1. Forces That Shape Our Earth:
Weathering
And
Erosion

2. Weathering & Erosion:
Erosion and weathering are major forces that shape Earth’s surface.
For example, the Grand Canyon was formed through erosion by the Colorado River running through it.

5. What is weathering?
Weathering is the breaking down of rocks and earth materials into smaller pieces called sediment.
There are two types of weathering:
1. Mechanical /Physical
2. Chemical

6. So what is erosion?
Erosion:
The movement
of weathered
rock by wind, water, glaciers, and gravity.

8. Types of Weathering: Mechanical or Physical:
Rock is physically broken into smaller pieces (larger pieces become smaller pieces of the same rock)
Chemical:
Rock is chemically changed (like rusting or dissolving away).

9. 5 Ways that Physical Weathering Occurs:
Release of Pressure
Freezing & Thawing
Animal Actions
Plant Growth
Abrasion

10. Release of Pressure
As the surface of a rock is eroded, the rock begins to release pressure.
This pressure causes top layers of the rock to crack and flake off.

11. Release of pressure: (Rock cracks like an egg shell.)

12. Freezing & Thawing
When water in the cracks of rocks freezes, it expands causing the crack to enlarge or get bigger. The ice melts & refreezes over and over, breaking the rock apart.

13. Result of Freezing & Thawing

14. Animal Actions
Animals dig (burrow) through the ground to make their homes.
This digging loosens the soil and breaks the rocks apart.

16. Plant Root Growth
Plants roots can grow into cracks in the rock, slowly breaking them apart.

18. Abrasion
Sand and other rock particles in wind, water or ice can wear away exposed rock surfaces.
It is like using sandblasting or sandpaper on wood.

21. Chemical Weathering
The process that breaks down the surface of rock by chemical changes.

22. 5 Ways that Chemical Weathering Occurs:
Water
Oxygen
Carbon Dioxide
Living Organisms
Acid Rain

23. Water Water dissolves rocks over time.
Water is the most important cause of chemical weathering

25. Oxygen
Oxygen + Water + Iron = Rust through the chemical reaction called oxidation.
Rock will become crumbly, soft, and appear reddish-brown in color.

26. Rusted rock on hillside

27. Carbon Dioxide CO2 + rainwater = Carbonic Acid
Carbonic acid weathers softer rock like limestone & marble as it seeps into spaces in rock.
Examples: sinkholes and caves.

29. Living Organisms
The roots of plants make a weak acid that slowly dissolves rocks around the plant.

30. Lichens grow on rock

31. Acid Rain Acid rain causes rocks to weather very rapidly.
Acid rain is more common around volcanic areas.