Download What is mechanical weathering?

What is mechanical
weathering?
By. Mr. White
Go Panthers,
Keep Pounding
Learning Objective

Students will explain the ways that
Earth's surface is worn away by
mechanical weathering.
GPKP
2
Key Terms



weathering
chemical weathering
mechanical weathering
GPKP
3
Weathering





The breaking down of rocks and other
materials on Earth's surface is called
weathering.
Newly made bricks are bright red.
They have sharp comers and edges.
Old bricks are darker red.
They have rounded comers and edges.
GPKP
4
Kinds of Weathering




There are two kinds of weathering.
Chemical weathering occurs when the
chemical makeup of the rocks changes. The
sizes and shapes of the rocks may also
change.
Mechanical weathering involves only
physical changes, such as size and shape.
The chemical makeup of the rocks does not
change.
Mechanical weathering occurs as a result of
temperature changes, ice wedging, and root
action.
GPKP
5
Temperature Changes





Heat makes things expand, or become larger.
Cooling makes things contract, or become
smaller.
During the day, heat can cause the outside of a
rock to expand.
At night, the outside of the rock cools and
contracts.
The repeated heating and cooling of the
rock's surface each day may cause pieces of
it to flake or peel off.
GPKP
6
Ice Wedging





Water enters cracks in rocks.
When the temperature drops below freezing,
water freezes and expands.
The expanding water is like a wedge, making
the crack wider.
After the repeated freezing and melting of
water, the rock breaks apart.
Potholes in streets are caused by ice
wedging.
GPKP
7
Over long periods of time,
weathering changes the shape of
mountains
GPKP
8
Root Action




Plant roots in search of minerals and
water can grow into cracks in rocks.
Tree roots may cause cracks in
sidewalks by lifting up the sidewalk.
The pressure of the growing root can
make the cracks in rocks larger.
As the roots grow, they can break the
rocks apart.
GPKP
9
Growing plant roots can lift up
sidewalks
GPKP
10
Checking Concepts
1.
2.
3.
4.
Is breaking a rock into pieces chemical
or mechanical weathering?
What kind of weathering causes
potholes?
Does root action cause mechanical or
chemical weathering?
What kind of weathering do changes in
temperature cause?
GPKP
11
Answers
1.
2.
3.
4.
Mechanical weathering
Mechanical weathering
Mechanical weathering
Mechanical weathering
GPKP
12
The End