Sand is one of the most common substances on earth. Sand is made up of very small pieces of rock. If the grains of sand are larger than two millimeters, it is called gravel.
Sand is formed over many years from rocks that weather. Most sand is made of quartz, a mineral. Other sand comes from the rocks of volcanoes.
However, sand also comes from animals or plants. Mussels, for example, have a shell made of the same material that eggshells are made of. Small pieces of shells or the remains of coral often make up part of the sand, especially on beaches or in the river bed.
There are different types of sand: The grains of desert sand are round and have smooth surfaces. You can see that clearly under the microscope. When the wind blows them around, they rub against each other. The grains of sand from the sea, on the other hand, are angular and have a rough surface.
However, sand is not only found in deserts, on coasts, and on the seabed. In every soil, there is a proportion of sand. If the earth contains a lot of sand, it is called sandy soil. They are quite common in Europe.
What do people need sand for?
People today need huge amounts of sand to make concrete from it. This also requires cement, water, and other chemical additives. They use concrete to build houses, bridges, and many other structures.
But you can only build with sand from the sea. The grains of desert sand is too globular and do not form strong concrete, no matter how much cement. On many coasts and in many parts of the sea there is no more sand because it has been used up. Sand is therefore fetched from far away in large ships, often even from another continent.
Many people like it when there is a lot of sand on the beach. Sometimes sand is piled up for this. This is of little use, however, because the current carries the sand away again. You have to keep refilling it fresh.
Because sand gives way, when you jump long distances you often end up on an area of sand. Playground equipment is often built in hollows in the sand so that a child is less likely to get injured if it should fall. You can also make something out of the sand. This applies to a sandbox for playing and also to a statue made of sand.