Which soil classification has a particle size less than 0.002 mm?

• A. Silt
• B. Sand
• C. Clay
• D. Boulder

Answer: (C)

The classification of soil based on particle size plays a significant role in understanding its properties and how it behaves in various environmental conditions. Clay particles are uniquely characterized by their very small size, specifically being less than 0.002 mm in diameter. This size classification is crucial because it defines the physical and chemical characteristics of clay, which differ markedly from larger particle groups.

Clay particles are notable for their high surface area relative to their volume. This property allows them to retain water and nutrients effectively, making them an essential component in soil fertility. Furthermore, the minute size of clay particles leads to unique behavior in terms of drainage and compaction. They tend to compact tightly together, which can create issues with drainage and aeration in the soil.

In contrast, other soil types such as sand and silt are composed of larger particles and have distinctly different characteristics impacting their use in construction, agriculture, and other applications. Understanding clay's specific size classification helps in soil management and informs decisions in practices like land use planning and construction.