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WEATHERING MINE

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					         WEATHERING




Definition: The physical and chemical
  processes that break down rock on
  earth’s surface.
      2 Types of Weathering
PHYSICAL/ MECHANICAL WEATHERING – rocks are
broken apart increasing the surface area.


ROCK BEFORE WEATHERING =
ROCK AFTER WEATHERING (just smaller)

CHEMICAL WEATHERING – Chemical reactions CHANGE
minerals.
ROCK BEFORE WEATHERING ≠ ROCK
AFTER WEATHERING
 PHYSICAL WEATHERING
INCREASES SURFACE AREA
MORE CHEMICAL WEATHERING CAN OCCUR
  PHYSICAL WEATHERING
 MOST   IMPORTANT IN OUR CLIMATE
FROST ACTION – FROST WEDGING
                         ALTERNATE
                         FREEZE
                         AND THAW


                         Water
                         expands
                         when frozen
ROCKS ARE
CRACKED BY
WATER
FREEZING
EXAMPLES: POT HOLES
AND FROST HEAVES
   PHYSICAL WEATHERING –
        ROOT ACTION
PLANT ROOTS UPLIFT AND FRACTURE
 ROCK
   PHYSICAL WEATHERING -
         ABRASION
ROCK PARTICLES GRIND AGAINST ONE
            ANOTHER




   WATER               WIND
    PHYSICAL WEATHERING
 EXFOLIATION – PEELING AWAY
          OF ROCK
 Unloading  – due to reduced pressure at
 earth’s surface rocks will expand but they
 will crack because they are brittle

 FluctuatingTemperatures will cause rocks
 to contract and expand causing cracks
 Examples: deserts and mountains
PHYSICAL WEATHERING -
     EXFOLIATION
      EXAMPLES OF CHEMICAL
          WEATHERING
   OXIDATION OCCURS when free oxygen
    combines chemically with metallic
    elements (usually iron)
                       AKA RUST
           CARBONATION
Water containing carbonic acid dissolves
 minerals (all rain water is slightly acidic)
 Most strongly affected are calcite
 minerals:
     limestone and marble
  CARBONATION
Stalagmites and stalactites
 CARBONATION – SINK HOLES
 KarstTopography
forms caves, caverns,
and sinkholes
CAVES AND SINK
HOLES
    CHEMICAL WEATHERING
         HYDRATION
 OCCURS    WHEN Water combines with
 minerals – most often in granite (mica and
 feldspars) to form CLAY
 WHAT KIND OF CLIMATE
SUPPORTS WEATHERING?
HIGH
PPT
↑
↑
↑
↑
↑
↑
↑
LOW
PPT

       COLD →→→→→→→→→→ HOT
CLIMATE CONTROLS WEATHERING
  PHYSICAL WEATHERING:
     COLD AND MOIST
     ALTERNATE FREEZE / THAW

  CHEMICAL WEATHERING:
     WARM AND MOIST
IN BOTH CASES – WATER IS THE PRIMARY
INGREDIENT THAT PROMOTES WEATHERING
Differential Weathering due to
  Climate and Composition
 • Masses of rock do not weather uniformly due
   to regional factors and composition.
 • Results in many unusual and spectacular rock
   formations and landforms
  WHICH LAYER IS MORE
RESISTANT TO WEATHERING?
     LEAST RESISTANT?



         A           D
                 C
             B
YOU MIGHT ALSO SEE IT LIKE
          THIS.
WHICH DIAGRAM IS AN ARID
CLIMATE? HUMID CLIMATE?
          A     B




Humid –              Arid –
more                 more
rounded              angular
    THE END PRODUCTS OF
        WEATHERING

CALLED SEDIMENTS OR SOIL

SOIL: a combination of sediment, rock
 minerals, and humus (organic material
 from biologic activity)
  SOIL – THE PRODUCT OF
       WEATHERING
AFTER THOUSANDS OF YEARS…
          SOIL HORIZONS
Layers that develop as a result of the
  weathering processes, biologic activity,
  and leaching (flow of water through rocks)
Soil Development
            Size and thickness
            of each horizon
            depends on:
            Climate
            Vegetation/
            Biologic Activity
            Slope (gradient or
            incline)
            Time
        2 TYPES OF SOIL
TRANSPORTED SOIL: SOIL CARRIED BY
 EROSION AND DEPOSITED ON THE
 BEDROCK (MOST SOIL IS TRANSPORTED)
  BEDROCK BENEATH ≠ SOIL ABOVE

RESIDUAL SOIL: SOIL FORMED BY THE
 WEATHERING OF THE BEDROCK
 DIRECTLY BENEATH IT
  BEDROCK BENEATH = SOIL ABOVE
TRANSPORTED SOILS DUE TO …
   WEATHERING SUMMARY
         WEATHERING –
 PHYSICAL
 INCREASES SURFACE AREA -
 COLD/HUMID CLIMATE

         WEATHERING –
 CHEMICAL
 WARM/HUMID CLIMATE

   BOTH CASES, WATER IS THE
 IN
 PRIMARY INGREDIENT

				
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posted:10/6/2011
language:English
pages:35