Weathering

1
Weathering
2
Weathering and Erosion

• Weathering is the chemical or physical breakdown
  of a rock or mineral due to exposure to the
  atmosphere.
• Erosion is the removal or transport of material
  by 5 possible agents running water,
  glaciers, waves, wind, and
  gravity.
• Humans and animals may also play a part in
  erosion.

3
Types of Weathering

• There are two major types of weathering
• 1. Mechanical (physical) breakdown of rock or
  mineral. Just breaks it into smaller pieces,
  composition of the material is NOT changed!!
• 2. Chemical changes the composition of
  material as it breaks down.

4
Physical (Mechanical) Weathering

• Some ways physical weathering can occur
• 1. Freezing and thawing of moisture in rock
  openings causing rock disintegration. (Water
  expands as it freezes, this breaks the rock into
  pieces. Occurs A LOT in our state causes most
  potholes!!!)

Frost Wedging animation
5
2. Erosion of upper rock causes underlying rock
to expand resulting in cracking and peeling of
rock in slabs. Think of onion skin layers and
peeling them off!!
6

• 3. Organic Activity plant roots or animals
  like burrowing worms can cause rock to breakdown.

7

• 4. Wetting and Drying - addition of water to
  mineral structure causes structure to expand.

8
Chemical Weathering

• There are also several different types of
  chemical weathering
• 1. Hydrolosis chemical reaction between water
  and other substances.

(feldspar weathered into clay by hydrolosis)
9

• 2. Carbonic Acid dissolving of substances by
  acids in water often leaving insoluble remains.

10

• 3. Oxidation chemical reaction of a substance
  with oxygen causing a rust or patina to form.

11
Weathering and Climate

• Climate plays a very important role in
  weathering.
• The temperature and amount of moisture influences
  the type of weathering that will occur.
• Warm and wet climates produce mostly chemical
  weathering.
• Cool and slightly wet climates produce mostly
  physical weathering.

12
Cleopatras Needle in Egypt warm dry climate
little to no weathering occurs
Cleopatras Needle was moved to New York and has
weathered considerably in only 80 years due to
the cold and wet climate.
13
Weathering and Resistance

• The harder the rock or mineral is, the more
  resistant it will be to weathering.
• Any rock with quartz will be quite resistant due
  to quartzs hardness.
• What is quartzs hardness?
• Rocks made mostly of calcite, a very soft
  mineral, will be easily weathered.
• What is calcites hardness?

14
Porosity and Permeability

• Porosity The percentage of pore space in a
  material
• Permeability The ability of a material to let
  liquid (water) pass through it.
• Impermeable When something will not let liquids
  pass through it (usually water is the liquid).

15
(No Transcript)
16
Permeability

• If something has
• Low Porosity, then
• permeability will be
• SLOW
• If something has
• High Porosity, then
• permeability will be
• FAST