1. Forces That Shape Our Earth: UNIT 3: WeatheringAndErosion

2. Weathering & Erosion:  Erosion and weathering are major forces that shape Earth’s surface.  For example, the Grand Canyon was formed through erosion by the Colorado River running through it!

5. What is weathering? Weathering: The breaking down of rocks into smaller pieces. 1. Mechanical /Physical 2. Chemical Hulk Rock Smash!

6. So what is erosion? Erosion: The movement of weathered rock by wind, water, glaciers & gravity

8. Types of Weathering: Mechanical/Physical: Rock is physically broken into smaller pieces (larger pieces become smaller pieces of the same rock) Chemical: Rock is chemically changed (like rusting or dissolving away)

9. 5 Agents of Mechanical Weathering: 1. Water 2. Freezing & Thawing 3. Animal Actions 4. Plant Growth 5. Wind 6. Gravity

10. Water  As water flows over rocks it breaks off the rough edges and causes them to be smooth or carves away parts of the rock creating holes.

11. Result of Weathering by Water

12. Freezing & Thawing When water in the cracks of rocks freezes it expands causing the crack to enlarge or get bigger. The ice melts & refreezes over & over, breaking the rock apart.

13. Result of Freezing & Thawing

14. Animal Actions  Animals dig (burrow) through the ground to make their homes. This loosens the soil & breaks apart rocks.

16. Plant Root Growth Plants roots can grow into cracks in the rock, slowly breaking them apart.

18. Wind Sand and other rock particles in wind can wear away exposed rock surfaces. Sand and other rock particles in wind can wear away exposed rock surfaces. Like sandblasting or sandpaper on wood Like sandblasting or sandpaper on wood

21. Gravity  Gravity pulls down rocks or sediment from high places and when it hits other rocks it will cause them to break into pieces.  Could be caused by landslides or rockfalls.

22. Results of Gravity

23. Chemical Weathering The process that breaks down the surface of rock by chemical changes.

24. 5 Agents of Chemical Weathering 1. Water 2. Oxygen 3. Acid Rain

25. Water  Water dissolves rock  Water is the most important cause of chemical weathering

27. Oxygen  Oxygen + Water + Iron = Rust through the Chemical reaction called Oxidation  Rock will become crumbly, soft, and appear reddish-brown in color

28. Rusted rock on hillside

29. Acid Rain  Acid rain causes rocks to weather very rapidly.