Chapter 12
• Weathering
• The breakup of
rock due to
exposure to
processes on
the Earth’s
surface
• Mechanical
Weathering
• There are 4 types
of physical
weathering…..
• Breaking a rock
into smaller pieces
WITHOUT
changing it’s
composition
• DISINTEGRATION
or “physical”
weathering
• Frost Wedging
• Water in the
cracks of rock
freezes, expands
and pushes the
rock apart,
breaking it
• Remember, water
EXPANDS as it
freezes
• Abrasion
• TO SCRATCH
• Water, wind or
glaciers can move
sand, gravel and
other rocks
causing them to
scrape against one
another, wearing
each other away
• Plant and
animal action
• Tree roots can
grow into rocks,
breaking them
apart
• Animals can dig
into the soil,
breaking rocks
and allowing water
to weather it
• Exfoliation
• Rocks that get
pushed upward
become exposed
to the air,
breaking or
peeling off
• Chemical
Weathering
• There are 3 types
of chemical
weathering…..
• A rock’s minerals
are changed into
different
substances; hence
the composition
changes
• DECOMPOSITION
• Hydrolysis
• Reaction with
water
• Water can
dissolve
minerals
• Water can
combine with
gases to make
acids, eating
away at rock
• Carbonic Acid
• Acid Rain
• Water combines
with air
pollutants like
Nitrogen and
Sulfur to create
acids
• Oxidation
• Chemical
reaction of
oxygen with
other
substances,
thus causing
rust
• Rates of
Weathering…..
• Mechanical
Weathering….
• Chemical
weathering….
• Prefers a cold,
dry climate
• Prefers a warm,
moist climate
• Mineral
composition…
• Some minerals are
more resistant to
weathering, like
quartz
• Sandstone
weathers easily
while marble does
not