In the soil profile, you can see how there are different layers, which a soil scientist calls horizons. She is using the orange nails to show you where the different horizons are. Originally, all soil comes from rocks and minerals. Over time, rocks and minerals fall apart, or weather, into smaller and smaller pieces, and form soil. The soil scientist has marked 6 different soil horizons in the profile.
Soil horizons are layers of soil that are formed under different conditions or environments.
She picked them by color , texture , and structure .