Chapter 8 Landforms of the earth credits to Marshall Cavendish Education

1. Chapter 8
Landforms on the Earth

2. The earth surface
• Earth’s surface is not flat or smooth. It has been shaped and changed
into many different features over years
• Made up of many different landforms.

3. Types of Landforms

4. Mountain
• Usually taller than 600 m in
height with steep slopes and a
narrow top or peak

5. Hill
• Usually less than 600m in
height, rounded in shape with
gentle slopes

6. Valley
• A low area of land between hills
or mountains

7. Plain
• A broad, flat and low area on the
Earth’s surface

8. Plateaux
• A raised area of land, usually flat
with a broad top and steep slopes
• another type of landform
associated with vulcanicity
• A plateau is formed when a large
quantity of magma escapes from a
fault in the Earth’s crust and
spreads over a wide area
• Layers of hardened lava form a
plateau

9. Volcanoes
• a mountain or hill, typically
conical, having a crater or
vent through which lava, rock
fragments, hot vapor, and gas
are being or have been
erupted from the earth's crust.
• Volcanoes commonly occur at
the boundaries of plates
where the impact of plate
movements is the greatest

10. The internal structures of
the Earth
Layers of the Earth

11. The Core
• Centre of the earth
• Temperature of up to 5 000 Degrees Celsius
• Solid due to intense pressure exerted on the center by the outer layers
of the Earth.

12. The Mantle
• Layers of rock that surrounds the core
• 2 900 km in thickness
• 80% of the earth total volume
• Temperature 2 000 degrees Celsius
• Semi-molten or semi-liquid state

13. The Crust
• Outermost layer of the earth
• Solid state
• Varies in thickness 6 to 7 km
• Made up of several pieces called plates which floats on the semimolten mantle beneath them

14. The Internal Structure of The Earth
• Core: the centre of the Earth
• Mantle: the layer above the core
and makes up nearly 80% of the
Earth’s total volume
• Crust: the outermost layer
which is made up of many
separate pieces called plates

16. Internal Forces That
Create Landforms
Folding, Vulcanicity

17. Internal Forces that Create Landforms
• The Earth’s plates are always
moving
Ocean
Plate
• The movement of plates is
known as crustal movement
Mantle
• As the plates move, they may
slide past, pull apart from or
push towards each other,
resulting in the creation of many
landforms on the Earth
Ocean
Plate
Mantle
Plate
Plate

18. Folding
• Some plates collide with each other
• When this happens, some of the
layers of rocks buckle and form
folds
• When the amount of folding is
large, mountains may form
• Examples of fold mountains:
•
The Himalayas
•
The Appalachian Mountains
•
The Andes
•
The Alps
Some plates push towards
each other and form folds

19. Vulcanicity
• When the temperature beneath
the Earth’s surface is so great,
magma (molten mantle) is
formed
• Magma that reaches the Earth’s
surface is called lava
• Vulcanicity is the process in
which magma and other
materials reach the Earth’s
surface

20. Vulcanicity
• The outpouring of the lava onto
the Earth’s surface is called an
eruption
• At the Earth’s surface, the lava
hardens due to the cooler
temperature
• Hardened lava from eruptions
through a single hole or vent
may result in a cone-shaped
mountain called a volcano

21. Volcanoes
• A volcano consists of a vent,
pipe, crater and cone:
 Vent: An opening in the Earth’s
surface
 Pipe: A channel which allows
the magma to rise to the top of
the volcano during an eruption
 Crater: A bowled-shaped
opening at the top of the
volcano
 Cone: The shape of the volcano

22. Volcanoes
•
Volcanoes commonly occur at the
boundaries of plates where the impact of
plate movements is the greatest
•
There are three types of volcanoes:

Active volcano: erupted from time to time and will
most likely erupt again in future
- e.g. Mount St Helens, USA

Dormant volcano: presently inactive but may erupt
again
- e.g. Mount Rainer, USA

Extinct volcano: unlikely to erupt again
- e.g. Mount Kilimanjaro, Tanzania

23. External Forces that
Modify Landforms
Weathering

24. Weathering
• Weathering refers to the process by which rocks are progressively
broken down into fragments where they are
• Weathering is mainly caused by:
 Large changes in temperature
 Action of water
 Action of freezing water
 Plant growth

25. Cracks appearing on a
Weathering - Large changes in temperature of changes
rock because
in temperature
 Heat causes the surface layer of
the rock to expand during the
day
 During the night, the surface of
the rock cools and contracts
faster than the interior of the
rock
 This constant expansion and
contraction weakens the surface
of the rock

26. Weathering – Action of water
 Rainwater combines with carbon
dioxide in the air to form
carbonic acid which dissolves
certain types of rocks such as
limestone
How would you
describe the
formation of the
physical features of
this limestone cave?

27. Weathering -Action of freezing water
 Water from melting snow or
rain may enter cracks in rocks
 When water freezes, it
expands and causes the
cracks in the rocks to widen
Can you describe
how the action of
freezing water has
caused the physical
features of this
mountain?

28. Weathering - Plant growth
 The wind may carry seeds of
plants into the cracks in rocks
 As the seeds grow into plants,
the roots grow into the rocks
and force the cracks in the
rocks to widen
 Overtime, the rocks can fall
apart if the force is strong
enough

29. Erosion
• Erosion refers to the process of wearing down surface materials and
moving them from one place to another
• Erosion is mainly caused by:
 Action of running water
 Action of waves
 Action of wind

30. Erosion - Action of running water
Running Water
 Water in streams and rivers
carries a lot of sediments or
small particles
 The sediments in the water
wears down rocks as the water
flows over them
 The action of the water and its
sediments will gradually erode
the Earth’s surface

31. Erosion - Action of waves
 The constant breaking of
waves against the shore,
together with the grinding
action of sand and stones in
the waves, erodes the
seashore
 It results in landforms such as
sandy beaches, caves and
cliffs
Waves

32. Erosion - Action of wind
 Wind erosion occurs in areas
with little water and few plants to
hold the soil in place
 Strong winds carry large
amounts of sand which wear
away the surfaces of rocks in
their path
 Erosion tends to take place
mainly at the base of rocks
Wind

33. How Do Landforms Affect Us?
• Location of homes
 The relief of the land affects
where people build their
settlements
 People living near volcanoes
and areas which are prone to
floods bear the risk of losing
their lives and property when
disaster strikes
This picture shows
how people are
able to build houses
even on the slopes
of a hill

34. How Do Landforms Affect Us?
• Human activities
 People have adapted to the
environment by cutting terraces
into the slopes to grow crops
 Recreational activities such as
trekking and mountain climbing
take place on hills and mountains
 Scenic places attract both local and
foreign tourists