Transcript Physical/Chemical Weathering

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 smaller
pieces.
What is changing about the object?
More pieces = More surface area
As weathering increases the surface area
increases (direct relationship).
II. Mechanical (Physical) Weathering
changing the size and shape of
the rock.
a) Abrasion:
rocks hitting and
smashing against
each other.
What is making the rocks abrade in the
stream?
b) Frost Wedging
What happens to water
when it freezes?
- water expands
when it freezes
- this creates
pressure that
cracks the rock
c) Biological Activity organisms(plants,
animals and humans)
break down rocks.
(organisms abrade
rocks)
III. Chemical Weathering
changing the rocks chemical composition
to create a new material.
Water is the most important agent during
chemical weather because most materials are
soluble (a material that can be dissolved by
water).
a) Acid Rain
- water combines with different elements
to make acids, known as Hydrolysis.
- H2O + sulfur = sulfuric acid (acid rain)
Which minerals
will all these
acids react
with?
acid rain damage on trees
•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.
IV. Rate of Weathering
Depends on…
a) Rock Composition. Some rocks are more
resistant (stronger) to weathering because
of their composition (minerals).
Granite
Limestone
In the diagram below, which letter
rock is most resistant to weathering?
Hoodoo
b) amount of surface area affects the
amount of weathering
WHY?
c) 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
Present Day Central Park