179121479125786First_Children__s_Encyclopedia

253 Worn by wind Strong winds can lift sand off the ground and blast it hard against rocks. The rock is worn into strange shapes ...

254 Soil is the thin layer of loose material on the land. Soil contains minerals, air, water, and decaying organic matter. Soil ...

255 Soil erosion When soil is farmed too much, its nutrients get used up. The topsoil blows or washes away. Not many plants can ...

The ground holds many useful things, from fuels like coal and oil, to drinking water, and building materials. These valuable ite ...

Creating concrete Concrete is an important building material. It is a mixture of sand, gravel, cement, and water. All these ingr ...

258 Earth is often called the blue planet because 75 per cent of its surface is covered in water. Most of the Earth’s water is s ...

259 Estuary life An estuary is the wide part of a river where it nears the sea. When the tide comes in, salt water flows into th ...

260 Water is constantly on the move, between oceans, land, air, and rivers. This movement is called the water cycle. The water c ...

261 Groundwater In the water cycle, some water seeps underground, where it collects in rocks and sometimes forms pools in caves. ...

262 Planet Earth is wrapped in a thin layer of air called the atmosphere. Without this protective blanket of gases, life on Eart ...

263 Into thin air Like everything else, air is pulled by gravity. Most air molecules are pulled close to the ground, where the a ...

264 Is it sunny or rainy? Is there snow on the ground or a thunderstorm brewing? People are always interested in the weather bec ...

265 Stormy weather Lightning strikes when electricity builds up in clouds. The electricity is created when ice crystals in the c ...

266 People around the world use energy for many different purposes – from powering cars, to heating homes. Most of this energy c ...

267 The energy crisis The remains of plants and animals that lived millions of years ago. Rising energy needs As the world’s pop ...

Space holds many secrets. It contains places where human beings can be stretched into spaghetti shapes, or boiled, or frozen sol ...

What is space? Curiosity quiz Look through The Universe section and see if you can identify the pictures below. Why is space so ...

Earth is cloaked in a thin layer of gases – the atmosphere. Outside this atmosphere is space, where there is no air to breathe, ...

Where does space begin? We call it air.^271 If (^) y ou cou ld dri ve (^) a car (^) str aig ht up , (^) it (^) w ou ld tak e Spa ...

272 The universe The Earth and its moon Earth, our home in space, has one natural satellite, our moon. The moon is about one qua ...