Convergent plate boundaries occur where tectonic plates move towards one another. There are three main types: 1) Oceanic-oceanic, where two oceanic plates collide and one subducts under the other, forming ocean trenches. 2) Oceanic-continental, where an oceanic plate subducts under a continental plate, pushing up mountains. 3) Continental-continental, where collision resists subduction and the plates break and fold, forming mountains.

1. CONVERGENTPLATES

2. CONVERGENT PLATE BOUNDARIES
• Two plates moving towards each other and
collides
• Denser (heavier) plate will go below the less
dense (lighter) plate
• Process is called SUBDUCTION
• Subducted plate sinks into the mantle and melts
due to high heat

3. 1. Convection current
2. Slab pull force
Why do tectonic plates move?
Plates moving away from each other
Platesmoving
towardseachother
Plates
moving
towards
eachother
Plates
Ocean floor

4. REVISION
1. Convection currents
•Convection currents are movements of
heat within the mantle.
•Material in the mantle is heated by the
core.
•Mantle expands, rises and spreads out
beneath the plates.
•Plates are dragged along and move away
from each other. (DIVERGENT PLATES)

5. • When denser plate
subducts under less
dense plate
• It pulls the rest of
the plate along
• The subducting
plate drives the
downward-moving
portion of
convection
currents.
2. Slab-pull force

6. Oceanic trench

7. Fold mountains
• Over millions of years, the folding of rocks creates a
landform called fold mountains.
• The Himalayas, the Rocky Mountains and the Andes
are examples of fold mountains.

8. Fold mountains
The Himalayas
Peak : Mount Everest (between
Nepal and Tibet)
Elevation : 8,848 metres
• The compressional force
causes the layers of rocks
to buckle and fold.
• This process is known as
folding.

9. P54 Q8
P54

10. • 2m (diagram) , 0.5m for each point below
• Two continental plates may collide with one
another, resisting subduction.
• This causes the plates to break and slide along
fractures in the crusts.
• When continental Eurasian plate converge with
continental Indian plate,
• the crusts are compressed and they fold upwards
or sideways to form fold mountains
8 With the aid of a well-labelled diagram, explain the
formation of fold mountains at a continental-continental
plate boundary. [4]

11. • The upfold is called the anticline and
• The downfold is the syncline.
Fold mountains

12. • When there is increasing compressional force on one limb
of a fold, the rocks may buckle until a fracture forms.
• The limb may then move forward to ride over the other
limb
Fold mountains

13. • Fold mountains are located along convergent plate
boundaries
QUIZ! Fold mountains

14. Label Mountains A - H

15. HomeWork – P56
With the aid of a well-labelled diagram,
account for the formation of the Mariana
Islands and the Mariana Trench. [5]
–Diagram 2 marks
•0.5m for each labelling/drawing
–Explanation 3 marks
•0.5m for each point

16. Convergent plate boundaries
1. Oceanic–oceanic plate convergence
2. Continental–oceanic plate convergence
3. Continental–continental plate convergence

17. CONVERGENTPLATES

18. 1. Oceanic–Oceanic plate convergence
E.g. the Pacific Plate converging with the slower-moving
Philippine plate. Earthquakes may also occur.

19. P56 With the aid of a well-labelled diagram, account for
the formation of the Mariana Islands and the Mariana
Trench. [5]
-Diagram 0.5m each
-Subducted plate, ‘Mariana Trench’, ‘Mariana Islands’,
Magma rising

20. P56 With the aid of a well-labelled diagram, account for
the formation of the Mariana Islands and the Mariana
Trench. [0.5m each]
a) As the magma cools and sinks, the Pacific plate and the
Philippines plates are pulled together/converge.
b) When the two oceanic plates converge, the denser
Pacific plate subducts under the Philippines.
c) A subduction zone forms, creating a deep oceanic
trench (Mariana Trench).
d) The subduction of the oceanic plate causes the solid
mantle material to melt and magma is formed.
e) The magma rises through the mantle and ocean floor
to emerge as volcanoes.
f) Eventually a chain or arc of volcanic islands called
island arc is formed (Mariana Islands).

21. 2.Oceanic-continental plate convergence
E.g. the Australian Plate subducting under a section of the
Eurasian Plate near Sumatra formed the Sunda Trench.

22. 2.Oceanic-continental plate convergence

23. QUIZ 1 P55
With the help of Fig. 8, describe the phenomenon and the
formation of its resultant landforms. [5]

24. With the help of Fig. 8, describe the phenomenon
and the formation of its resultant landforms. [5]
• The oceanic crust and the continental crust are
__________________ towards each other.
• The denser and heavier oceanic crust
_______________ into the mantle and melts into
magma under the high heat.
• A long, narrow and deep depression called an
_____________is formed at the subducted zone.
• Magma rises up the factures caused by the plate
convergence and ____________to form volcanoes.
• Over time, more and more volcanoes build up to
form a volcano ________.

25. P55
With the help of Fig. 8, describe the phenomenon and the
formation of its resultant landforms. [5]
• The oceanic crust and the continental crust are
converging/moving towards each other.
• The denser and heavier oceanic crust
sinks/subducts into the mantle and melts into
magma under the high heat.
• A long, narrow and deep depression called an
oceanic trench is formed at the subducted zone.
• Magma rises up the factures caused by the plate
convergence and cools and solidifies to form
volcanoes.
• Over time, more and more volcanoes build up to
form a volcano arc.

26. 3. Continental – continental convergence
Continental crust
Continental crust
Himalayas
Tibetan
Plateau
Uppermost mantle
Asthenosphere
EURASIAN
PLATE
INDIAN
PLATE
E.g. the Himalayas -
convergence of the
Indian Plate and the
Eurasian Plate.

27. 3. Continental-continental plate convergence
a) Plates made largely of continental crust
may collide with other plates made
largely of continental crust.
b) However, both plates have similar
densities and hence, resist subduction.
c) Instead, the plates break, slide along
fractures in the crust and fold, forming
fold mountains.

28. Classwork
P54 Q9
SCGS PRELIMS 2014
Explain how the plate movement taking place at
a continental-oceanic plate boundary may
produce fold mountains. [4]

29. P54 Explain how the plate movement taking place at
a continental-oceanic plate boundary may produce
fold mountains. [4]
•When an oceanic plate converges with a
continental plate
•The denser oceanic plate subducts under the less
dense continental plate
•As the continental plate rode over the oceanic
plate, the sediment on the ocean floor buckled and
crumpled
•This cause an uplift of the crust into the fold
mountains