Download Answer skills

NSS Geography
Writing a short essay / Page 1
Tips on Tackling Essay Questions
1. First, circle the question words such as Describe, Explain, Discuss, Compare and
Contrast, Give examples, Evaluate etc.
2. Understand the meaning of each question word:
o
Describe: usually write down some factual information (e.g. temperature of TRF,
annual rainfall of tropical deserts)
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Explain: to make known in detail - facts are most important
o
Account for: state the reason for
o
Discuss: Describe and explain, write about the various opinions and ideas about
the subject
o
Compare: Write down both the similarities and the differences.
o
Contrast: Write down the differences.
o
Examine: divide into parts and analyze each part or investigate each part
o
Assess: estimate the value of ……
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Give examples: Be careful with the words example and example(s) and which
examples (e.g. more developed countries or less developed countries?)
o
Evaluate: Not only mention the solutions to the problem but also write down the
effectiveness of the solutions.
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Evaluate the validity of a statement: this is a warning to the student that the
statement may, or may not, be accurate or complete
3. Introduction and Conclusion: It will give the marker a better impression if you can write
a short introduction and a conclusion.
4. Write neatly and in a systematic way
5. Leave spacing between paragraphs
6. Draw diagrams to illustrate the text where necessary e.g. Plate Tectonics, river profile etc.
What is the major landform features associated with mountain building processes? With
appropriate examples, show how the theory of Plate Tectonics helps to explain the location of
this landform. Give an account for the related natural hazard in these regions.
Strength:
• Can include all the landform features associated with mountain building processes such
as block mountain
• Good examples and diagrams
• Can relate the formation of landforms with the theory
Outline
Definition of Plate Tectonics theory
Along constructive plate boundary: mid oceanic ridge
Along destructive plate boundary: island arcs, volcanoes, fold mountains (continental plate
collides with continental plate and continental plate collides with oceanic plate), block mountain
Natural hazards: earthquake, tsunamis, volcanic eruptions
NSS Geography
Writing a short essay / Page 2
Full answer
Many major landform features are associated with mountain building processes. The Plate Tectonics
theory states that the lithosphere is broken into lithospheric plates consisting of continental crust, oceanic
crust and the rigid upper mantle. The lithospheric plates float and move over the asthenosphere. The
movement of plates usually results in mountain building and volcanic activities. The driving force for the
plate movement is the convective currents in the magma located deep in the asthenosphere.
Landforms are formed along both constructive and destructive boundaries. Along constructive plate
margins, plates move apart because of the rising convective currents of magma in the asthenosphere. A
fissure develops, allowing hot, molten rock to swell up from the mantle to form new crust as it solidifies.
Mid-oceanic ridges are formed when mantle convective currents break up the ocean floor. The best
explored and perhaps the best developed topographically is the Mid-Atlantic Ridge.
Island arcs are chains of volcanic islands formed along the boundary where two or more oceanic plates
collide or an oceanic plate collides with the continental plate. Along the destructive plate margin, an
oceanic plate collides with a continental plate as a result of descending convective currents of magma. The
oceanic plate subducts beneath the continental plate and rock materials in the oceanic plate melt. An
ocean trench is formed and fissures are created as the plate sinks into the asthenosphere. The melted
material of the oceanic plate is lighter than the mantle and so it rises to the surface through fissures to
form chains of volcanic island arcs, for example, the Ryukyu Islands where the Pacific Plate collides with
the Eurasian Plate.
A special case of vulcanicity is the hot spot volcanoes. It is found in the interior of plates, for example,
Mauna Loa Volcano in Hawaii, where plumes of hot material rises through the thin oceanic crust from
the mantle resulting in the formation of volcanic islands. Volcanic islands give rise to volcanic eruption.
Tectonic activities may also lead to the formation of Fold Mountains. There are two types of Fold
Mountains. Converging of an oceanic crust and a continental crust produces one type of Fold Mountains
such as Andes. The South American Plate (continental plate) collided with the Nazca Plate (oceanic plate)
as sinking convective currents pulled them towards each other. The continental plate and the oceanic
plate are of different densities. The denser Nazca Plate subducted under the South American Plate.
Subduction produced a deep trench on the ocean floor (i.e. Peru-Chile Trench). The denser Nazca Plate
melted into molten rock. The sedimentary rocks formed between them were compressed and folded to
form a chain of Fold Mountains (i.e. Andes). Volcanoes can be found in the Fold Mountains.
Another type of Fold Mountains is formed by the collision of one continental plate with another
continental plate. An example of this type of Fold Mountains is the Himalayas. The Eurasian Plate
(continental plate) collided with the Indian Plate (continental plate) along the destructive plate margin.
As both of them are continental plates, they are of equal density. No subduction occurred. The
sedimentary rocks formed in the ancient sea were compressed and folded to form the Himalayas in the
interior of the continent of Asia.
Block mountain is the relatively uplifted block produced by faulting between two fault scarps. It is formed
by compress ional or tensional forces. The rock mass is left standing when the crust on either side of a
pair of faults subsides. It can also be formed when a central rock mass is thrust upwards between a pair
of faults. A famous example of Block mountain is the Deccan Plateau in the southern part of Africa. Block
mountains are usually found along constructive plate margins.
Natural hazards such as earthquakes, tsunamis and volcanic eruption may occur in these regions. It is due
to plate movements caused by convective currents.
Earthquake is a sudden and massive fracturing and breaking of rock along a distinct failure plane. This
failure plane tends to develop where stresses within the rock are the greatest. If stress is maintained long
enough, the rock will fracture along a fracture plane. The stress is released and the ground shakes.
Tsunamis are often generated in the ocean at a point near the earthquake source by a sudden movement
of the sea floor due to tectonic processes. This frequently brings about exceedingly high tide and flooding
to the coastal regions.
Volcanic eruption occurs when there is release of pressure in the earth's crust. Molten magma seeks its
way through lines of weakness in the crust. Volcanic eruptions occur both in constructive plate margins
and in destructive plate margins.