What are the two main processes that contribute to soil formation?

Weathering and biological activity are the two fundamental processes driving soil formation. Weathering (both physical and chemical) breaks down parent rock material into smaller mineral particles that form the inorganic component of soil. Physical weathering creates fragments, while chemical weathering alters the minerals' composition, making nutrients more available to plants. Biological activity introduces the organic component—decomposing plant and animal matter creates humus, while living organisms from bacteria to earthworms physically mix soil layers, create spaces for air and water, and chemically modify minerals. Plant roots break up rock and contribute organic matter when they die. Microorganisms decompose organic material and help cycle nutrients. Together, these processes transform rock into the complex, living medium we call soil, though complete soil formation can take thousands of years depending on climate, parent material, topography, and organisms present.