Here's why:
* Chemical weathering involves chemical reactions that break down the minerals in rocks. This can involve processes like:
* Oxidation: The reaction of minerals with oxygen, often forming oxides (like rusting iron).
* Hydrolysis: The reaction of minerals with water, breaking down the mineral structure.
* Carbonation: The reaction of minerals with carbonic acid (formed when carbon dioxide dissolves in water), dissolving some minerals like limestone.
* Acid rain: Rainwater that has become acidic due to pollutants can react with minerals and cause significant weathering.
* Physical weathering, on the other hand, breaks rocks down into smaller pieces without changing their chemical composition. Examples include:
* Frost wedging: Water freezing and expanding in cracks.
* Abrasion: Rocks rubbing against each other.
* Thermal stress: Alternating heating and cooling of rocks causing them to break.
In summary, chemical weathering changes the mineral composition of rocks through chemical reactions, while physical weathering only changes their size and shape.
