop below freezing, and daytime temperatures have been recorded at over 135Ð F (57ÐC) in the shade.The surface of the desert ranges from sand dunes to gravel surfaces to several deeply dissected mountain massifs. Vast underground aquifers, filled with water, underlie much of the region, and there are important deposits of iron ore, phosphates, oil, and natural gas.

Few plants can survive in the desert because there is not a lot of water. Some plants have long roots to get water from deep underground. Others store water in their leaves, roots, or stems. They have thick bark and waxy leaves to help them save water.

Many insects adapt well to life in the desert. Some have bodies enclosed in tough outer shells. They can sneak into tiny cracks in rocks to protect themselves from the sun. Reptiles are cold-blooded. They need heat from the sun to warm their bodies.

Most desert animals are small and live under rocks during the day. They come out at night to feed themselves. Birds cope well with desert conditions. They have feathers to protect themselves from the heat. They also can fly to find water.