Soil is the thin layer of loose material that forms the surface layer of the Earth, and it is a mixture of many different things including rock, minerals, water, air, and organic matter. Soil is important for life on Earth because it provides a place for plants to grow, holds water in place for their roots, and contains nutrients needed for their growth. Soil also provides a home for many animals and other living things.

Soil forms slowly, and a layer of soil that is 1 inch thick may take 500 to 1,000 years to form. Soil is made up of layers that rest on solid rock called bedrock, and different types of soil contain different mixtures of clay, silt, and sand. There are many kinds of soil, and each kind of soil has big and small rocks in it and some humus.

Soil performs many critical functions in almost any ecosystem, whether a farm, forest, prairie, marsh, or suburban watershed. There are seven general roles that soils play:

• Soils serve as media for growth of all kinds of plants.
• Soils modify the atmosphere by emitting and absorbing gases (carbon dioxide, methane, water vapor, and the like) and dust.
• Soils provide habitat for animals that live in the soil (such as groundhogs and mice) to organisms (such as bacteria and fungi), that account for most of the living things on Earth.
• Soils absorb, hold, release, alter, and purify most of the water in terrestrial systems.
• Soils serve as engineering media for construction of foundations, roadbeds, dams, and buildings.
• Soils are a record of past climates, organisms, and landscapes.
• Soils are a source of extractable materials, such as ores and clay, which are used for ceramics, construction, and industrial processes.

In summary, soil is a complex mixture of minerals, water, air, organic matter, and countless organisms that are the decaying remains of once-living things. It is the "skin of the earth" and is capable of supporting plant life and is vital to life on earth.