Names of Soils

Clay

• Soil formation begins with rock. Over time, the weathering action of wind and rain and the reaction of acidic chemicals cause rock to break down. The particles of the rock change size, shape, and chemical composition.

  Silicate-bearing rock breaks down into fine mineral compounds called phylosillicates. These fine mineral particles are what all the types of clay are made of.

  The two main types of clay are determined by where they are found. Primary clay, called Kaolin, is clay that stays where it was formed. Secondary clays, called sedimentary clays, are transported away from the primary site by erosion and water.

Silt

• Silt is formed by the weathering of quartz or granite into fine particles. These particles are larger than the particles in clay but smaller than sand particles. Often, silt is formed by the erosive action of glaciers crushing stone as they move. Sedimentary action leaves deposits of silt at the bottom of lakes, rivers, and oceans.

  The weathering action on the quartz or feldspar causes sand-sized particles to split along their crystal lattice, forming silt. Silt is often called rock flour or stone dust.

Sand

• One way soil is classified is by particle size. Sand is soil created by the weathering of stone and minerals, with particles ranging in size from 0.0625 mm up to 2.0 mm. Sand can contain many different minerals as well as particles of coral and shells from animals living in the sea.

  Sand is a very useful soil. Farmers use it to help aerate the soil for plant growth. In industrial settings sand is used to make glass and concrete. Sand is used to provide roads and train rails with better traction to reduce accidents.

Topsoil

• The layer of soil commonly found on the top of the Earth is topsoil. Topsoil is a combination of sand, silt, clay, and decayed vegetable matter and is good for the growth of plants.

  Topsoil is formed slowly over time by the action of weathering combined with the effects of plants and animals. Plants die and decompose into humus. The movement of plant roots, burrowing creatures, and earthworms combines and aerates the soil mixture into the rich dark topsoil favored by farmers everywhere.