Transcript Slide 1

AIM: What is Weathering?
Do Now – Choose one of the following
pictures and describe what is/has
happened.
I. Weathering
the breaking down of a rock into small
pieces.
As Surface area increases the amount of
Weathering increases
II. Mechanical (Physical)
Weathering
- changing the size and shape of
the rock.
Abrasion:
rocks hitting and
smashing against
each other.
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
Do Not Copy
What happens to water
when it freezes?
b) Biological Activity organisms, plants,
burrowing animals, and
humans break down
rocks.
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
V. Types of chemical weathering
a) 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?
•Acid rain reacts
with calcite and
dolomite in the
rocks (Limestone).
•This dissolves
the rock creating
Karst Topography
(caves),
stalactites and
stalagmites.
b) Oxidation
- Water and oxygen react with metal
to create rust.
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.
Granite
Limestone
- amount of surface area determines
amount of weathering
- Some rocks are more resistant (harder) to
weathering. Mineral composition is the
greatest determining factor.
In the diagram below, which
letter rock is most resistant to
weathering?
Hoodoo
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).
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?
Cleopatra’s Needle
2) Describe one
factor that
explains why
Cleopatra’s
needle changed
after it was
brought from
Egypt to New
York.
1900 - Egypt
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