CLASS LECTURE - Welcome to Grossmont College

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					       Weathering and Mass Wasting
   Physical Weathering

   Chemical Weathering

   Mass Wasting

   Human Induced Mass Wasting
                Weathering
The combined action of all processes that cause
 rock to disintegrate physically and decompose
                    chemically
           Physical Weathering
Physical weathering is the disintegration of earth
material without undergoing a chemical change.




  The result of physical weathering is to simply make
smaller pieces out of larger ones (thus more surface area
            for chemical reactions to occur).
          Physical Weathering
Frost action…
the repeated growth and
melting of ice crystals
small cracks…
when water freezes and
expands and can split
rocks apart
  Physical Weathering
Salt Crystal – Water evaporates
leaving salt crystals which
accumulate and break rocks
apart grain by grain
  Physical Weathering
Unloading occurs as
pressure on underlying
rocks is eased allowing
them to expand and crack,
creating a type of jointing
called sheeting structure
Weathering and Mass Wasting
   Physical Weathering

   Chemical Weathering

   Mass Wasting

   Human Induced Mass Wasting
  Chemical Weathering
the minerals that make up rocks are
    chemically altered or dissolved
              Chemical Weathering
Oxidation and
hydrolysis create softer
and bulkier minerals
more susceptible to
erosion and mass
movement

Carbonic acid action
dissolves minerals,
washing them away in
runoff
Weathering and Mass Wasting
   Physical Weathering

   Chemical Weathering

   Mass Wasting

   Human Induced Mass Wasting
                   Mass Wasting
  Mass wasting is spontaneous movement of soil,
  regolith, and rock under the influence of gravity




Many forms, depending on the speed of the motion and the
               amount of water involved
Unstable slopes mobilized by rain water
           caused a landslide




      La Conchita, CA 1995 landslide
A mudflow is the rapid down slope movement of
water- saturated soil.




                        Mudflow, Pacific Palisades, CA.
Rock Falls and
Rock Slides
Weathering and Mass Wasting
   Physical Weathering

   Chemical Weathering

   Mass Wasting

   Human Induced Mass Wasting
      Human Induced Mass Wasting
Piling up unstable materials or undercutting natural
        supports for slopes or rock masses




 (cutting and filling to build and to extract mineral
         resources is termed scarification)
Weathering and Mass Wasting
   Physical Weathering

   Chemical Weathering

   Mass Wasting

   Human Induced Mass Wasting

				
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