Chemical weathering occurs when rocks and minerals break down due to chemical reactions. Three main causes of chemical weathering are:
- Water: Water, especially when slightly acidic (due to dissolved carbon dioxide forming carbonic acid), can dissolve minerals in rocks. For example, water can break down feldspar into clay minerals through hydrolysis, a common process in chemical weathering.
- Oxygen: Oxidation, a reaction with oxygen, can change minerals, particularly those containing iron. Iron-rich minerals like olivine and pyroxene can rust (oxidize) when exposed to oxygen and moisture, turning them into minerals like hematite or limonite.
- Acid Rain: Acid rain, which forms when sulfur dioxide (SOâ‚‚) and nitrogen oxides (NOâ‚“) from pollution combine with water vapor in the atmosphere, can significantly accelerate chemical weathering. The acidic rain can dissolve minerals like calcite in limestone, leading to the erosion of rocks and the formation of features like caves and sinkholes.
These processes work together to break down rocks and minerals over time, altering the Earth’s surface.