Soil is a surface mixture of rocks, minerals, organic matter, water, and air. Soil is a surface mixture of rocks, minerals, organic matter, water, and air.

The rocks and minerals come from weathering. The rocks and minerals come from weathering. The organic matter is called humus, which comes from the decay of different life forms in or on the soil. The organic matter is called humus, which comes from the decay of different life forms in or on the soil.

Water is from precipitation Water is from precipitation Soil air is from the atmosphere. Soil air is from the atmosphere.

Rocks, minerals, and organic matter form soil particles (~ 50% of a soil by volume). Rocks, minerals, and organic matter form soil particles (~ 50% of a soil by volume). The spaces between soil particles are called soil pores The spaces between soil particles are called soil pores (~ 50% of a soil by volume). (~ 50% of a soil by volume). Water and air fill the pores. Water and air fill the pores.

Over time, soils develop horizons, distinct layers of soil identified by color, texture, and particle structure. Over time, soils develop horizons, distinct layers of soil identified by color, texture, and particle structure.

O: Decaying organic matter on soil surface (fallen leafs). A: Loose dark surface soil good for food production (topsoil).

B: Dense light-colored sub- surface soil not good for food production (contains rocks). C: Mostly partially weathered rocks and minerals (bedrock).

A variety of living things live in soil. A variety of living things live in soil. Used for food production. Used for food production. Used for construction (adobe) and fuel (peat). Used for construction (adobe) and fuel (peat). Used for types of waste treatment. Used for types of waste treatment.