Download Weathering

Forces That Shape Our
Earth:
Weathering
And
Erosion
Weathering & Erosion:

Erosion and weathering are major
forces that shape Earth’s surface.

For example, the Grand Canyon
was formed through erosion by the
Colorado River running through it.
What is weathering?
Weathering is the breaking down
of rocks and earth materials into
smaller pieces called sediment.
There are two types of weathering:
1. Mechanical /Physical
2. Chemical
So what is erosion?
Erosion:
The movement
of weathered
rock by wind,
water, glaciers,
and gravity.
Types of Weathering:
Mechanical or Physical:
Rock is physically broken into smaller
pieces (larger pieces become smaller
pieces of the same rock)
Chemical:
Rock is chemically changed (like
rusting or dissolving away).
5 Ways that Physical
Weathering Occurs:
1.
2.
3.
4.
5.
Release of Pressure
Freezing & Thawing
Animal Actions
Plant Growth
Abrasion
Release of Pressure
 As
the surface of a rock is
eroded, the rock begins to release
pressure.
 This pressure causes top layers
of the rock to crack and flake off.
Release of pressure:
(Rock cracks like an egg shell.)
Freezing & Thawing
When water in the
cracks of rocks freezes,
it expands causing the
crack to enlarge or get
bigger. The ice melts &
refreezes over and over,
breaking the rock apart.
Result of Freezing & Thawing
Animal Actions
Animals
dig (burrow) through
the ground to make their
homes.
This digging loosens the soil
and breaks the rocks apart.
Plant Root Growth
Plants roots can grow into
cracks in the rock, slowly
breaking them apart.
Abrasion


Sand and other rock particles in
wind, water or ice can wear
away exposed rock surfaces.
It is like using sandblasting or
sandpaper on wood.
Chemical Weathering
The process that breaks down
the surface of rock by
chemical changes.
5 Ways that Chemical
Weathering Occurs:
1.
2.
3.
4.
5.
Water
Oxygen
Carbon Dioxide
Living Organisms
Acid Rain
Water
Water
dissolves rocks over
time.
Water
is the most important
cause of chemical weathering
Oxygen
 Oxygen
+ Water + Iron = Rust
through the chemical reaction
called oxidation.
 Rock
will become crumbly, soft,
and appear reddish-brown in
color.
Rusted rock on hillside
Carbon Dioxide
CO2 + rainwater = Carbonic Acid
Carbonic acid weathers softer rock
like limestone & marble as it seeps
into spaces in rock.
Examples: sinkholes and caves.
Living Organisms
The
roots of plants make a
weak acid that slowly
dissolves rocks around the
plant.
Lichens grow on rock
Acid Rain
Acid
rain causes rocks to
weather very rapidly.
Acid
rain is more common
around volcanic areas.