Transcript Forces That Shape Our Earth:

Forces That Shape Our
Earth:
UNIT 3:
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: The breaking down
of rocks into smaller pieces.
1. Mechanical /Physical
2. Chemical
Hulk
Rock
Smash!
So what is erosion?
Erosion:
The movement
of weathered
rock by wind,
water, glaciers
& gravity
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.
6.
Water
Freezing & Thawing
Animal Actions
Plant Growth
Wind
Gravity
Water
 As
water flows over rocks it
breaks off the rough edges and
causes them to be smooth or
carves away parts of the rock
creating holes.
Result of Weathering by Water
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.
Wind


Sand and other rock particles in
wind can wear away exposed
rock surfaces.
Like sandblasting or sandpaper
on wood
Gravity
 Gravity
pulls down rocks or sediment from
high places and when it hits other rocks it
will cause them to break into pieces.
 Could
be caused by landslides or rockfalls.
Results of Gravity
Chemical Weathering
The process that breaks down
the surface of rock by
chemical changes.
1.
2.
3.
5 Agents of Chemical
Weathering
Water
Oxygen
Acid Rain
Water
Water
Water
dissolves rock
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
Acid Rain
Acid
rain causes rocks to
weather very rapidly.