Weathering is the breakdown of rocks and other materials associated with three main processes:
• physical (cracking in rocks caused by impact, movement, changes in temperature, or the long-term effects of wind and water movement)
• chemical (leaching, dissolving),
• biological (action of roots and biota)
A micron, also known as a micrometre (symbolized as µm), is a unit of length equal to one millionth of a metre or one thousandth of a millimetre. It is commonly used in scientific and engineering fields to measure very small objects, such as the thickness of a human hair or the size of bacteria.