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.
What is changing
about the object
besides the
shape?
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.
What is making
the rocks
abrade in the
stream?
III. Types of Mechanical Weathering
a) Frost Wedging
What happens to water
when it freezes?
- water expands
when it freezes
- this creates
pressure that
cracks the rock
b) Biological Activity organisms(plants,
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 + sulfur = sulfuric acid (acid rain)
What mineral 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 affects the
amount of weathering
WHY?
- Some rocks are more resistant (harder) to
weathering because of their composition
(minerals).
In the diagram below, which
letter rock is most resistant to
weathering?
Hoodoo
B) Climate:
- Temperature and moisture help determine
the type and amount of weathering.
- 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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