Science 5 #Grade 5

1. Weathering

4. At the end
of the
lesson, you
should be
able to:
explain the process of
weathering; and
2
enumerate the factors
affecting weathering.
3
define weathering;
1

5. Weathering
Fractures on rocks can eventually
cause weathering or breaking of
rocks into pieces.
Weathering is the
process of wearing
away or breaking
down of rocks into
smaller pieces.
This continuously
changes the shape
of Earth’s surface.

6. Weathering
Fractures on rocks can eventually
cause weathering or breaking of
rocks into pieces.
This can be caused by
physical breakdown of
rocks or with the help
of chemicals that
dissolve parts of rocks
slowly.
Agents of weathering
are factors that enable
breakdown or
dissolving of rocks.

7. Mechanical Weathering
Rock fragments
Mechanical
weathering is
the
breakdown of
rocks from
physical
processes.
The agents of
mechanical
weathering
are
temperature,
wind, water,
abrasion, and
living things.

8. Factors Driving Mechanical
Weathering
Temperature
 A rock that is constantly exposed to
changing temperature is affected gradually.
 Rocks contract when it is cold and expand
when it is hot.
 The continuous contraction and expansion
of rocks will result in cracks.

9. Factors Driving Mechanical Weathering
The water inside wet rocks freezes
when the weather is too cold.
Temperature
• Water that seeps through small
holes in rocks can help
increase the size of cracks.
• Water that is inside small
cracks can expand as it freezes
into ice when the weather gets
cold.

10. Factors Driving Mechanical Weathering
The water inside wet rocks freezes
when the weather is too cold.
Temperature
•During hot weather, water
contracts as it thaws.
•The process of expansion
and contraction of water
inside cracks can break
down rocks.

11. Temperature changes cause repeated expansion and contraction of
water and this results to weathering.
Factors Driving Mechanical Weathering

12. Factors Driving Mechanical
Weathering
Wind and Water
 Wind and water can cause rocks to tumble
or bump into each other repeatedly which
cause them to crack or break.
 Wind and flowing water bring with it small
materials that rub and gradually scrape the
rock surfaces.

13. Factors Driving Mechanical Weathering
Horseshoe bend in Grand Canyon where rock formations were shaped by the water.

15. Factors Driving Mechanical Weathering
Abrasion in pebbles caused by
the waves in the ocean.
Abrasion
• Abrasion is the rubbing
together of materials which
results in the wearing away
of its surface.
• Repeated abrasion results in
polished or smooth rock
faces.

16. Factors Driving Mechanical Weathering
Plant roots penetrating into
the rocks
Living Things
• Living things like plants,
animals, and humans can
cause breaking down of
rocks.
• Plant roots can force through
cracks and eventually break
down rocks.

17. Factors Driving Mechanical Weathering
Burrowing animals like mongoose, can
also contribute to weathering
Living Things
•Actions of animals
such as burrowing
can create holes
and can also force
rocks to crack and
eventually break.

18. Factors Driving Mechanical Weathering
Quarrying of rocks by humans
Living Things
•Humans use rock resources
to build roads, shelter, and
more.
•Humans also use rocks
directly or expose them to
weathering through other
agents.

19. ● Chemical weathering is the
breaking down of rocks through
chemical changes that involve
water, acids, and gases like
oxygen.
Chemical Weathering
Chemical weathering
of a statue

20. Water and Formation of Acid
● Water and acids can combine chemically with minerals that
are exposed in rocks. Minerals that are chemically combined
with water can be washed away and leave holes on rocks.
● Carbon dioxide can combine with water chemically and form
carbonic acid, which can dissolve limestone.
Factors Driving Chemical Weathering

21. Factors Driving Chemical Weathering
Corrosion of a statue due
to acid rain.
Water and
Formation of Acid
•Acid rain, which results
from air pollutants
combined chemically
with rainwater, also
dissolves minerals in
rocks.

22. Factors Driving Chemical Weathering
Rusting of rocks that are
rich in iron.
Oxidation
•Oxidation can cause
reactions to some
minerals when exposed to
oxygen.
•The iron in rocks form rust
when exposed to oxygen.

23. Factors Driving Chemical Weathering
Rusting of rocks that are
rich in iron.
Oxidation
•When rust
formation
increases in rocks,
it will eventually
break down rocks.

24. Role of
Weathering
in Soil
Formation
Some weathered materials are carried
and deposited to other areas by
different agents such as wind and water.
Some weathered materials change into
sedimentary rocks when cemented
together underwater.
However, weathered materials can also
collect for a long period of time and
eventually become soil.

25. Role of Weathering in Soil Formation
Weathering of rocks result to the
formation of soil.
Soil formation begins with the
weathering of rocks.
Soil is a mixture of broken down
fragments of rocks, air spaces, water,
and organic matter (material from dead
plants and animals).

26. Steps in soil formation
Role of Weathering in Soil Formation
 Plants that grow on weathered
rocks help in breaking it down
more.
 Plants are able to use the
nutrients from the minerals in
rocks.

27. Steps in soil formation
Role of Weathering in Soil Formation
 When plants die, they become
part of the organic matter in the
soil.

28. Steps in soil formation
Role of Weathering in Soil Formation
 More plants will be able to grow
on the soil and this also means
that more plants are able to draw
out the minerals from rocks.

29. Steps in soil formation
Role of Weathering in Soil Formation
 Animals will survive in areas with
plants.
 When animals die, they too add to
the organic matter.

30. The usual soil profile.
Role of Weathering in Soil Formation
 The soil has different layers and each layer is called a
horizon.
 The combined layers of soil are referred to as its profile.
 A typical soil profile can give a glimpse of how the soil is
formed.

31. The usual soil profile.
Role of Weathering in Soil Formation
 The lowest horizon is the bedrock.
 The bedrock comprises the rock that is often the parent
material of the soil.
 Weathering of the bedrock starts the soil formation.

32. The usual soil profile.
Role of Weathering in Soil Formation
 Above the bedrock is the parent rock which is made up
of residual bedrock and followed by the subsoil horizon
which is made of loose, slightly weathered rocks, and
exposed minerals with very little organic matter.

33. The usual soil profile.
Role of Weathering in Soil Formation
 Above the subsoil is the topsoil, a horizon with the
complete mixture of weathered rocks, organic matter,
air, and water.
 It is the horizon where plants can get most of the
available nutrients from minerals and organic matter.

34. Soil formation begins with weathering of rocks.
2
Weathering is the process of wearing away or breaking
down of rocks into smaller pieces.
● Mechanical weathering is the breaking down of rocks
because of physical processes. The agents of
mechanical weathering are temperature, wind, water,
and living things.
● Chemical weathering is the breaking down of rocks
due to chemical changes that involve water, acids, and
gases like oxygen. It changes the minerals in rocks and
causes new substances to form.
1

35. Tell whether each of the following
statements is true or false.
 Weathering breaks down bedrock.
 Soil is defined as the mixture of rocks and
weathered rocks.
 Carbonic acid is a physical agent of
weathering.
 Rust can weather rocks.
 Plants change soil into organic matter.

36. Which is more useful
in soil formation,
mechanical or
chemical weathering?
Why?