Earth
All places on Earth are made of, or are on top of, rocks. The outside of the Earth is usually not uncovered rock. Over 70% of the Earth is covered by seas full of salty water. This salty water makes up about 97% of all Earth's water. The drinkable fresh water is mostly in the form of ice. There is only a small amount (less than 3%) of fresh water in rivers and under the ground for people to drink. The air above the Earth stops the water from going away into outer space. Also, much of the land on Earth is covered with plants, or with what is left from earlier living things. Places with very little rain are dry wastes called deserts. Deserts usually have few living things, but life is able to grow very quickly when these wastes have rainfall. Places with large amounts of rain may be rain forests. Lately, people have changed the environment of the Earth a great deal. As population has increased, so has farming. Farming is done on what were once natural forests and grassland.