Soil is formed from the weathering of rocks and minerals. The surface rocks break down into smaller pieces through a process of weathering and is then mixed with moss and organic matter. Over time this creates a thin layer of soil. Plants help the development of the soil.
In NSW it is a different story. It provides guidelines to parents and says a child aged 10-12 years can be left for up to 12 hours but not between 10pm and 6am. They must have a back-up adult available and can look after one or two other smaller children.
State laws vary quite a bit. Some states, including Texas, have not set a minimum age. Others, including Oregon, set a minimum age of 10 years old, while states like Maryland do not allow parents to leave a child under the age of 8 alone at home or in a car. Some states set a minimum age for babysitters as well.