1. Breaking it Down
Weathering & Erosion

2. Do Now
5 minutes
Breaking it Down Key Question: What is weathering, and what are some examples? Initial Thoughts:

3. Evidence: Weathering
Large rocks and landforms first need to be broken down into smaller pieces in order to be worn away by erosion.
This is accomplished by weathering - the breaking down of rock by chemical or mechanical processes

4. Mechanical Weathering
Definition: Breaking up of rock by physical forces, such as the action of wind and moving water.
The rock itself does not change; it just gets broken into smaller pieces.
Process Name
Where does it occur?
What is it?
Break an Alka-Seltzer tablet with a hammer

5. Go to the website, which can be found on my links page under “Mechanical Weathering, and click “NEXT” twice:

7. Exfoliation or unloading -
rock breaks off into leaves or sheets along joints which parallel the ground surface;
caused by expansion of rock due to uplift and erosion; removal of pressure of deep burial

8. Organic activity (TREES/root-pry, burrowing animals, human activities)

9. Abrasion & Gravity: rocks falling and colliding with other rocks

10. Contraction due to crystallization
The surface pattern on this pedestal rock is honeycomb weathering, caused by salt crystallization. This example is at Yehliu, Taiwan.
Salt weathering of building stone on the island of Gozo, Malta

11. Chemical Weathering
Definition: wearing away of rocks by chemical processes, such as dissolving or oxidation. (in your journal vocab)
It’s a breaking down process

12. Dissolving Acids or water dissolve the rocks.
Sources: Acid rain from pollution, plant roots, water & limestone (example caves),
Water: Dissolves minerals out of rocks making them weaker

13. Chemical weathering
Acid: Dissolves minerals in rocks examples: carbonic acid, acid rain, and plant acid

14. Lichens such as these growing on the rocks in the picture can produce weak acids that react with the rock.

16. 3000 year old Egyptian Obelisk after 100 years in NY

17. Oxidation
Oxidation or rusting - some minerals contain metals, like Iron or sulphur, that can rust when exposed to oxygen. Just like an old car, nail, or piece of metal left outside.

18. Oxidation

19. Evidence 2: Weathering Lab
Each group will be assigned one of the 4 treatment groups:
Crushed tablet vs. Whole tablet
Heated water vs. room-temp water
Vinegar vs. water
Heated vinegar vs. room temp vinegar

20. Make a hypothesis
If we test (treatment group) then the time it takes for the tablet to completely dissolve will be faster/slower.
Use 150 ml of liquid
Record the time it takes for the tablet to dissolve

21. Class Data Recreate this table in your journal
Treatment Group
Average time in minutes:seconds to dissolve
Crushed tablet vs. Whole tablet
Heated water vs. room-temp water
Ice cold water vs. room temp water
Vinegar vs. water

22. Analysis Q’s
Compare & contrast mechanical and chemical weathering. (a venn diagram or chart is o.k.)
A) Which of the treatment groups in the lab represented mechanical weathering? B) Which were chemical weathering?
Why do you think the obelisk (slide 17) showed more weathering during the 100 years in New York than it did in the 3,000 years it was in the desert in Egypt?

23. Summary
What did you think about how weathering works before this lesson?
What did you learn about how weathering works from this lesson? (Minimum of 3 sentences!!!)
What are some further thoughts or questions you have about how weathering works?

24. Reflection
Explain how mechanical and chemical weathering are similar to the process of mechanical & chemical digestion. Use words, pictures, or both.

25. Big Idea
Rock landforms can be broken down by the natural processes of mechanical & chemical weathering.

26. Do Now 4-14-14 New Seats Turn in your Paper Plate Rock Cycle
Update your grades page:
4/1 Rock Cycle
4/3 Vocabulary
Read the Learning Target
4 minutes