Soil covers much of the land on Earth. It is made up of minerals (rock, sand, clay, silt), air, water, and organic material (matter from dead plants and animals). Soil provides a substrate for plants (roots anchor in soil), a source of food for plants, and a home for many animals (insects, spiders, centipedes, worms, burrowing animals, bacteria, and many others).
A scientist who studies soil is called a pedologist.
Types of Soil: There are many different types of soils, and each one has unique characteristics, like color, texture, structure, and mineral content. The depth of the soil also varies. The kind of soil in an area helps determines what type of plants can grow. There are 12 orders (types) of soil: Alfisols, Aridisols, Entisols, Histosols, Inceptisols, Mollisols, Oxisols, Spodosols, Ultisols, Gelisols, Andisols, and Vertisols.
Soil Formation: Soil is formed slowly as rock (the parent material) erodes into tiny pieces near the Earth's surface. Organic matter decays and mixes with inorganic material (rock particles, minerals and water) to form soil.
Soil Horizons (layers): Soil is made up of distinct horizontal layers; these layers are called horizons. They range from rich, organic upper layers (humus and topsoil) to underlying rocky layers ( subsoil, regolith and bedrock).