Final answer:
Soil is formed from weathered rocks and decomposed organic material, which combine to create a mixture that undergoes further development influenced by climate, organisms, and other factors over time. The formed soil consists of distinct layers called horizons that contribute to soil fertility and functionality.
Step-by-step explanation:
The formation of soil is a complex process that occurs over long periods of time. The correct answer to the question "Which of the following best describes how soil is formed?" is A. from weathered rocks and decomposed organic material. This process involves the physical and chemical weathering of rocks, which breaks them apart and produces mineral particles such as sand, silt, and clay. These mineral components are typically mixed with organic matter, which includes decaying plant and animal material. Over time, this combination of mineral particles and organic material, along with the influence of climate, organisms, and relief, leads to the formation of the various horizons present in a mature soil profile.
Soil originates from the parent material, which can either come from weathered bedrock or from materials transported to the location by water, ice, wind, or gravity. The parent material undergoes further weathering and mixing, contributing to the soil's characteristics and fertility. The presence of organic matter, or humus, in the topsoil enriches the soil, supports microbial activity, and enhances moisture retention, which are crucial for plant growth.
The layers of soil, known as horizons, each play a role in soil function. The organic-rich O and A horizons serve as the primary regions for plant production, while the B horizon, or subsoil, accumulates fine material that has moved downward from above. The C horizon includes the parent material in its broken-down form, leading to the eventual development of soil.