Weathering and Erosion

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Weathering and Erosion

• And other adventures in Earth Science!

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How did this happen?
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Activity Idea Weathering Walk

• Start with the question What would happen if
  this building were abandoned?.
• Take a walk around the school and see if you can
  find any signs of weathering. Even better, meet
  your class out at a park on a Saturday morning
  for an extra credit weathering hike!

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Types of Weathering

• Mechanical Weathering is a term that refers to a
  physical breakdown of rock material.
• Ice wedging, Sheeting, Plants and Animals

• Chemical Weathering is a term that refers to
  alteration of the rock material on a mineral
  level.
• Hydrolysis,Dissolution, Oxidation

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Ice wedging (Mechanical)

• The stress on a rock generated each time water
  freezes is about 110 kg per cm squared, or
  approximately equal to slamming the rock with a
  sledgehammer.

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Sheeting (Mechanical)

• Expansion joints that are parallel to the earths
  surface. These occur as exposed rock is released
  from pressure. Frequently occurs in quarries.

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Plants and Animals (Mechanical)

• Pressure from growing roots, burrowing animals
  actually dig out the rock, thereby increasing
  surface area exposed to the elements.

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Hydrolysis (Chemical)

• This term refers to the chemical union of water
  and a mineral.
• Example water and carbon dioxide combine to form
  carbonic acid, which changes feldspar (a common
  mineral in many rocks) into clay.
• Clay, in turn, becomes shale, our most abundant
  sedimentary rock.

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Dissolution (Chemical)

• This term refers to rock material passing
  directly into solution.
• Why is halite not a rock commonly found on the
  ground in Ohio?
• Caves and Karst Topography

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Oxidation (Chemical)

• This refers to Oxygen bonding to a mineral.
• Iron and Oxygen form Iron Oxide (rust!)

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The Earth/Apple Demonstration

• Determine percentage of the earth that is land. (
  Tossing around a globe?
• Break down an apple into these proportions 3/4
  water, 1/8 land that is not available for use
  such as deserts and polar ice caps, 3/32 land
  that cannot be used for food production due to
  current use or past misuse, 1/32 land available
  for food production.

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Whats going on here?
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Lets look to our (very recent) past.
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Erosion

• The term erosion describes how water, ice, wind
  and gravity move weathered material.
• Plate tectonics and erosion
• The term isostasy refers to the gravitational
  adjustments made by the crust.

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Erosion by Water

• River systems are the single most important agent
  of erosion, producing stream valleys, the most
  prevalent landform on the continents.
• River systems constantly move toward equilibrium.
• What are some ways that rivers erode?
• What landforms are produced when sediment is
  deposited?

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Erosion by wind

• Wind erosion can manifest itself by deflation
  (lifting up loose soil into the air) and abrasion
  (sandblasting).
• Wind erosion can form ventifacts, (pebbles
  polished by abrasion, with a particular shape)
  yardings (large linear ridges), and deflation
  basins (broad, shallow depressions).
• Most commonly, wind erosion and deposition is
  associated with dunes.

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Erosion by Ice

• Glaciers erode in two ways by glacial plucking
  and by abrasion.
• Glacial plucking involves utilizing ice wedging
  to quarry out rocks underneath the glacier,
  which then are incorporated into the ice.
• Abrasion is a filing process. This process
  produces Glacial Striations.

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Erosion by Gravity (Mass Movement)

• The term Mass Movement describes how material is
  transferred downslope by gravity.
• Factors important in mass movement include
  saturation, tectonic movement (earthquakes),
  angle of slope, and freezing and thawing.
• Major types of mass movement are debris flow,
  creep, and landslides.

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