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Students will learn to list the three texture groups in which soils are classified. They will also learn to classify a soil sample as sandy, silty, or clay soil.
Soils are composed of mixtures of mineral and organic materials, but are classified according to the size of their mineral particles. The three main texture groups are sandy, silty, and clay.
Sandy soil contains particles that can be seen with the naked eye and feels gritty when rubbed between the thumb and forefinger. Sandy soils will generally not stick together when wet.
Silty soil contains particles, which are smaller than sand particles but larger than clay particles. Silt feels powdery when rubbed between the thumb and forefinger. Silty soil sticks together when wet, but will not hold its shape after it is dry.
Clay soil contains the smallest particle size. Clay particles form a sticky soil when wet and will generally hold a shape after drying. Soils are rarely composed of just sand, silt, or clay. They are usually a mixture of the three with a larger percentage of one size of particles.
Sund, R. Tillery, Trowbridge, B.; Elementary Science Discovery Lessons: The Earth Sciences; 1973
This lesson plan was provided by the Utah Museum of Natural History.