1. Changing the earth’s relief Evolution of the landscape Textbook p. 314, 333-335

2. Changing the earth’s relief: mountain formation Relief = shape of the earth surface Formation of mountains = Orogenesis  through convergent tectonic plate movements  mountain: - steep slopes - at least 600m high Mountains in the making: ➔ Himalaya, Rocky mountains, Alps

3. Laurentians Rocky Mountains Why are they different? ?

4. Montreal streets : After the winter: worn down

5. Laurentians Rocky Mountains Laurentians a lot older  have been worn down ! Why are they different? ?

6. Weathering Gradual destruction of rock on the earth surface. http://www.youtube.com/watch?v=z2nwiba0 N0Y http://www.youtube.com/watch?v=z2nwiba0 N0Y

7. Mechanical weathering The power of water: Rock is fragmented, but not changed in its composition

8. Mechanical weathering Fragmentation of rock through: - Variations in temperature and pressure - water example: freeze thaw cycle of water -wind Composition of rock does not change

9. Minerals in rock are dissolved and changed. Chemical weathering

10. Chemical Weathering Dissolving and changing minerals in rocks  Composition of rock changes. Through: - washing out of certain minerals  enhanced through acid rain

11. Biological Weathering Living organisms destroy rock.

12. Biological weathering Plant roots can break rocks Living organisms release acids  changes and weakens the rock

13. Practice: what kind of weathering? 1. Mechanical 2. Chemical 3. Mechanical + Chemical 1 2 3

15. Water erosion

16. Glacial erosion

17. Wind erosion

18. Erosion of soil Soil Erosion rates on farmed land between 17 and 40 tons per ha and year average natural soil production only 1 ton per ha and year !!!

19. Journey’s end: Deposition

20. The three stages of Erosion Erosion 1.) Weathering 2.) Transport: water, wind, ice 3.) Deposition: in lake, stream, ocean

21. Changing the earth’s relief: Erosion Erosion is the gradual wearing away (destruction and /or removal) of land surface material, for example rock or soil. Three step process: – Weathering of rock (destruction of rock) – Transportation of soil and rock debris (through water, wind, glaciers). – Deposition of material at another location

22. View from the mountain:

23. Montréal

25. Effects of erosion Hole on Sherbrooke May 2012 Caused by hole in water collecting pipe What happened?

26. homework Worksheet to be collected next class

27. Categories of Weathering / Erosion Mechanical Weathering – Composition of rock does not change – Through: - Variations in temperature and pressure  example: freeze thaw cycle of water - Wind and water Chemical Weathering – Composition of rock changes – Through: - washing out of certain minerals  enhanced through acid rain Biological Weathering – Living organisms release acids  change + weaken the rock – Plant roots can break rocks.