Soil is formed by the combination of physical, chemical and biological processes in which huge rocks are broken down into smaller particles over a long period of time.

Rocks undergo a process of expansion and contraction in which they expand during the day and contract during the night due to the constant rise and fall in temperature.

However, not all parts of a rock undergo expansion and contraction at the same rate, resulting in the formation of cracks.

Gradually, these cracks cause the rocks to break down into smaller pieces.

With time, these smaller pieces convert into particles and form soil.

Water plays an important role in soil formation.

Water that gets collected in the cracks of rocks sometimes freezes, which helps in widening the cracks.

Also, flowing river water helps in the wearing down of rocks over time, which results in the formation of soil.

Strong blowing winds also rub against rocks and help in wearing them down.

Lastly, some living organisms like lichens, that grow on rock surfaces release certain substances that cause rock surfaces to powder down and form a thin layer of soil.