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FINAL EXAM REVIEW
Part 1-- Weathering, Erosion, Mass Wasting
Weathering – breaking rocks down into smaller and smaller
particles. The particles stay in place - not moved by wind water or
ice
Erosion =removal of rock particles and soils by water, wind or glacial ice.
Transportation of particles is part of the erosion process
(Weathering weakens the rocks, while erosion moves the weathered material.)
Mass Wasting – movement of rock and soil downward due to
gravity.
These processes are an important part of the rock cyclecreating sediment that may become sedimentary rocks or soil
By studying the effects of weathering- we can make stronger
roads, and structures that last longer without costly repairs
Types of weathering
1. Mechanical Weathering:
Physically breaking of rocks by abrasion,
impact, etc.
2.Chemical Weathering
Decomposition of rock from exposure to
atmospheric gases (oxygen, water vapor and
carbon dioxide) or liquid water= a chemical
reaction takes place
Types of Mechanical Weathering
1. Frost Wedging
Cold weather needed to
freeze the water
Water fills
the cracks in
the rocks
Water expands
when it freezes
causing the crack to
widen
Rocks finally
split/ break
apart
Types of Mechanical Weathering
2.Thermal Cycling
Large temperature variations break rocks with
due to repeated expansion and contraction
3.Pressure Release or Exfolitaion
Removal of overlying rock layers, releases
pressure,
Underlying rocky material is pushed upward
and breaks in sheets
Types of Mechanical Weathering
Plant Growth or Root Wedging
Burrowing Animals
Growing roots widen fractures
in rock
Mr. Gopher likes to move pieces of
rock out of his way- causing rocks
to chip or break
Root wedging
Chemical Weathering
1.Acid Rainwhen water vapor
reacts with CO2,
Sulfur Dioxides ,etc
to produce weak
acids that fall as
rain- dissolving
rocky materialsome rocks
dissolve easier
than othersEx: Limestone
Statues affected by
acid rain
2.Oxidation- reaction of Oxygen
on a substance –ex: rust, tarnish
Close view of the right hand of the Statue of Liberty
Plants can cause chemical weathering
Plant roots can emit chemicals
that dissolve rocks and brick
mortar
Differential Weathering and Erosionsome rocks weather and erode faster
than others
Mass Wasting
Factors making mass wasting likely:
Over steeping or Undercutting
Wave action or Human impact
Thick layer(s) of loose rock , debris, soil
Presence of water
Lubricates moving rocks/debris/soil
Lack of vegetation
No roots to hold rock/soil in place
Seismic (earthquake) activity
Creep (or soil creep)
Very slow down slope movement of soil
Can be costly to maintain homes, etc., on creeping ground as
foundations, walls, pipes and driveways crack and shift down slope
over time
Don’t usually see the movement, just the effects of the
movement
Not straight and upright
Examples of Creep
Curved tree trunks indicate creep
Flow
Fall
A disaster waiting to
happen-Why???
Ways to control Mass WastingBuild a retaining wall
Build a covered Bridge
Stitching
Soil Horizons (Layers)
Dust Bowl- Lasted 10 years- Soil
Conservation Began
Soil Conservation Techniques
Terracing
Contour plowing
windbreaks
Windbreaks
Weathering and Erosion - Recap
A. Weathering=Rocks are broken down into sediments- by Physical or
Chemical means
B. Erosion= The movement of rocky material and sediment by wind ,water
and ice
C. mass Wasting= downward movement of materials due to gravity
I Types of Weathering
A. Mechanical
1. Frost wedging
2. Thermal Cycling
3. Root wedging
4. Pressure release or Exfoliation
5. Burrowing Animals
B Chemical
1 Acid Rain
a. Carbonic Acid
b. Sulfur Dioxides
2. Oxidation
C. DIFFERENTIAL WEATHERING= different types of rocks weather at
different rates
D. Dust Bowl -1930's--- 5 most effected states= Texas, Kansas, Oklahoma,
Colorado, New Mexico ---- Soil Conservation measures were developed due
to the loss of top soil
E. Top soil is the O Horizon (organic material) and the A Horizon(organic and
mineral material) (different layers of soil are called Horizons )
RecapMass wasting is downward movement of materials due to gravity
Types of Mass Wasting
1. Flow
2. Fall
3. Slide
Triggers (something that makes the materials start the downward movement)
1. Saturation- too much water
2. Lack of vegetation
3. Over steeping
4. Undercutting
5. Earthquakes
6. Adding additional weight such as a house or building
Slowest type of Mass Wasting is Creep
Prevention – Ways to reduce or slow the amount of Mass Wasting
1.Retention Walls- must have drainage
2. Stitching rocks together with bolts
3. Build a covered area so rocky material will not fall on a roadway
4. Removal of loose materials
5.Removal(if possible) of the over steeped area
6. Terracing - used on hill sides