1. This week we write it down if it’s in ORANGE.
Weathering
This week we write it down if it’s in ORANGE.
Photo: Grand Canyon, National Park Service

2. What do you think made the hole in this rock?
Wind blows sand and other sediment against rocks. Little by little, it wears away the rock!
This is an example of mechanical weathering.
What do you think made the hole in this rock?

3. What do you think made the notch where the waterfall starts?
Water from the river wears away the rock, over thousands of years.
This is another example of weathering.
Photo: Yosemite Falls, National Park Service webcam
What do you think made the notch where the waterfall starts?

4. Weathering is the process that breaks down rock and other substances on Earth’s surface.

5. Part 1: Mechanical Weathering

6. Mechanical Weathering
Force of Mechanical Weathering
How it Works
Abrasion
Plant Growth
Animal Actions
Freezing and Thawing
Release of Pressure

7. Here we go again with wind and rock particles sculpting rock!
Photo: Delicate Arch, Arches National Park, National Park Service.
Abrasion: Sand and other rock particles carried by wind and water grind away rock like sandpaper on wood.

8. Perhaps you have seen this on sidewalks?
Photo source: Morguefile.com
Plant Growth: Roots of trees and other plants grow in the cracks of rocks and pry them apart.

9. Photo source: Morguefile.com
Animal Actions: Animals dig in the soil and loosen and break apart rocks.

10. Perhaps you have seen a frozen bottle get cracked
Perhaps you have seen a frozen bottle get cracked? Or cracks in the road? Why does that happen?
Ice Wedging: When water freezes it expands. Ice in the crack of a rock expands and makes the crack larger.

11. Whiteboard Question CHECK YOUR UNDERSTANDING!
Mechanical weathering in which rock is worn away by the grinding action of other rock particles is called
erosion.
abrasion.
ice wedging.
B. abrasion

12. Release of Pressure: When rocks reach Earth’s surface, reduced pressure can cause cracks and flakes in the rock.

13. Mechanical Weathering
Your completed chart should look like this!
Force of Mechanical Weathering
How it Works
Abrasion
Sand and other rock particles carried by wind and water grind away rock like sandpaper on wood.
Plant Growth
Roots of trees and other plants grow in the cracks of rocks and pry them apart.
Animal Actions
Animals dig in the soil and loosen and break apart rocks.
Freezing and Thawing
When water freezes it expands. Ice in the crack of a rock expands and makes the crack larger.
Release of Pressure
When rocks reach Earth’s surface, reduced pressure can cause cracks and flakes in the rock.

14. Whiteboard Question CHECK YOUR UNDERSTANDING!
Ice wedging causes mechanical weathering of rock by means of:
plant growth.
animal actions.
freezing and thawing of water.
C. freezing and thawing of water

15. Chemical Weathering
Write it down if it’s in ORANGE.

16. Chemical weathering is the process that slowly breaks down rock with chemical changes, including changes in the minerals.
This rusty color is caused by
oxidation in a wet climate.

17. Whiteboard Question CHECK YOUR UNDERSTANDING!
What kind of weathering causes the mineral composition of rocks to change?
Chemical weathering.
Mechanical weathering.
General weathering.
A. Chemical weathering

18. Part 2: Chemical Weathering

19. Chemical Weathering Chemical weathering is____________________________________________ _______________________________________________________________
Force of Chemical Weathering
How it Works
Water
Oxygen
Carbon Dioxide
Living Organisms
Acid Rain

20. This limestone cave was created by water dissolving the stone.
Photo source: Morguefile.com
Water: Water is the most important cause of chemical weathering. When a rock dissolves in water, it mixes completely with the water.

21. What made this old truck rusty?
Photo source: Morguefile.com

22. Photo source: Morguefile.com
Rust happens to old vehicles, and to rocks.
Photo source: Morguefile.com
Oxygen: Iron combines with oxygen and water in a process called oxidation. The result is rust. Oxidation of a rock makes it soft, crumbly and red or brown.

23. Limestone.
Carbon dioxide: Carbon dioxide in the air dissolves in rainwater, becoming a weak acid called carbolic acid. Acids weather rocks such as limestone and marble.

24. Lichen growing on a rock will weather it.
Photo source: Morguefile.com
Living organisms: Plants, and other living organisms such as lichen, release weak acids that slowly dissolve rocks.

25. Acid rain: Burning coal, oil, and gas for energy produces pollution
Acid rain: Burning coal, oil, and gas for energy produces pollution. This pollution combines with air and water, to create acid rain, and fast chemical weathering.
Photo source: Morguefile.com

26. Whiteboard Question CHECK YOUR UNDERSTANDING!
A rock containing iron becomes soft and crumbly and reddish-brown in color. It probably has been weathered by:
abrasion
oxygen.
acid rain.
B. oxygen

27. Chemical Weathering Chemical weathering is____________________________________________ _______________________________________________________________
Your completed chart should look like this!
Force of Chemical Weathering
How it Works
Water
Water is the most important cause of chemical weathering. When a rock dissolves in water, it mixes completely with the water.
Oxygen
A rock containing iron becomes soft and crumbly and reddish-brown in color. It probably has been weathered by
Carbon Dioxide
Carbon dioxide in the air dissolves in rainwater, becoming a weak acid called carbolic acid. Acids weather rocks such as limestone and marble.
Living Organisms
Plants, and other living organisms such as lichen, release weak acids that slowly dissolve rocks.
Acid Rain
Burning coal, oil, and gas for energy produces pollution. This pollution combines with air and water, to create acid rain, and fast chemical weathering.

28. Is it Chemical or Mechanical Weathering? Final Whiteboard Questions
Abrasion of a rock by blowing sand is an example of __________________ weathering.
Acid rain washing away the face of a statue is an example of __________________ weathering.
True or False? Living things can cause both chemical and mechanical weathering.
A tree’s roots growing through cracks in a rock is an example of _________________ weathering.
chemical
True
mechanical

29. Part 3: Rates of Weathering
What makes a rock weather fastest?
Photo source: Morguefile.com

30. Rate of Weathering
The most important factors for the rate (speed) of weathering are 1. rock type; and 2. climate.
Photo source: Morguefile.com

31. Mechanical and Chemical Weathering Work Together
Photo source: Morguefile.com
Photo source: Morguefile.com
Mechanical weathering increases the surface area available for chemical weathering. Increased surface area usually results in faster chemical reactions (chemical weathering).

32. Mechanical and Chemical Weathering Work Together
Which rock do you think will weather faster?
A permeable rock weathers easily because it contains many small, connected air spaces

33. Whiteboard Question CHECK YOUR UNDERSTANDING!
A permeable rock weathers easily because it:
is made up of small particles.
contains many small, connected air spaces.
is made up of many minerals.
B. contains many small, connected air spaces.

34. How Does Weather Affect Weathering?
Photo source: Morguefile.com
Which of these places would have faster weathering of rock?
Why?
Photo source: Morguefile.com
Photo source: Morguefile.com

35. Rainforests have warm, wet weather.
Photo source: Morguefile.com
Wet climates with high temperatures speed up both mechanical and chemical weathering.
Photo source: Morguefile.com

36. Whiteboard Question CHECK YOUR UNDERSTANDING!
Granite lasts a long time when it is used for building in areas where the climate:
is cool.
has lots of acid rain.
is hot and rainy.
A. is cool

37. Whiteboard Question CHECK YOUR UNDERSTANDING!
The most important factors in determining the rate of weathering are:
carbon dioxide and acid rain.
animal actions and oxygen.
rock type and climate.
abrasion and acids from root plants.
C. rock type and climate