Soil Particle Size

Michigan Environmental Education Curriculum
Groundwater Supply

The behavior of water in the ground is influenced by the type of soil present.  Soils are classified according to their particle size as follows:

There are several different systems in place that denote the particle sizes.  The values given above pertain to the USDA Soil Taxonomy system.  You probably have a good idea of what gravel and sand particles look like, but maybe not silt or clay.  Silt particles are about as big as the thickness of your hair, and clay particles are much smaller than that!

Generally, soils consist of a mixture of different particle types, such as "sandy clay", or a "silty sand".