Weathering alters the earth’s surface by breaking down rocks into fragments, allowing particles to drift away. There are two main types of weathering: mechanical and chemical. Mechanical weathering happens by purely physical means, while chemical weathering occurs through chemical reactions. Both mechanical and chemical weathering can be further divided into subgroups based on cause.
The most common form of mechanical weathering, ice expands in cracks of rocks, making the cracks larger and eventually breaking the rocks to pieces.
After rain water fills rocks, it sometimes evaporates rather than freezes. This leaves salt behind, which grows into larger crystals. These crystals form wedges that snap the rock apart as a process of mechanical weathering.
When dissolved carbon dioxide in moisture creates carbonic acid and reacts with minerals in the rock, carbonation occurs. This weakens and breaks down the rock as a chemical weathering process.
Hydrolysis, a type of chemical weathering, happens when a chemical reaction occurs between hydrogen in rain water and the minerals in a rock, softening the rock.
Oxidation takes place when oxygen combines with water and metallic earth minerals, turning the surface rock a reddish-brown. Another word for this type of chemical weathering is “rusting.”