WEATHERING

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WEATHERING EROSION
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What is Weathering?

• Process by which rocks on or near Earths surface
  break down and change.

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MECHANICAL WEATHERING

• Also called physical weathering.
• Changes rocks size and shape but NOT composition.
• EX
• Frost Wedging freezing water expands in rock
  causing cracks
• Pressure
• from tree roots
• removal of rock layers above. When rock layers
  are removed, rock can expand causing cracking.

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CHEMICAL WEATHERING

• Changes rocks composition
• New minerals are formed
• Determined by
• Composition of rock
• Calcite dissolves in acidic water
• Temperature
• As temperature increases so does rate of
  weathering

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Water

• Hydrolysis- reaction of water with other
  substances.

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Oxygen

• Oxidation- reaction of oxygen with water.
• Iron reacts with oxygen creates rust
• Magnetite oxgyen hematite

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Acids

• Carbon dioxide, nitrogen oxides, and sulfur
  dioxides from fossil fuels create acids in
  atmosphere.
• Cause acid rain.
• These acids dissolve minerals in rocks.
• Can also tarnish metals

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WHAT AFFECTS THE RATE OF WEATHERING?

• Climate
• Temperature precipitation in an area
• Chemical weathering more common where
  temperatures precip are higher
• Physical weathering more common where dry, and
  cold (freezing thawing occur more common)

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• Rock type composition
• Hardness
• Sedimentary rocks more easily weathered than hard
  igneous or metamorphic

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• Surface area
• Mechanical weathering breaks rock up into smaller
  pieces creating more surface area for chemical
  weathering to occur

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• Topography other variables
• Sloped areas expose fresh rock after erosion.
  Fresh rock can then be weathered.
• Decaying organic matter releases CO2 which
  creates acid which weathers rock faster.

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WHAT IS EROSION?

• Transporting weathered materials from one place
  to another.

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WATER

• Steeper slopes, faster water flows
• Faster water flows, more erosion occurs
• Rill erosion- creates small channels
• Gully erosion- creates deep, wide channels

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COASTAL EROSION

• Ocean waves tides also cause erosion
• Constant erosion of beaches leads to creation of
  sand bars which eventually become barrier islands.

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ICE

• Glaciers
• Scrape out large sections of earths landscape
• Carry large rocks debris over many miles

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WIND

• Occur in areas with limited rainfall and high
  temperatures
• Most of these areas have very little plant-life
  to hold soil in place
• Creates dunes

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PLANTS, ANIMALS, HUMANS

• Minor impact compared to water, wind, glaciers
• When humans excavate land, cause erosion, leads
  to water pollution
• When animals burrow, shovel dirt somewhere else.

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DAILY QUIZ 1

• The breakdown of rocks is
• a. Erosion b. Weathering c. Mass wasting
• Oxidation is a form of
• a. Mechanical weathering b. Chemical weathering
• When a rock changes in size shape but not
  composition, it went through
• a. Mechanical weathering b. Chemical weathering
• Wind erosion can create
• a. Glaciers b. Mass wasting c. dunes
• Coastal erosion results from
• Ocean Waves
• Glacier formation
• Chemical weathering