Soil is formed from the parent rock material by

• Chemical decomposition is the process by which rocks are broken down into smaller pieces by chemical reactions. These reactions can be caused by acids, bases, or other chemicals.
• Physical decomposition is the process by which rocks are broken down into smaller pieces by physical forces, such as weathering and erosion.
• Biological decomposition is the process by which rocks are broken down into smaller pieces by living organisms, such as plants and animals.

All of these processes work together to form soil. The type of soil that is formed depends on the type of parent rock material, the climate, and the vegetation.