1. Weathering and Erosion Mr. Scichilone

2. Weathering
Weathering is simply the chemical and/or physical breakdown of a rock material--weathering involves specific processes acting on rock materials at or near the surface of the Earth

3. Types of Weathering Physical Weathering( mechanical)
Takes place when rock is split or broken into smaller pieces of the same material without changing its composition.
Example: Breaking of a rock cliff into boulders and pebbles

4. Physical Weathering
Process by which rocks are broken down into smaller pieces by external conditions.
Types of Physical weathering
Frost heaving and Frost wedging
Plant roots
Friction and impact
Burrowing of animals
Temperature changes

5. Frost Wedging

6. Plant Roots

7. Temperature Changes

8. 3. Temperature Changes · Climate: Hot and Arid (dry)
1. Objects expand and contracted when heated and
cooled
2. When rocks are heated and cooled cracks
are created.
3. Overtime rocks are weathered
· Agent: Temperature
· Climate: Hot and
Arid (dry)

9. 4. Abrasion · Agents: ice, gravity, water, air
·When rocks grind against other rocks.
·Over time they get smaller
· Agents: ice, gravity,
water, air
· Climate: All Climates

10. Plant Action—growing roots weaken the rocks
Plant Action—growing roots weaken the rocks. Water pressure in the roots cracks rocks
Animal Activity—holes and burrows dug by animals lets air and water into the ground
Abrasion—”sand blasting” of rock by wind or water.

11. Types of Mechanical Weathering
Action of plants and animals:
Lichens and mosses grow on rocks
They wedge their tiny roots into spores and crevices.
When the roots grow, the rock splits.
Action of plants and animals:
Lichens and mosses grow on rocks
They wedge their tiny roots into spores and crevices.
When the roots grow, the rock splits.
Action of plants and animals:
Lichens and mosses grow on rocks
They wedge their tiny roots into spores and crevices.
When the roots grow, the rock splits.

12. Types of Mechanical Weathering

13. Types of Mechanical Weathering
Frost Action—freezing of water in a joint, the water/ice expands widening the joint. The ice melts and water seeps deeper and the process repeats
Exfoliation—peeling off of large curved sheets of rock from an exposed surface
Usually need a release of pressure
Temperature changes can speed this process

14. Exfoliation Forest fire in Glacier National Park (taken 8/2008)

15. Exfoliation Forest fire in Glacier National Park (taken 8/2008)

16. Exfoliation Forest fire in Glacier National Park (taken 8/2008)

17. Chemical Weathering
The process that breaks down rock through chemical changes.
The agents of chemical weathering
Water
Oxygen
Carbon dioxide
Living organisms
Acid rain

18. Water
Water weathers rock by dissolving it

19. Oxygen
Iron combines with oxygen in the presence of water in a processes called oxidation
The product of oxidation is rust

20. Carbon Dioxide CO2 dissolves in rain water and creates carbonic acid
Carbonic acid easily weathers limestone and marble

21. Living Organisms
Lichens that grow on rocks produce weak acids that chemically weather rock

22. Acid Rain
Compounds from burning coal, oil and gas react chemically with water forming acids.
Acid rain causes very rapid chemical weathering

23. Factors that Affect the Rate of Weathering
·Exposure
·Particle Size
·Mineral composition
·Climate

24. Particle Size
·The smaller the particle the faster the rate of weathering will be.
·An object that is crushed has larger surface area and therefore will weather faster.
Checkpoint:
Which would weather faster?
AN ENTIRE MOUNTAIN A BOULDER THE
SIZE OF A CAR

25. Surface Area Animation

26. 3. Which tablet dissolved the fastest?
Surface Area Rate of Weathering Activity
Whole Tablet Crush Tablet
Questions:
1. Both tablets have the same mass, which tablet has a larger surface area?
2. Predict which tablet will dissolve fastest in beakers of water with the same temperature.
3. Which tablet dissolved the fastest?
4. Discuss with your partners and explain why the results turned out as they did.
*Be prepared to share your results with the class upon return to seats

27. Mineral composition Question: Which type a rock would weather faster?
·Different minerals have different properties.
·Some minerals dissolve faster in water than
others.
·Hardness also can determine rate of
weathering.
Question:
Which type a rock would weather faster?
Hard Rock Soft Rock
Soft Rock

28. Checkpoint #1 1
Which type of climate has the greatest amount of rock weathering caused by frost action? A
a dry climate in which temperatures remain below freezing B
a dry climate in which temperatures alternate from below freezing to above freezing C
a wet climate in which temperatures remain below freezing D
a wet climate in which temperatures alternate from below freezing to above freezing.

29. Checkpoint #2 2
The diagram shows the stump of a tree whose root grew into a small crack in bedrock and split the rock apart.
The action of the root splitting the bedrock is an example of A
Chemical Weathering C
Erosion B
Deposition D
Physical Weathering

30. Checkpoint #4 4
The picture (see image) shows a geological feature in the Kalahari Desert of southwestern Africa. Which process most likely produced the present appearance of this feature? A
Wind Erosion C
Earthquake Vibrations B
Volcanic Eruption D
Plate Tectonics

31. Checkpoint #6 6
Which climatic conditions normally produce the greatest amount of chemical weathering? A
cool and dry B
cool and moist C
warm and dry D
warm and moist

32. Checkpoint #9 9
Which will weather the fastest? Why? A C B D