HWA CHONG INSTITUTION
Sec 3 IHE - Geography
Worksheet 1 – Landforms resulting from Vulcanicity
Name: ________________________ (
1
)
Class: 3___
Study Fig. 1 which shows convergent plate movement.
Fig. 1
Based on the diagram above, explain how volcanoes are
formed.
Sec 3 IH Elective/BSC/2009/Chan ML
[5]
Fig. 2 shows the hazard map and diary excerpts of the 1997
eruption of the Soufriere Hills Volcano.
Diary excerpts – Soufriere Hills Volcano 1997
June 25/26
Most devastating flow down NE slopes of volcano.19 people
killed who had returned to their homes in the danger
zone.9000m high eruption cloud.
August
Pyroclastic flows and lahars destroy Plymouth, Montserrat’s
capital 3 miles from crater.
September
Flows destroy Bramble airport 3.5 miles from crater.
November
Ash and tephra fall
December
Pyroclastic flows down the White River valley. Eruption
clouds up to 36,000 feet
Fig. 2
2
a)
I – What is a pyroclastic flow?
II- Describe and explain the effects of the 1997 eruption on
the physical and human landscape.
IIIWhy do volcanoes like the Soufriere Hills erupt so
violently?
IV- With reference to named examples, assess the benefits
of near volcanic areas.
Sec 3 IH Elective/BSC/2009/Chan ML
[1]
[5]
[3]
[5]
MARKING SCHEME
1
2
Based on the diagram above, explain how volcanoes are
formed.
 Convergence of an oceanic and continental plate
 When the thinner and denser oceanic plate converges
 with a thicker and lighter continental plate
 Oceanic plate is subducted and
 Destroyed at the uppermost mantle
 The heat at the depth produces silica-rich magma;
 Which moves upwards through breaks or fractures,
 Escaping through vents,
 To the earth’s surface as lava
 it solidifies and accumulates, forming a volcano
a)
[5]
I – What is a pyroclastic flow?
[1]
 fast-moving flow of hot gas (1,000 °C) and rock
(collectively known as tephra)
 travelling from the volcano at great speed (700 km/hr).
II- Describe and explain the effects of the 1997 eruption on [5]
the physical and human landscape.
Human
 19 people died
 a number of people became homeless
 jobs were lost
 great impact in the economy as many areas had to be
rebuilt
Physical
 infrastructure such as roads and the airport were
destroyed
 the pyroclastic flows reached Plymouth, the capital
 It chocked the White River, killing marine life but also
 Creating a new delta in the Eastern side of the island
 Destruction of vegetation / farm land by pyroclastic
flow, lava and fire
 Air pollution
III- Why do volcanoes like the Soufrie Hills erupt so violently? [3]
 Soufriere Hills is a composite volcano,
 Viscous lava solidified in the central pipe,
 Blocking the passageway,
 with the rise of magma and trapped gases, tremendous
pressure was suppressed
 When it could no longer suppress this pressure, an
immense explosive eruption of ash and cinder
occurred.
Sec 3 IH Elective/BSC/2009/Chan ML

The resulting explosions rose vertically (as much as 9
miles) – from the Reading list
IV- With reference to named examples, assess the benefits [8]
of near volcanic areas.
L1
1-3
 Answer limited to description of benefits,
 No examples
L2
 More detailed description of benefits
 General examples
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4-6
L3
7-8
Benefits dealt with in detail
Specific examples
Fertile soil that will be formed after lava and pyroclastic
materials are weathered
Farmers can reap rich harvest
Gunong Merapi (Central Java)
Presence of precious stones and minerals such as
silver, gold, diamon, copper, lead and zinc
Kimberley (S. Africa)
Tourism: source of revenue
Hotsprings, geysers,
Yellowstone National Park (USA). Mt. Fuji (Japan)
Geothermal energy driving turbines to generate
electricity
Iceland, Japan
Sec 3 IH Elective/BSC/2009/Chan ML