1. Weathering and The Rock Cycle

2. Weathering
Weathering is the breaking down of rocks into sediments. After the rocks have been broken other forces carry the rocks away.
Weathering affects rocks, caves, mountain and even buildings and streets. Different types of weathering (chemical and mechanical) break down earth’s surface and have changed what we see over billions of years. Mountains becomes hills.

3. Mechanical Weathering
Mechanical weathering occurs when rocks are broken apart by physical processes.
The rocks actually disintegrate but the overall chemical make-up of the rock stays the same. Each piece of rock is similar to the original rock. It is like a jackhammer smashing up rock.
Growing plants, burrowing animals, and expanding ice can mechanically weather rocks. Enough force is created to break the rocks into smaller pieces.

4. The Major Types of Mechanical Weathering are:
1.) Frost Wedging
2.) Exfoliation/ Uploading
3.) Organic Activity

5. Mechanical Weathering – Frost Wedging
When water enters the cracks in a rock and freezes, it expands.
The cracks enlarge and the rock breaks apart.
Then more water can enter the crack, freeze and expand, causing the cracks to grow bigger. This processes also breaks up roads

6. Freeze Thaw Cycle

7. Freeze Thaw Cycle

8. Mechanical Weathering - Exfoliation
The rock weathers and erodes away
There is less weight and pressure pushing down on the rock
The rock expands upward under reduced pressure and breaks into sheets and slabs.

10. Mechanical Weathering - Organic
Water and nutrients that collect in the cracks of a rock allow plants to grow.
Plant roots grow into rocks and split it apart
Burrowing animals, such as earthworms and moles can loosen sediments.

12. Mechanical Weathering
Once a rock weathers, its surface area increases, thus the surface area exposed allows for more weathering

13. Chemical Weathering
Chemical Weathering occurs when chemical changes dissolve the minerals in rocks or change the minerals into different minerals.
Occurs when rocks react with air, water and other chemicals.
2 major types of chemical weathering:
Oxidation
Acid reactions

14. Chemical Weathering - Oxidation
When rocks containing iron are exposed to air and water
The rocks oxidize or “rust” producing a red colour
A rusty nail or bike chain

16. Chemical Weathering – Acid Reactions
When water reacts with carbon dioxide it produces carbonic acid.
The acid reacts with the rocks that contain calcite (Limestone)
Rocks like Limestone will dissolve from the acid.

18. Factors affecting Weathering
2 Major factors affecting weathering are:
Mineral Composition of Rock
Some minerals are less stable and dissolve faster than others
Climate of a region
The warmer and more wet a region is, the more weathering occurs
Climate affects both mechanical and chemical weathering

19. Rock Cycle
Rocks can be broken apart, chemically altered, dissolved and carried away by water and ice. Once the rock reaches a new location, it can undergo even more changes and become part of an entirely different family of rocks. Sedimentary rocks can become metamorphic rocks. Metamorphic rocks can become igneous rocks.

20. Rock Cycle
The ROCK CYCLE consists of the processes in which rocks are continually changed over long periods of time.

22. How the Rock Cycle Works
Many foods are made by the same processes that rocks undergo in the rock cycle.
How is chocolate fudge like an igneous rock? (heating and cooling)
How is a granola bar like a sedimentary rock? (different types of sediments cemented together)
How is a grilled cheese sandwich like a metamorphic rock? (how heat transforms the cheese)

23. Bonus Activity
Complete a diagram and write-up with your class a food you could use to represent processes in the rock cycle. Explain the similarities between rocks and your food. Discuss what steps of the food preparation represent processes in the rock cycle.