1. There are 2 primary forces that shape our landscape:
1. Weathering and Erosion (destructive) –wears the land down
2. Mountain Building (constructive) –builds the land up
When these 2 opposite forces actively equal one another, the
area affected is in dynamic equilibrium

2. weathering
Weathering is the breakdown
of rock (the earth’s crust) by either
physical or chemical means

3. Physical Weathering 1) Freeze-Thaw or Frost Wedging 2) Exfoliation
3) Biological or Root Action

5. Freeze-thaw

7. Talus slope

8. Frost heaves form
by the same process

9. Biological weathering
What has caused the cracks to appear?

10. Plant action

11. The tree roots
are breaking up
the curb stone

12. Exfoliation or onion-skin weathering
During the day the sun heats up the surface of the rock causing the rock to expand.
During the night the rock cools down and contracts.
As the rock expands and contracts over and over again, small pieces of surface rock begin to flake and fall off.
Onion-skin weathering is a form of physical weathering.

13. Exfoliation dome

14. Exfoliation on
this boulder
Like peeling the
layers off an
onion

15. How do you think these rocks have become weathered?
Chemical weathering
How do you think these rocks have become weathered?

16. Chemical weathering
Plant action

17. Hieroglyphics almost gone
due to humid climate
in NYC
hieroglyphics as they
appeared in Egypt

18. Chemical weathering occurs fastest in
tropical climates (hot and humid)
because high temperatures and water both
speed up chemical reactions

19. Frost action occurs
best in cold mountain
climates

20. exfoliation works best
In highland or dry climates

21. exfoliation dome in
Yosemite National Park

22. Chemical weathering from salt
water in waves pounding this
cliff

23. The final product of weathered rock is sand or
soil, depending on available organic material

24. 100 years ago
7 years ago
35 years ago
present
What happens to the rate at which rock weathers as
It breaks into smaller pieces?

25. Why would a rock weather faster as it breaks into More pieces?
Answer: more surface area becomes exposed to atmosphere

26. very hard rock Soils that develop from the rock directly underneath
are called residual soils
very hard rock
Soft rock
Which rock will develop top soil fastest?
the average rock takes 100 years to develop 1 inch
of top soil

27. As rock weathers 4 horizons of soil develop “A” horizon topsoil
(w/ humus, organics,
biological activity)
“B” horizon
subsoil
“C” horizon
Partly weathered bedrock
“D” horizon
Unweathered bedrock

28. Types of soil Residual soils form in place by weathering
Transported soils are brought from other areas, usually by glaciers
Most soils in NY are TRANSPORTED