The function of soil is far more important than just the dirt beneath your feet. Not only is good quality soil essential to agriculture and our environment today, but soil is also a major source of information used by archaeologists to learn about our past. For example, depending on the soil type and acidity, artefacts such as bone, shell, and pottery can be preserved for thousands of years in certain soils.
Soil formation is a slow process; a single inch of topsoil can take 500 years to form. There are five key soil-forming factors: the parent material, climate, organisms, topography and time. The process begins with the weathering of primary soil material, or parent rock, which can be bedrock, an older soil surface, or sediments transported and deposited by winds, glacier movement or other water flows. The climate – in the form of heat, ice, wind, water and many other environmental forces – has a strong impact on the weathering of this parent material and the formation of soil. Once a thin layer of soil has developed, organic life and other plants help bind the material by spreading their roots through the soil to bind it, moving through the earth to aerate it and producing waste materials to enrich it.
The shape of the landscape also affects how the parent rock is weathered. For example, if the soil is forming on a slope, factors such as the steepness of the slope, the direction in which the slope faces, and the way the water drains all affect how the soil develops. And perhaps the most important factor in the formation of soil is time. The soil profile is continually changing and developing with time and well developed horizons (see ‘soil profile’
illustration) can take thousands of years.