Lesson 1 in Earth and Life Science - Weathering

Weathering is the natural process that breaks down rocks, soil, and minerals into smaller pieces over time due to exposure to the atmosphere, water, and living organisms

1. Objective Describe how rocks undergo weathering

2. what is weathering?

3. Weathering- is a natural process by which rocks, soil, and minerals are broken down into smaller pieces by physical, chemical, or biological forces

4. TYPES OF WEATHERING 1. Physical weathering - rocks disintegrate or break up into smaller pieces - happens when there are changes in temperature over a short period of time two types of physical weathering are: freeze-thaw weathering and exfoliation

5. a. Freeze-thaw weathering - occurs when rocks are porous (has holes) or permeable (allow water to pass through), water seeps into cracks, freezes and expands and eventually breaking the rock apart

6. Freeze-thaw

7. b. Exfoliation- occurs when the outer layers of rocks fracture off

8. This happens when… rocks  are  heated  and  expand  in the heat  of the  day   and then  cool  and  contract  in the  cold  of the  night The  expansion  and  contraction  makes  thin slithers  of  rock tend to  flake off  the  surface , and these  flakes  can then be broken further  into  tiny pieces - exfoliation  can also be referred to as  flaking

9. Agents of physical weathering : 1. water 3. gravity 5. ice 2. wind 4. plants 6.temperature (heat & cold)

10. 2. Chemical weathering - rocks decompose due to changes in its chemical composition -caused by chemical reactions between minerals in rocks and environmental agents like water, acids, and gases - dead plants can also cause chemical weathering by producing acids when they rot Water - is an important agent of chemical weathering

11. types of chemical weathering A. carbonation- occurs when water mix with carbon dioxide to make carbonic acid which reacts with minerals in rocks B. Oxidation- occurs when oxygen combines with another substance and create compounds like oxides (ex. Rust or iron oxide) - when rust expands, it weakens rock and helps break it apart

12. 3. Biological weathering - is caused by the movements of plants and animals - the roots of plants grow down through soil and rocks to find water and minerals - rocks break up due to the roots of the plants that grow on the cracks which made it wider and eventually cause the rock to disintegrate

13. - a rabbit can burrow into a crack in a rock making it bigger and eventually splitting the rock

14. The speed at which rock weathering occurs is dependent on: 1. type and hardness of minerals in the rocks 2. type of rock 3. climate Some rocks react with water, others react with acids Sedimentary rocks weather fastest Rocks weather faster in areas that are humid and with high precipitation

15. Two major effects of weathering 1. soil erosion 2. landslide

16. Why is weathering important? - weathering is a crucial part of the rock cycLe - it breaks down rocks and minerals, which helps create soil Weathering also helps develop landforms such as canyons, plateaus, mountains and valleys

17. reflection What do you think will happen if rocks will not undergo weathering?

18. Lack of Soil Formation Disrupted Rock Cycle Altered Landscape Impact on Ecosystems

19. Activity 1 Directions : Study the diagrams below and answer the following: 1. Which of the flow diagrams below illustrate physical weathering, chemical weathering and biological weathering? State your reason on the space provided. Fig. 1. WEATHERING PROCESS A

20. Fig. 2. WEATHERING PROCESS B Fig. 3. WEATHERING PROCESS C

21. R reasons: A._________________________________________________________________ B._________________________________________________________________ C._________________________________________________________________ D._________________________________________________________________ Fig. 4. WEATHERING PROCESS D

22. Answer the following questions: 1. What takes place during weathering? ____________________________________________ 2. How would you differentiate the three types of weathering? ____________________________________________

23. Thank you for listening