1. weathering: breaking down of rock can be mechanical or chemical

2. mechanical: rock broken down into smaller pieces by physical processes
does NOT change the chemical composition of rock
***same minerals***

3. main agents of mechanical weathering are:
ice
gravity
and
plants and animals

4. frost wedging: water seeps into cracks then freezes
puts pressure on rock until it breaks (ice)

5. exfoliation: rock breaks into curved sheets that peel away from the rock
due to a release of pressure from overlying rock (called unloading) as rain has loosened the layers (water)

6. organic activity: mechanical weathering by a living organism
plant roots grow into rock cracks then break the rock as the roots grow larger

7. animals dig and burrow to break rock
earthworms bring small fragments to the surface which weathers them quicker

8. ***removes OR changes the types of minerals***
chemical: rock broken down by chemical processes
changes the composition of rock
***removes OR changes the types of minerals***

9. water carbon dioxide oxygen main agents of chemical weathering are:
and
oxygen

10. water is the main agent by absorbing or dissolving other materials that affect the rocks
any minerals dissolved in the water are moved elsewhere

11. this is how limestone weathers
when carbon dioxide from air dissolves in water, it forms carbonic acid
this is how limestone weathers

12. oxygen combines with water to cause the outer layer of rock to look darker in color (oxidation = rust!)

13. chemical weathering can change the physical shape of rock
water seeps into cracks (called joints) first
this weathers the corners and edges of rock more rapidly so gets a rounded look

14. is called spheroidal weathering
joint
NOT exfoliation because minerals have changed

15. all rocks don’t weather in the same way
differential weathering: where different parts of a large rock mass weather at different rates

16. Shoals’ Jug Rock!

17. rock composition
rocks with softer minerals (like calcite) = faster weathering
rocks with harder minerals (like quartz) = slower weathering

18. surface area
more surface area (fractures, joints, smaller pieces) = faster weathering
less surface area (larger pieces) = slower weathering

19. climate
alternating periods of hot & cold weather = faster weathering
humid (wet) weather = faster weathering