Soil formations occur from thousands of years of weathering of rock. There are three main types of soil formations that occur: sand, silt and clay. These formations are dependent on type and quantity of rock, moisture and location. Climate is the most important factor in soil formations. Soils from different locations will show distinctive characteristics. Soil formations are characterized by weight, color and texture, and can change over a period of time.
Clay is formed from the weathering of silicate-bearing rocks. This type of soil takes thousands of years to form. It consists of fine-grained materials and hardens when it dries or is fired. Clay was once used to make the first writing tablets. It is often referred to as a hard soil. Very little can grow in clay without it being improved. Clay is very low in organic matter, so the first step in improving clay is adding organic fertilizer back into it. Clay can rarely become a perfect growing medium but it can be improved upon.
Sand is a granular soil formation that is made from finely divided rock and minerals. It is generally classified according to size. Sand is grainy between the fingertips and is the next size up from silt, which feels like powder between the fingers. The white sand that can be found at beaches is made primarily of ground-up lime with a small amount of ground shells. The most common component of sand is silica, which is the most abundant mineral in the Earth's crust. Sandy soils are frequently used for such crops as watermelon and peaches, because they have excellent drainage qualities.
Silt is a granular rock formation that is between sand and clay in size. Silt is composed mostly of quartz and feldspar. It is made from the chemical decomposition or sanding of rock formations. This rock formation is often referred to as rock flour or stone dust. This dust is lightweight and often carried by rivers, streams or water currents in the ocean and even as dust in the air.