2. Weathering

3. Review Vocabulary acid: solution that contains hydrogen ions Weathering breaks down materials on or near Earth’s surface.

4. I. Mechanical Weathering Mechanical weathering is a type of weathering in which rocks and minerals break down into smaller pieces. Mechanical weathering is a type of weathering in which rocks and minerals break down into smaller pieces. It does not change a rock’s composition. It does not change a rock’s composition.

5. A. Effect of temperature 1.Frost wedging a. Freeze-thaw cycle of water b. Water expands 9% 2. Breaks rock into smaller pieces

6. 1.Small scale a. Plant or tree roots wedged in the cracks of rocks b. Grow and expand, which often causes the rocks to split. B. Effect of pressure

7. 2. larger scale a. overlying rock layers removed by erosion or even mining b. pressure on the bedrock is reduced c. bedrock surface that was buried expands d. long, curved cracks form (AKA joints)

8. 3. Exfoliation a. outer rock layers are stripped away b. resulting in dome-shaped formations

9. II. Chemical Weathering A. rocks and minerals undergo changesin their composition 1. Agents a. water b. oxygen c. carbon dioxide d. acid precipitation

10. 2. Results a.Dissolving Rock b.Formation of new minerals ex: 4Fe + 3O 2 2Fe 2 O 3 Iron Oxide (hematite) Iron Oxide (hematite)

11. The composition of a rock determines the effects that chemical weathering will have on it. Temperature is a significant factor in chemical weathering because it influences the rate at which chemical reactions occur.

12. 3. Composition a.Calcite will decompose completely in acid ex: Limestone & Marble

13. 4. Temperature a. As temp. Chem. Reaction b. Doubles every 10 o C increase

14. 1.Universal solvent 2.Serves as a medium 3.React directly with minerals in a chemical reaction a. Breakdown large molecules ex: Potassium feldspar kaolinite (fine-grained clay) (fine-grained clay) B. Effect of water

15. 1. Iron in rocks and minerals combines with atmospheric oxygen to form minerals with the oxidized form of iron. Hematite is a common example. C. Effect of oxygen (Oxidation) Hawaii

16. 1.Combines with water in atmosphere/ground 2.Forms carbonic acid a. Acid precipitation b. Dissolve certain rocks, such as limestone 3. Decaying organic matter adds CO 2 to soil a. Limestone caverns D. Effect of carbon dioxide

17. 1. Burning fossil fuels a. Sulfur dioxide a. Sulfur dioxide b. Carbon dioxide c. Nitrogen oxides 2. Dissolves rocks 3. Harmful to plants and animals E. Effect of acid precipitation

18. III. Rate of Weathering The natural weathering of Earth materials occurs slowly. However, certain conditions and interactions can accelerate or slow the weathering process. Valley of the Moon: San Juan, Argentina

19. A. Effects of climate on weathering 1. Chemical weathering a. Rapid in high temperatures b. Abundant rainfall c. Lush vegetation 2. Physical weathering a. Rapid in coolclimates

20. Cleopatra’s Needle (NY, NY)Pylon of Ramses (Egypt)

21. Limestone vs. granite B. Rock type and composition

22. Mechanical weathering breaks rocks into smaller pieces. As the pieces get smaller, their surface area increases, resulting in more total surface area available for chemical weathering. C. Surface area

24. 1.Steep slopes promote erosion 2.Continually expose less-weathered material 3.Gravity D. Topography

25. What effects do mechanical and chemical weathering have on the rock at Earth’s surface?

26. Answer: Mechanical weathering breaks rock apart but does not change its composition. Chemical weathering dissolves some rock and also causes some new minerals, such as iron oxides and clays, to form.