1. Chapter 9 Weathering and Erosion
Workbook p

2. Weathering
As long as bedrock stays underground, it will basically remain unchanged
Once a rock outcrop is exposed to the surface, it will go through changes
It will WEATHER
To break down
Two types of weathering:
Chemical and Physical Weathering

3. Chemical vs. Physical Chemical To break down into another form
More common in hot, wet areas
Examples:
Rust, Limestone caves and acid rain, “burning paper”
Physical
To break down into a smaller version of the same form
More common in cool, dry areas
Examples:
Frost Action, Plants, Soil formation “tearing paper”
See p. 96, Figure 4-3

7. Factors that Affect Rate and Type of Weathering
Exposure
Closer to Earth’s surface, the faster it will weather
Longer the time of exposure, the more weathering that will occur
Particle Size
The smaller the pieces, the faster the weathering
Ice block vs Crushed Ice
Mineral Composition
Harder minerals are harder to weather
Climate
Chemical weathering = warm and moist climates
Frost action = moist climate that has a repeating freezing-thawing cycle

8. Soil Formation
Weathered rock, microorganisms, and organic remains (i.e.-poop, dead things)
NOT dirt
Dirt is only weathered rock
Covers bedrock in layers, called horizons
Bedrock is solid layer of rock beneath soil and dirt
Most important layer is the humus
Also called topsoil
Most important layer
Contains THE MOST organic remains
Considered rich
Must be protected
It can take 100’s of years to produce 1cm of topsoil
See p. 185, Figure 9-5

9. Weathering vs. Erosion Weathering To break down
Materials stay where they are
Erosion
To move sediments away
Materials are weathered first, then eroded
Weathered sediments are deposited in a different location
Force of gravity drives most forms of erosion
There are 5 agents of erosion…

10. Open your workbook to p. 186 (1-10)
1 (#2 is erosion, not weathering) 2 4

11. 1- Erosion by Gravity Alone
Also known as mass movement
Avalanche, landslide, slow creep, mudslide
Rocks can fall off of a cliff
Rocks off of a cliff will be smooth on one side and rough on the other
Unsorted rocks

12. 2- Erosion by Wind Occurs in areas with little to no plant life
Causes rocks to be pitted on one side
Sandblasting
Very angular (pointy)
Moves sand dunes from wind side to non-wind side
Up with a slope (wind side)
Down steep (non-wind side)

14. 3- Erosion by Water Rivers erosion is the most common form of erosion
Velocity is caused by 3 things
Discharge amount
Slope
Size of river
ESRT p. _ The bigger the velocity of the water, the larger the particle it can move
Causes V-shaped valleys
riVer

15. Meandering Rivers Rivers slow because of a meander
Water moves fastest on the outside of a bend and slowest on the inside of a bend
Fast = Erosion
Slow = Deposition

17. 4- Erosion by Waves and Current

18. 5- Erosion by Ice Glaciers are slow moving, massive blocks of ice
Glaciers form parallel grooves in the bedrock from dragging things
In between the grooves, the bedrock is polished
Glaciers form U-shaped valleys

19. Other Erosional Facts Erosion by Living Organisms
Living things (humans for example) dig up the Earth and move it all of the time
Humans cause THE MOST amount of erosion in the world
Deforrestation
Animals dig burrows
Plants’ roots break up the ground
Mass Movements
Slides, flows, and falls
Caused by unstable conditions in slope materials