Weathering

Weathering is the breakdown of rocks, soils, minerals, and even wood and artificial materials through contact with water, atmospheric gases, sunlight, and living organisms, occurring in place without the material being carried away. Physical weathering breaks rock apart mechanically, through temperature swings, the expansion of freezing ice, the release of pressure, and the growth of salt crystals, without changing its chemical makeup; chemical weathering occurs when water, oxygen, carbon dioxide, and other substances react with a rock's minerals and convert them into different, secondary minerals; and biological weathering adds the mechanical and chemical effects of soil microorganisms, lichens, fungi, and plant roots. Weathering is distinguished from erosion by whether material moves: weathering breaks rock down where it stands, preparing it for erosion, the actual transport of that broken material by water, ice, wind, waves, or gravity.