What describes biological weathering?

• A. The chemical alteration of minerals by water.
• B. The breakdown of rocks caused by living organisms, such as plant roots or burrowing animals.
• C. The physical breakdown of rocks by gravity.
• D. The deposition of soils on rock surfaces.

Answer: (B)

Biological weathering is the breakdown of rocks caused by living organisms. Plant roots can grow into cracks and push rocks apart, while burrowing animals and microbes can physically disrupt rock or produce acids that help dissolve minerals. This makes the process driven by living organisms, distinguishing it from purely chemical weathering (driven by water and chemical reactions) and purely physical weathering (caused by mechanical forces like gravity or temperature changes). Deposition of soils on rock surfaces isn’t weathering itself—it’s related to soil formation and surface cover.