Gravel Driveway Basics. Cost: $1 to $5 per square foot, though installation costs vary widely depending on where you live and the type of base required. Durability: Lifetime, with proper maintenance. Type of gravel: This depends on your area, but angular shapes are preferred over round.
Soil minerals form the basis of soil. They are produced from rocks (parent material) through the processes of weathering and natural erosion. Water, wind, temperature change, gravity, chemical interaction, living organisms and pressure differences all help break down parent material.
In Soil Time. Soil formation is a continuous process. A thin soil in the northern hemisphere may have taken 15,000 years to develop. A mature soil in a warmer climate may be millions of years in the making but can now replenish much more quickly. In human terms, most soil is ancient.