1. Find and photograph 6 examples
of weathering and erosion.

2. Mechanical and Chemical
Weathering
Mechanical
and
Chemical

3. Ecoregion- Ecosystem Weathering Erosion Deposition
Area of land with
identifiable climate,
vegetation
and habitats
Ecosystem
Community of organisms
and their environment
Weathering
Breakdown of rocks into
smaller pieces (sediment)
Process by which wind, water
or gravity move sediment from
One place to another
Erosion
Leaving behind of
sediment by wind, water
or gravity
Deposition

4. What Caused This?

5. What is Weathering? First step to forming soil and sedimentary rock
Breakdown of rock into smaller pieces
The smaller pieces do not move to a new location until erosion carries them away.
Many types of weathering

6. What is Mechanical Weathering?
Physical breakdown of rock into smaller pieces without any change in the chemical composition of its minerals
Sometimes called “physical” weathering
Rock is torn apart by physical force, rather than by chemical breakdown.
Smaller pieces do not move to a new location until erosion carries them away.

7. Mechanical - Ice Wedging
Water fills joints of rocks and freezes.
Water expands 10% when it freezes, pushing rock apart.
Repeated freeze and thaw cycles over the years causes rock to break along joint.

8. Cemetery Field Trip

9. Mechanical (Physical) - Exfoliation
Exfoliation or unloading
-Rock breaks off into
sheets along joints which
are parallel to the surface.
-Caused by expansion of
rock due to uplift and
removal of surface material
that originally buried the rock

10. Mechanical (Physical) - Thermal
Thermal Expansion
Repeated daily heating & cooling of rock
Heat causes expansion
Cooling causes contraction.
Different minerals expand and contract at different rates causing the rock to split.

11. Mechanical (Physical) - Biotic
Biotic – means life
Weathering caused by living organisms
Plant roots act as a wedge and widen cracks.
Other causes of biotic weathering:
burrowing animals
microscopic plants
animals
algae
fungi

12. What is Chemical Weathering?
Chemical reactions break down bonds holding the rocks together, this breakdown causes them to fall apart.
Chemical weathering occurs in all types of rock.
Rock reacts with water, gases and solutions

13. Chemical - Oxidation
Oxidation - oxygen combines with other elements in rocks to form new types of rock
New substances due to oxidation:
rock softer than original
easier for other forces to break rock apart
“rusting” of the rock
color change in the
rock

14. Chemical - Carbonation
Carbonation – Carbon dioxide (CO2) is dissolved in water making carbonic acid
ACIDS
Weak acid is formed when CO2 in the air mixes with rain.
Acid is too weak to harm plants and animals but slowly causes feldspars and limestone to decompose.

15. CO2 + rainwater = Carbonic Acid
Carbon Dioxide
CO2 + rainwater = Carbonic Acid
*Carbonic Acid weathers softer rock like limestone & marble as it seeps into spaces in rock.
*Acid rain causes rocks
to weather very
rapidly.

16. http://www. smithsonianmag
Acid Rain?

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

18. Lichens grow on rock