Chapter 8 Part 1

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Chapter 8Part 1

• Weathering, Soils and
• Mass Movement
• GRB Pages 62 - 71

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Weathering and Erosion

• Weathering - Def. - the break down of rocks that
  have been exposed to the atmosphere.
• Once the rocks are broken down, the pieces are
  transported from one place to another. This
  process is called erosion.
• Erosion is caused by wind, moving water (streams,
  waves, ocean currents), ice (glaciers), and by
  gravity.
• VIF - Most erosion that takes place on Earth is
  caused by moving water

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2 Types of Weathering

• Chemical weathering
• rocks break down as their minerals change in
  composition (they become different substances).

•   Mechanical weathering rocks are broken down
  into smaller pieces without changing their
  composition (what theyre made of).
• AKA - physical weathering

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Types of Mechanical Weathering - 1

• Ice wedging/frost action
• water enters small cracks in the rock.
• When it freezes, it expands and forces the crack
  to open more.
• The process repeats over again until the rock
  breaks apart.

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Mt. Brewster looks solid, right?
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Close up shows jagged rocks from FROST wedging!
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Eventually, the rock splits from repeated frost
action!
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Types of Mechanical Weathering - 2

• Abrasion
• It is the physical wearing down of rocks as they
  rub or bounce against each other. This process is
  most common in windy areas, under glaciers, or in
  stream channels.
• It can also happen during rock slides

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Types of Mechanical Weathering - 3

• Wetting and drying
• breaks up rocks that are made from clay.
• When they are wet they expand, and they shrink as
  they dry.
• As this repeats over and over, the clay becomes
  weak and cracks (think of all the projects you
  have made out of claythey all crack and fall
  apart)!

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Types of Mechanical Weathering - 4

• Exfoliation
• soil and rock is removed (glaciers or uplifting),
  exposing rock found deep underground.
• This releases the pressure causing the surface of
  the rock to expand and eventually crack.

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Types of Mechanical Weathering - 5

• Plant Roots
• The roots of trees often wedge in between cracks
  in rocks and force apart rocks even further!

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