AIM: What is Weathering?

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AIM What is Weathering? Do Now Choose one of
the following pictures and describe what is/has
happened.
A
B
c
E
F
D
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• Weathering
• the breaking down of a rock into small pieces.

As Surface area increases the amount
of Weathering increases
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• II. Mechanical (Physical) Weathering
• - changing the size and shape of the rock.

Abrasion rocks hitting and smashing against
each other.
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• III. Types of Mechanical Weathering
• a) Frost Wedging

the expansion of frozen water in cracks of
rocks cause it to break. -This broken material is
called talus What happens to water
when it freezes?
Do Not Copy
Expands
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• b) Biological Activity -
• organisms, plants, burrowing animals, and humans
  break down rocks.

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• IV. Chemical Weathering
• changing the rocks chemical composition.
• forms a new material.
• Water is the most important agent.

Soluble a material that can be dissolved by
water.
Acid Rain Damage
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V. Types of chemical weathering

• Acid Rain
• - water combines with different elements to make
  acids.
• - this is known as Hydrolysis.
• - H2O carbon dioxide carbonic acid
• - H2O sulfur sulfuric acid (acid rain)

Do Not Copy
What material will all these acids react with?
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• Acid rain reacts with calcite and dolomite in the
  rocks (Limestone).
• This dissolves the rock creating Karst Topography
  (caves), stalactites and stalagmites.

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b) Oxidation - Water and oxygen react with metal
to create rust.
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VI. Rate of Weathering

• A) Rock Characteristics
• - Mineral composition and solubility of the rock
  (the minerals that make the rock) determine the
  rate of weathering.

Limestone
Granite
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• - amount of surface area determines amount of
  weathering

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• - Some rocks are more resistant (harder) to
  weathering. Mineral composition is the greatest
  determining factor.

Hoodoo
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• B) Climate
• - Temperature and moisture are the most crucial
  factors.
• - Chemical weathering is most effective
• in areas with high temperatures (heat) and
• abundant moisture (water).

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Closure In your Notes
Slate Headstone
Marble Headstone

• Explain the difference in weathering of the
  two headstones (roughly the same age). What
  caused the difference in weathering?

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Cleopatras Needle

2) Describe one factor that explains why
Cleopatras needle changed after it was brought
from Egypt to New York.
1900 - Egypt
Present Day - Central Park