Download Ms. Baker`s Science Class

Chemical & Mechanical Weathering
1. Investigation
• Chemical Weathering (4 types)
• Mechanical Weathering (5 types)
2. Complete pages 73 about weathering.
Resources: readings, “How to make Mudpie” movie,
textbook (orange) p 295-296, website:
http:facweb.bhc.edu/academics/science/harwood
r/geol101/study/weather.htm
Mechanical & Chemical Weathering
1. What are the four types of chemical weathering?
Oxidation, Carbonation, Acids, Hydration
2. What are the five types of mechanical weathering?
Root action, Thermal expansion, Hydraulic Action,
Organic Activity, Gravity
Chemical Weathering
Definition: the process that
breaks down rock through
chemical changes
Chemical Weathering
1. Oxidation
• Combines oxygen with
another substance in
the rock
• Usually changes
color of rock
2. Carbonation
• Happens in rocks
that contain calcium
carbonate
(limestone)
• Speeds up as the
temperature
decreases
3. Acid Rain
• Formed by sulfur
and nitrogen
compounds
• Will cause rocks
to fall apart
4. Hydration
• Incorporation of
H+ and OH- ions
from H2O
• Causes an increase
in volume
• Adds stress within
the rock
Mechanical Weathering
Definition: the process that
breaks down rock physically
Mechanical Weathering
1. Root Action
• As roots grow,
they break rocks
apart
2. Thermal Expansion
• Temperature
changes: Rocks
heat up in the day
and as the
temperature drops
greatly at night,
the rocks can flake
easily (defoliate)
• Common in deserts
2. Thermal Expansion
(continued)
• Freeze/thaw will
also deposit water
in cracks
• When water
freezes, the ice
pushes outward
causing pieces of
the rock to break
off
3. Hydraulic Action
• Water (usually from
powerful waves) rushes
into cracks in rocks
• A tiny bit of air is
compressed at the
crevice of the crack
• When water recedes, the
air is forcefully released
taking away fragments of
rock with it
4. Organic Activity
• Mosses and lichens
attach to rocks
(note: lichens cause
physical and
chemical breakdown
of the rock)
4. Organic Activity
(continued)
• Plant roots exert
physical pressure
on rock cracks
(note: plants
form an acid on
the rocks that
further break
down the rock)
5. Gravity
• Large rocks
often fall from
mountainsides
and as they hit
bottom they
break into
smaller pieces