1. Bell Ringer
What processes form igneous rocks? Sedimentary? Metamorphic?
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2. Weathering

3. Weathering Sediment – small pieces of broken-down rock
Sediment is created through the processes of weathering, erosion, and deposition

4. E W D Weathering Weathering – when rocks break down and change
Erosion – the transport of weathered material from one location to another
Deposition – when the erosion movement slows down and drops the weathered material E W D

5. Weathering
Weathering, erosion, and deposition have been happening for millions of years, constantly changing Earth’s surface

6. Weathering
Since weathering constantly wears away at rocks, the more a rock has been weathered, the smoother and rounder it will be

7. Weathering
Two types of weathering:
Mechanical (Physical)
Chemical

8. Mechanical Weathering
Mechanical Weathering -- breaks down rocks into smaller pieces
Changes the physical appearance of the rock (size and shape)
Occurs mostly in cool and dry climates

9. Mechanical Weathering Agents
Freezing temperatures can cause mechanical weathering
Frost wedging – when water in rock cracks freezes and expands, making the rocks crack open or break

10. Mechanical Weathering Agents
Tree and Plant Roots – wedge into cracks of rocks and cause them to split

11. Chemical Weathering
Chemical weathering – breaks down rocks into new substances through chemical reactions
Changes the rock’s chemical composition
Occurs mostly in warm and wet climates

12. Chemical Weathering Agents
Hydrolysis – the chemical reaction of water with other substances
Water dissolves many minerals in rocks

13. Chemical Weathering Agents
Oxidation – the chemical reaction of oxygen with other substances
Example: the oxidation of iron produces rust

14. Chemical Weathering Agents
Carbon dioxide turns into carbonic acid when it mixes with water
Carbonic acid dissolves calcite, a mineral found in limestone, which can create caves where the rock has been eaten away

15. Mechanical or Chemical?
Tree roots start to break apart the nearby sidewalk.

16. Mechanical or Chemical?
Acid rain eats away at marble statues.

17. Mechanical or Chemical?
The Statue of Liberty used to be copper-colored, but extended exposure to oxygen has turned it green.

18. Mechanical or Chemical?
Ocean waves pound against the cliffs, wearing the rocks away.

19. Factors that Affect Weathering
Climate
Mechanical weathering occurs mostly cool and dry climates
Chemical weathering occurs mostly in warm and wet climates
Grand Canyon – mostly mechanical or chemical weathering?

20. Factors that Affect Weathering
Rock Type and Composition
Sedimentary rocks are more likely to weather than igneous or metamorphic rocks
Why might that be?
Igneous and metamorphic rocks are forged together by high heat and pressure
Meanwhile, sedimentary rocks are loosely layered and cemented together

21. Factors that Affect Weathering
Surface Area – how much of the rock is exposed to wind and water
As a rock breaks down into smaller and smaller pieces, the MORE surface area it has
The more area exposed, the more weathering can take place
As rocks are broken down into smaller and smaller pieces, their surface area (SA) and rate of weathering increase.
(low SA) (high SA)

22. What dissolves faster?
Sugar Cubes
Granulated Sugar or

23. Factors that Affect Weathering
Topography – materials on sloped surfaces are more likely to weather and erode due to gravity

25. WED Analysis