ABSTRACT
The nature of soils Soils are formed when pre-existing rock masses, the “parent” rock, is broken down and disintegrated by environmental processes. There are three kinds of processes:
— Physical: temperature changes and the action of water, wind or glaciers break rocks down. Changes in temperature cause expansion and contraction at different rates in different minerals, producing internal changes and fissuring. Water can break rock down in several ways: (i) by eroding fragments; (ii) by freezing, directly producing internal stresses due to the increased volume of ice compared with water; (iii) by alternating wet/dry cycles over time. These physical actions break down the parent rock into smaller fragments which are then separated by active agents, such as water, wind or gravity, and transported to other sites where they are eroded further. This means that physical activity creates rock particles which further disintegrate to form soil.
