What is the break up of rocks by air/water?

• A. Mechanical Weathering
• B. Chemical Weathering
• C. Biological Weathering
• D. Erosion

Answer: (B)

Chemical weathering is the process by which rock is broken down through chemical changes caused by interactions with air and water. When minerals in rock react with water, dissolved gases, and acids in the environment, they dissolve or transform into new minerals, weakening the rock. Think of rainwater that’s slightly acidic from dissolved CO2 dissolving minerals like calcite, or water that hydrolyzes feldspars into clay minerals. Oxygen in the air can also react with minerals like iron, turning them into rust and altering the rock’s integrity. This is different from mechanical weathering, which breaks rocks into smaller pieces without changing their chemical composition (physical breakup from freeze-thaw, abrasion, etc.). Erosion, meanwhile, describes the movement of those weathered fragments away from their source. Biological weathering involves organisms contributing to breakdown, such as roots widening cracks or lichens producing acids. So the breakup by air and water specifically points to chemical weathering.