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WEATHERING

VIEWS: 2 PAGES: 89

  • pg 1
									WEATHERING AND
   EROSION
Rock Cycle
                  WEATHERING
I. Weathering - The breakdown of rock due to exposure to the
atmosphere, weather, plants, and animals.
       A. Mechanical Weathering (Physical Weathering) -
Rock is split or broken into smaller material without changing
its composition.
      B. Chemical Weathering – Process by which rocks
break down as a result of chemical reactions.
Mechanical (Physical)Weathering
 1. Ice wedging (Porus, rocks with cracks (ice
  heaving/Frost Action)
 2. Wetting and drying (for clay containing rocks)
 3. Plants (lichens, mosses, shrubs, trees)
 4. Exfoliation (the peeling away of surface layers)
  due to the relief of pressure from rocks above it.
 5, Expansion / Contraction (Temperature)
 6. Abrasion- process of breaking down by means
  of friction
ABRASION
ABRASION BY WATER
Abrasion – wears down or rounds
ABRASION BY WIND
MECHANICAL WEATHERING
               Was once
               solid rock
MECHANICAL WEATHERING
ICE WEDGING
PLANTS
EXFOLIATION
Exfoliation – causes rock to
sheet or flake off
Barrel cactus – breaking through
rock to grow
EXFOLIATION
                WEATHERING


B. Chemical Weathering - Break down of rocks when
the rock minerals are changed to different substances.
   Chemical Weathering
 1. Hydrolysis - chemical reaction with water and other
  substances (feldspar, hornblende, augite) these combine to
  form clay.
 2. Oxidation - chemical reaction with oxygen and other
  substances. (Iron bearing substances) , (red soil in Carolina
  & Virgina)
 3. Carbonic acid/Carbonation - Carbon dioxide dissolves in
  H2O to form carbonic acid. (found in soda), P,Na,Mg and
  Ca (forms caves)
 4. Acid Rain - sulfur from cars and coal/oil plants
 5. Plants/Animals (Lichens) - produce rock dissolving
  acids
CHEMICAL WEATHERING
Carbonation Clip

 http://www.youtube.com/watch?v=Sw58a4yjFtc
Details worn away by
chemical weathering
Acid Rain
Oxidation
Hydrolysis -Reaction of any
substance with water
Chemical Weathering-
Water molecules "pull" apart a
mineral (dissolve it)
Plants can grow on rocks and
produce weak acids that can
break down rock.
                  Organic
Lichen breaking
down rock
                  Weathering
Bird dropping weathering
                
         RATES OF WEATHERING
II. Rates of Weathering
        1. The rocks themselves - Igneous and metamorphic most
resistant, sedimentary least resistant because of pores.
       2. Surface Area – More surface area = faster weathering
       3. Climate - Warm and wet = chemical weathering
                   Cold and Dry = mechanical weathering
       4. Topography
http://streaming.discoveryeducation.
com/search/assetDetail.cfm?guidAss
etID=6B1E329E-5A77-4B36-BFA9-
1D307F75441C
Weathering
 Get on the online book and go to chapter
  14.
 Select the visual concepts and watch the
  clips on physical and chemical weathering.



http://my.hrw.com/tabnav/controller.jsp?isbn=003036339x
                              EROSION
IV. EROSION - The breakup and removal of rock by moving natural
agents (gravity, glaciers, wind, water)
A. Water Erosion
        1. Rain
               a. Sheet wash - thin sheets of soil removed
prevent by - grass, continued plowing, crop rotation, strip crop, terraces
                  b.Gullying - valleys in sloped land - farms
        2. Running water - most effective agent of erosion
                  a. stream, river, creek
                  b. Stream abrasion - grinding away of rock from bed or
bank.
                  c. The faster the river moves = more “stuff” it can carry
                          EROSION
B. Wind Erosion - just as water; only less powerful
       1. Abrasion - wearing down of particles
       2.Deflation - removal of loose particles by wind - the most
important effect by wind
       3. Dunes - sand piled up, moved by wind


C. Glaciers – most powerful agent of erosion
Gullying
DEFLATION
DUNES
Arches National Park

      Wind abrasion
                              EROSION
IV. EROSION - The breakup and removal of rock by moving natural
agents (rivers, glaciers, wind, water)
A. Mass movements - Earth material down a slope caused by gravity.
         1. Creep - Very, Very slow down slope movement of soil. (water
in soil adds to it)
                  a. Talus - Loose rock fragments at base of cliffs
           2. Landslides - sudden movement of bedrock or loose rocks down
a cliff.
           3. Slumps - small landslides on hills
           4. Mudflow - fast movement of water saturated clay and silt.
           5. Avalanche
TALUS
Landslide – mass movement
LANDSLIDE
LANDSLIDE
Landslide – mass movement
CREEP
Creep
SLUMPS
SLUMPS
SLUMP
MUDFLOW
The Colorado River weather and
eroded way for 1,000s of years
Brought to us by the Colorado
River

								
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