Notes
Weathering breaks down rock at or near the surface without moving it far.
- Mechanical (physical) weathering breaks rock into smaller pieces with no change in composition: frost wedging (water freezes and expands about 9%), root growth, abrasion, thermal expansion.
- Chemical weathering changes the minerals: water, carbon dioxide (carbonic acid), oxygen (oxidation, rust) and acids. Limestone dissolves in weak acid.
- Breaking rock into pieces increases surface area, speeding up chemical weathering.
- Warm, wet climates have the fastest chemical weathering.
Practice
Water seeping into cracks, freezing and expanding is called:
Freezing water expands and widens cracks.
Iron-rich rock turning reddish-brown from rust is an example of:
Iron reacts with oxygen.
Why does crushing a rock into small pieces speed up chemical weathering?
More surface means more contact with water and air.
Ready for more? Take the Unit 5 test.