1. Weathering

2. Has your family’s car ever hit a pothole?
What causes potholes?

3. Why does every thing look broken up?

4. What is weathering?
Weathering is the chemical and physical breakdown of rocks into smaller fragments.
An end product of weathering is called soil.

5. There are 2 main different types of weathering
There are 2 main different types of weathering. Today we will talk about:
Physical (Mechanical) Weathering - the process that causes rocks to split or break into smaller pieces with NO CHANGE in composition.

6. Abrasion (scratching) by other rocks.
*Common Weathering agents:
Biological activity.
Ice and water
Abrasion (scratching) by other rocks.

7. Types of Physical Weathering
Frost Action: breakup of rock caused by the alternate freezing and melting of water.

8. How does this happen? Water seeps into small cracks in rocks
When the water freezes it expands creating great pressure
The crack widens and allows water to seep deeper into the rock

9. Frost Action
Ice Freezing in cracks in rocks

10. Result after ice melts

11. Frost Action is the most common type of Physical Weathering in NYS. WHY?
The climate of NYS allows for alternate freezing and melting temperatures in our winter months.

12. A) dry and hot B) dry and cold C) moist and hot D) moist and cold
1.In which climate does physical weathering by frost action most easily occur?
A) dry and hot
B) dry and cold
C) moist and hot
D) moist and cold

13. Abrasion – wearing down of rocks as they rub against each other.
This causes rocks to get smoother and rounder

14. Abrasion

15. Harder rocks are more resistant to weathering
*Harder rocks are more resistant to weathering! *Softer rocks are less resistant to weathering!

16. These rocks were carved out by wind-blown sand
These rocks were carved out by wind-blown sand! (like rubbing sandpaper)

17. Quartz is very hard to abrade because of its hardness (7 on the Moh’s scale)

18. Softer rocks are easier to abrade (scratch)
EX. LIMESTONE IS RELATIVELY SOFT, SO IT
WEATHERS RELATIVELY EASILY.

19. Which rock layer is the most resistant to weathering?
b. 2
c. 3
d. 4

20. Exfoliation – peeling of surface layers
rock is repeatedly subjected to heat and cold
outer layer expands in heat and contracts in cold
over time this causes the outer layer of rock to peel off 

21. Examples of Exfoliation

22. Plant (Root) Action – Plant roots grow into cracks of rocks, eventually causing them to split and crumble

23. In the pictures above tree roots can be seen growing directly on rocks
In the pictures above tree roots can be seen growing directly on rocks. In the picture to the right, the rock has been broken in two by the force.
(Harriman State Park 2005)