Transcript Forces That Shape Our Earth: UNIT 3: Weathering And Erosion Weathering & Erosion: Why is this important? Erosion and weathering are major forces that shape the world around.

Forces That Shape Our
Earth:
UNIT 3:
Weathering
And
Erosion
Weathering & Erosion:
Why is this important? Erosion and
weathering are major forces that shape the
world around us. Understanding these
forces helps us to understand the way our
land is shaped – from rivers to canyons.

For example, the Grand Canyon
was formed through erosion by the
Colorado River running through it!
People play a part in the
way and amount that our
soil erodes around us. It
is important for us to
understand how erosion
works and the effects on
soil.. Especially since we
depend on soil for our
food production! If we
don’t take care of the soil,
we will starve.
What is weathering?
Weathering: The breaking down
of rocks into smaller pieces.
1. Mechanical /Physical
2. Chemical
Hulk
Rock
Smash!
Types of Weathering:
Mechanical/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 Agents of Mechanical
Weathering:
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
 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 & over,
breaking the rock apart.
Result of Freezing & Thawing
Animal Actions
Animals
dig (burrow) through
the ground to make their
homes. This loosens the soil &
breaks apart rocks.
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.
Like sandblasting or sandpaper
on wood
Chemical Weathering
The process that breaks down
the surface of rock by
chemical changes.
1.
2.
3.
4.
5.
5 Agents of Chemical
Weathering
Water
Oxygen
Carbon Dioxide
Living Organisms
Acid Rain
Water
 Water
dissolves rock
 Water
is the most important cause of
chemical weathering
 Moving
water is THE STRONGST
weathering force that changes the
land we see
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.
Ex: sinkholes, 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.
So what is erosion?
Erosion:
The movement
of weathered
rock by wind,
water, glaciers
& gravity