Which process involves the breakdown of rocks into smaller particles due to environmental factors?

Weathering is the process that breaks down rocks into smaller particles as a result of environmental factors. This process can occur via physical mechanisms, such as freeze-thaw cycles, where water infiltrates cracks in rocks, freezes, expands, and eventually causes the rock to fracture. Chemical weathering also plays a significant role, where minerals in the rock react with water, acids, or other substances, leading to the alteration of the rock's composition and structure.

Unlike metamorphism, which involves changes in the mineral structure and composition of rocks due to heat and pressure deep within the Earth's crust, weathering does not require such conditions. Crystallization refers to the formation of solid crystalline structures from a liquid or gas, which is unrelated to the breakdown of rocks. Diagenesis involves changes that occur in sediment after it has been deposited, but these changes are not primarily focused on the breakdown of existing rock materials, making weathering distinctly appropriate for this question.